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Neural Communication Patterns Underlying Conflict Detection, Resolution, and Adaptation
Abstract
In an ever-changing environment, selecting appropriate responses in conflicting situations is essential for biological survival and social success and requires cognitive control, which is mediated by dorsomedial prefrontal cortex (DMPFC) and dorsolateral prefrontal cortex (DLPFC). How these brain regions communicate during conflict processing (detection, resolution, and adaptation), however, is still unknown. The Stroop task provides a well-established paradigm to investigate the cognitive mechanisms mediating such response conflict. Here, we explore the oscillatory patterns within and between the DMPFC and DLPFC in human epilepsy patients with intracranial EEG electrodes during an auditory Stroop experiment. Data from the DLPFC were obtained from 12 patients. Thereof four patients had additional DMPFC electrodes available for interaction analyses. Our results show that an early θ (4-8 Hz) modulated enhancement of DLPFC γ-band (30-100 Hz) activity constituted a prerequisite for later successful conflict processing. Subsequent conflict detection was reflected in a DMPFC θ power increase that causally entrained DLPFC θ activity (DMPFC to DLPFC). Conflict resolution was thereafter completed by coupling of DLPFC γ power to DMPFC θ oscillations. Finally, conflict adaptation was related to increased postresponse DLPFC γ-band activity and to θ coupling in the reverse direction (DLPFC to DMPFC). These results draw a detailed picture on how two regions in the prefrontal cortex communicate to resolve cognitive conflicts. In conclusion, our data show that conflict detection, control, and adaptation are supported by a sequence of processes that use the interplay of θ and γ oscillations within and between DMPFC and DLPFC.
... For example, the effect of increased sensory load, imposed by competing/degraded speech, resulted in increased or decreased alpha power (Obleser and Weisz, 2012;Wöstmann et al., 2015;Dimitrijevic et al., 2017;Wisniewski et al., 2021). The effect of increased cognitive load on neural oscillations has been studied using a variety of tasks Wilsch and Obleser, 2016;Hjortkjaer et al., 2020;Beldzik et al., 2022), however, only few studies utilized the auditory Stroop task (Oehrn et al., 2014;van de Nieuwenhuijzen et al., 2016;Sharma et al., 2021). These studies suggested frontal theta power as an index of conflict processing, showing enhancement to incongruent vs congruent stimuli, even when behavioral manifestations were not observed (Sharma et al., 2021). ...
... These studies suggested frontal theta power as an index of conflict processing, showing enhancement to incongruent vs congruent stimuli, even when behavioral manifestations were not observed (Sharma et al., 2021). Additionally, during conflict processing an interplay between theta and gamma oscillations in prefrontal brain regions was evident (Oehrn et al., 2014). ...
... Previous studies in the visual modality demonstrated increased theta power during conflict processing (Kerns et al., 2004;Hanslmayr et al., 2008;Ergen et al., 2014). Reports regarding the auditory version of the Stroop task show similar effects, although to a much lesser extent (Oehrn et al., 2014;van de Nieuwenhuijzen et al., 2016). ...
... The lower theta oscillation was observed in incongruent trials than in congruent trials only after the rDLPFC stimulation. In the Stroop task, frontal theta oscillations were often associated with the detection of interference and inhibition of responses to task-irrelevant features (Eschmann et al. 2018;Hanslmayr et al. 2008;Itthipuripat et al. 2019;Oehrn et al. 2014;Tang et al. 2013). ...
... The gamma oscillations were related to cognitive control, with greater power when cognitive control is stronger (Farzan et al. 2009(Farzan et al. , 2012). In the Stroop task, higher gamma oscillations were reported after incongruent trials (Bartoli et al. 2018), and post-response gamma power in a conflicting trial predicted shorter RTs in an upcoming conflict trial (Oehrn et al. 2014), which suggests that gamma oscillations after responses are related to the adjustment of cognitive control to conflict. Thus, the current results may indicate that the rDLPFC stimulation influences the cognitive control adjustment to conflict. ...
... The consistent or individually calibrated stimulation intensities could be considered for future studies. Third, previous studies found that neural communication patterns played an important role in conflict processing (Bartoli et al. 2018;Oehrn et al. 2014), whereas the current study only explored the effects of the rDLPFC stimulation on conflict processing with ERP and time-frequency analyses. Future studies could consider neural communication analysis to achieve a comprehensive understanding of conflict processing. ...
Conflict typically occurs when goal-directed processing competes with more automatic responses. Though previous studies have highlighted the importance of the right dorsolateral prefrontal cortex (rDLPFC) in conflict processing, its causal role remains unclear. In the current study, the behavioral experiment, the continuous theta burst stimulation (cTBS), and the electroencephalography (EEG) were combined to explore the effects of behavioral performance and physiological correlates during conflict processing, after the cTBS over the rDLPFC and vertex (the control condition). Twenty-six healthy participants performed the Stroop task which included congruent and incongruent trials. Although the cTBS did not induce significant changes in the behavioral performance, the cTBS over the rDLPFC reduced the Stroop effects of conflict monitoring-related frontal-central N2 component and theta oscillation, and conflict resolution-related parieto-occipital alpha oscillation, compared to the vertex stimulation. Moreover, a significant hemispheric difference in alpha oscillation was exploratively observed after the cTBS over the rDLPFC. Interestingly, we found the rDLPFC stimulation resulted in significantly reduced Stroop effects of theta and gamma oscillation after response, which may reflect the adjustment of cognitive control for the next trial. In conclusion, our study not only demonstrated the critical involvement of the rDLPFC in conflict monitoring, conflict resolution processing, and conflict adaptation but also revealed the electrophysiological mechanism of conflict processing mediated by the rDLPFC.
... Threat sensitivity and MF theta MF theta may be an important neural mechanism to consider when investigating performance monitoring and ST. MF thetaband oscillations are a robust marker of performance monitoring and conflict detection (Cavanagh and Frank, 2014;Oehrn et al., 2014;van Noordt et al., 2016). For example, MF theta is sensitive to conflict detection during tasks that involve competing response conflicts (Oehrn et al., 2014) and behavioral adjustments following error commissions (Kalfaog lu et al., 2018). ...
... MF thetaband oscillations are a robust marker of performance monitoring and conflict detection (Cavanagh and Frank, 2014;Oehrn et al., 2014;van Noordt et al., 2016). For example, MF theta is sensitive to conflict detection during tasks that involve competing response conflicts (Oehrn et al., 2014) and behavioral adjustments following error commissions (Kalfaog lu et al., 2018). ...
... The goal of the current study was to assess whether a neural indicator of cognitive control, MF theta differentiation, was associated with longitudinal trajectories of sensitivity to threat. MF theta dynamics represent a common neural signature of the instantiation of cognitive control and performance monitoring (Cavanagh and Frank, 2014;Oehrn et al., 2014). Hypervigilant performance monitoring is thought to be an important behavioral characteristic of individuals with heightened sensitivity to threat, and thus, understanding the dynamic interplay between hypervigilant performance monitoring and sensitivity to threat may be important to identify youth who are Each class's distribution for theta power is presented to the right of the box plots. ...
Sensitivity to threat is thought to be a hallmark of the onset and maintenance of anxiety, which often manifests behaviorally as withdrawal, increased arousal, and hypervigilant monitoring of performance. The current study investigated whether longitudinal trajectories of sensitivity to threat were linked to medial frontal theta power dynamics, a robust marker of performance monitoring. Youth (N = 432, Mage = 11.96 years) completed self-report measures of threat sensitivity annually for three years. A latent class growth curve analysis was used to identify distinct profiles of threat sensitivity over time. Participants also completed a GO/NOGO task while EEG was recorded. We identified three threat sensitivity profiles:(1) high (N = 116), (2) moderate (N = 241), and (3) low (N = 74). Participants in the high threat sensitivity class had greater levels of medial frontal theta power differentiation (NOGO-GO) compared to participants in the low threat sensitivity class, indicating that consistently high threat sensitivity is associated with neural indicators of performance monitoring. Of concern, both hypervigilant performance monitoring and threat sensitivity have been associated with anxiety; thus, youth with high threat sensitivity may be at risk for the development of anxiety.
... Thus, these areas could either represent the strength of the harm aversion motive by itself, or they could be involved in processing/resolving the conflict between concerns about inequality and harm. The latter interpretation may be in line with previous findings that DMPFC/ACC, IFG, and MFG are often activated during cognitive control, conflict resolution, or behavioral adaptation (De Wit et al., 2006;Oehrn et al., 2014;de Kloet et al., 2021); and that TPJ is thought to be involved in mentalizing and perspective taking (Badre and Wagner, 2004;Van Overwalle, 2009;Oehrn et al., 2014;Hill et al., 2017). However, none of the neural effects in these areas were associated with the strength of behavioral harm aversion or inequality aversion, or the probability to choose the more equal offer in the critical condition. ...
... Thus, these areas could either represent the strength of the harm aversion motive by itself, or they could be involved in processing/resolving the conflict between concerns about inequality and harm. The latter interpretation may be in line with previous findings that DMPFC/ACC, IFG, and MFG are often activated during cognitive control, conflict resolution, or behavioral adaptation (De Wit et al., 2006;Oehrn et al., 2014;de Kloet et al., 2021); and that TPJ is thought to be involved in mentalizing and perspective taking (Badre and Wagner, 2004;Van Overwalle, 2009;Oehrn et al., 2014;Hill et al., 2017). However, none of the neural effects in these areas were associated with the strength of behavioral harm aversion or inequality aversion, or the probability to choose the more equal offer in the critical condition. ...
... Evidence from two different lines of research supports such a modulating role of DMPFC for the trade-off between motives. On the one hand, DMPFC, together with adjacent regions ACC, is critical engaged in conflict monitoring, conflict resolution, and action selection in a variety of cognitive tasks (Badre and Wagner, 2004;De Wit et al., 2006;Oehrn et al., 2014;de Kloet et al., 2021), which may support the resolution of conflict between different motives in the current paradigm (i.e., suppressing motive of equality pursuing). On the other hand, DMPFC is also thought to be part of the mentalizing system that supports vicarious experiences of others' pain or . ...
In the history of humanity, most conflicts within and between societies have originated from perceived inequality in resource distribution. How humans achieve and maintain distributive justice has therefore been an intensely studied issue. However, most research on the corresponding psychological processes has focused on inequality aversion and has been largely agnostic of other motives that may either align or oppose this behavioral tendency. Here we provide behavioral, computational, and neuroimaging evidence that distribution decisions are guided by three distinct motives - inequality aversion, harm aversion, and rank reversal aversion - that interact and in fact can also deter individuals from pursuing equality. At the neural level, we show that these three motives are encoded by separate neural systems, compete for representation in various brain areas processing equality and harm signals, and are integrated in the striatum, which functions as a crucial hub for translating the motives to behavior. Our findings provide a comprehensive framework for understanding the cognitive and biological processes by which multiple prosocial motives are coordinated in the brain to guide redistribution behaviors. This framework enhances our understanding of the brain mechanisms underlying equality-related behavior, suggests possible neural origins of individual differences in social preferences, and provides a new pathway to understand the cognitive and neural basis of clinical disorders with impaired social functions.
... Conflict monitoring, or interference control, is a key cognitive control operation which allows us to flexibly adjust thoughts, emotions, or actions in response to interfering or conflicting streams of information (Allport, 1980, Miller & Cohen, 2001Navon & Miller, 1987;Norman & Shallice, 1986). The conflict monitoring hypothesis is an influential theory proposed by Botvinick et al. (2001) which suggests that competing representations or actions trigger a conflict monitoring system unfolding a cascade of hypothesized processes: i) conflict detection, ii) conflict resolution via action selection and selective suppression, and iii) post-response adaptation to prepare for the next trial (Botvinick et al., 2001;Mansouri et al., 2009;Oehrn et al., 2014). Numerous paradigms have been employed to examine conflict monitoring in an experimental context, typically by comparing congruent and incongruent stimulus/ response features. ...
... In the low beta band (12-20 Hz), ERS was observed on the Animals task (higher in the positive direction) compared to ERD on the Objects task (higher in the negative direction). This differentiation in low beta occurred at the earliest time period (0-100 ms), during the perceptual encoding/detection stage of conflict monitoring (Oehrn et al., 2014). This likely reflects differences in early visual processing of Objects versus Animals, as differences in perceptual processing have been noted between these two cateogires (Bozeat et al., 2003;Caramazza & Mahon, 2003;Collins & Olson, 2014). ...
... Thus, the rLPFC's role for moderating aversion to disadvantageous or advantageous inequity is far from understood. Further, even though previous research suggests that control processes in the rLPFC during negative feedback and conflict processing are associated with theta oscillations (van de Vijver et al., 2011;Oehrn et al., 2014), the specific brain rhythms underlying the rLPFC's role for conflicts between fairness-guided behaviour and selfish interests remain unknown. ...
... More specifically, we expected rTPJ tACS to increase advantageous inequity (Morishima et al., 2012;Soutschek et al., 2016;Obeso et al., 2018), but rTPJ stimulation may additionally affect also aversion to disadvantageous inequity if the rTPJ plays a general role for resolving conflicts between selfish and other-regarding interests. Second, we expected that entrainment of theta oscillations in rLPFC reduces aversion to disadvantageous rather than advantageous outcomes due to the involvement of prefrontal theta in cognitive control (van de Vijver et al., 2011;Oehrn et al., 2014). ...
The right temporo-parietal junction (rTPJ) and the right lateral prefrontal cortex (rLPFC) are known to play prominent roles in human social behaviour. However, it remains unknown which brain rhythms in these regions contribute to trading-off fairness norms against selfish interests as well as whether the influence of these oscillations depends on whether fairness violations are advantageous or disadvantageous for a decision maker. To answer these questions, we used non-invasive transcranial alternating current stimulation (tACS) to determine which brain rhythms in rTPJ and rLPFC are causally involved in moderating aversion to advantageous and disadvantageous inequity. Our results show that theta oscillations in rTPJ strengthen the aversion to unequal splits, which is statistically mediated by the rTPJ's role for perspective taking. In contrast, theta tACS over rLPFC enhanced the preference for outcome-maximizing unequal choices more strongly for disadvantageous compared to advantageous outcome distributions. Taken together, we provide evidence that neural oscillations in rTPJ and rLPFC have distinct causal roles in implementing inequity aversion, which can be explained by their involvement in distinct psychological processes.
... In terms of the relationship between executive function and language, the DLPFC has frequently been implicated in a range of executive functions necessary for complex language tasks (see [28] for an overview). Broad functions, such as executive control and working memory, as well as more specific functions, such as detecting novelty of incoming information [30,31] and conflict detection, resolution and adaptation [32], have been the focus of studies exploring the connection between the DLPFC and language. Another promising potential link between the DLPFC and the canonical language network is that elaborated timing functions are required for articulatory motor activity to produce a smooth speech signal integrated with the time requirements of cognitive processes such as lexical access, particularly in the case of difficult lexical access [28]. ...
... Producing words, in contrast to comprehending words, requires elaborate timing functions to produce articulatory movements that result in a smooth speech signal integrated with the time requirements of cognitive processes such as lexical access or syntactic processing [28,33]. In our view, this approach, rather than others that implicate detecting novelty of incoming information [30,31] or conflict detection, resolution and adaptation [32], provides a potential explanation for the results obtained in this study. Some recent work may shed light on why producing phonologically but not semantically related words may have played a role in greater activation of the DLPFC. ...
Previous studies suggest that producing and comprehending semantically related words relies on inhibitory control over competitive lexical selection which results in the recruitment of the left inferior frontal gyrus (IFG). Few studies, however, have examined the involvement of other regions of the frontal cortex, such as the dorsolateral prefrontal cortex (DLPFC), despite its role in cognitive control related to lexical processing. The primary objective of this study was to elucidate the role of the DLPFC in the production and comprehension of semantically and phonologically related words in blocked cyclic naming and picture–word matching paradigms. Twenty-one adults participated in neuroimaging with functional near-infrared spectroscopy to measure changes in oxygenated and deoxygenated hemoglobin concentrations across the bilateral frontal cortex during blocked cyclic picture naming and blocked cyclic picture–word-matching tasks. After preprocessing, oxygenated and deoxygenated hemoglobin concentrations were obtained for each task (production, comprehension), condition (semantic, phonological) and region (DLPFC, IFG). The results of pairwise t-tests adjusted for multiple comparisons showed significant increases in oxygenated hemoglobin concentration over baseline in the bilateral DLPFC during picture naming for phonologically related words. For picture–word matching, we found significant increases in oxygenated hemoglobin concentration over baseline in the right DLPFC for semantically related words and in the right IFG for phonologically related words. We discuss the results in light of the inhibitory attentional control over competitive lexical access theory in contrast to alternative potential explanations for the findings.
... Theta oscillations increase in power following response errors ( Holroyd and Coles, 2002, Gehring et al., 2018, Yeung et al., 2004 and negative feedback ( Walsh and Anderson, 2012 ), in response to unexpected events ( Cavanagh et al., 2012 , Mas-Herrero andMarco-Pallarés, 2014 ), during inhibitory control ( Nigbur et al., 2012, Nigbur et al., 2011, when resolving competition between different responses ( Oehrn et al., 2014 ), adjusting response strategies to task demands ( López et al., 2019, McKewen et al., 2020, and following events that are novel or ambiguous in terms of performance feedback ( Sandre andWeinberg, 2019 , Wessel et al., 2012 ). Several studies report that modulation of frontal midline theta (FMT) varies in relation to single trial behaviors, including accuracy ( Cohen and Donner, 2013 ), response adjustments following errors ( Kalfao ğlu et al., 2018 ), reaction times ( McKewen et al., 2020 ), and learning from feedback to adapt future responses ( Cavanagh et al., 2010 ). ...
... Notably, these positive effects on behavior were not solely accounted for by a change in speed versus accuracy tradeoff ( Fusco et al., 2018 ), which is generally linked to the decision threshold parameter, and therefore, consistent with our findings implicating the importance of the starting point bias. These findings contribute to growing evidence of FMT as a robust marker of proactive cognitive control processes ( Cavanagh and Shackman, 2015, Cavanagh and Frank, 2014, Eisma et al., 2021, consistent with a large literature linking FMT oscillations with responses during inhibitory control ( Nigbur et al., 2012, Nigbur et al., 2011, resolution of competing responses ( Oehrn et al., 2014 ) and adjusting response strategies to task demands ( López et al., 2019, McKewen et al., 2020. Taken together, FMT may facilitate proactive cognitive control at the response preparation stage that either directly or indirectly affects one's response style through a bias in the amount of information needed to make a decision under conflict. ...
Frontal midline theta oscillatory dynamics have been implicated as an important neural signature of inhibitory control. However, most proactive cognitive control studies rely on behavioral tasks where individual differences are inferred through button presses. We applied computational modeling to further refine our understanding of theta dynamics in a cued anti-saccade task with gaze-contingent eye tracking. Using a drift diffusion model, increased frontal midline theta power during high-conflict, relative to low-conflict, trials predicted a more conservative style of responding through the starting point (bias). During both high- and low-conflict trials, increases in frontal midline theta also predicted improvements in response efficiency (drift rate). Regression analyses provided support for the importance of the starting point bias, which was associated with frontal midline theta over the course of the task above-and-beyond both drift rate and mean reaction time. Our findings provide a more thorough understanding of proactive gaze control by linking trial-by-trial increases of frontal midline theta to a shift in starting point bias facilitating a more neutral style of responding.
... We focused on the neural activity in the theta band (4-8 Hz) because it constitutes a key component of cognitive control [35][36][37][38] and also in the high-gamma band (70-120 Hz) given its significance in sensory, motor, control, and other cognitive functions. 11,27,[39][40][41] Additional results in other frequency bands (alpha, beta, low-gamma) are reported in Table S8. In previous work, 11 we reported that multiple electrodes showed activity in the high-gamma band that was modulated by the presence of conflict during the Stroop task. ...
... Several previous studies reported signals that differ between incongruent and congruent trials at the level of individual neurons, 28,51 intracranial field potentials, 11,[25][26][27] in scalp electroencephalography signals, 21,23,24 and in functional neuroimaging signals. 8,18,44,45 Most previous studies leveraged a single task, precluding the possibility to assess task invariance and task specificity in conflict modulation. ...
Cognitive control involves flexibly combining multiple sensory inputs with task-dependent goals during decision making. Several tasks involving conflicting sensory inputs and motor outputs have been proposed to examine cognitive control, including the Stroop, Flanker, and multi-source interference task. Because these tasks have been studied independently, it remains unclear whether the neural signatures of cognitive control reflect abstract control mechanisms or specific combinations of sensory and behavioral aspects of each task. To address these questions, we record invasive neurophysiological signals from 16 patients with pharmacologically intractable epilepsy and compare neural responses within and between tasks. Neural signals differ between incongruent and congruent conditions, showing strong modulation by conflicting task demands. These neural signals are mostly specific to each task, generalizing within a task but not across tasks. These results highlight the complex interplay between sensory inputs, motor outputs, and task demands underlying cognitive control processes.
... Thus, these areas could either represent the strength of the harm aversion motive, or they could be involved in processing/resolving the conflict between concerns about inequality and harm. The latter interpretation may be in line with previous findings that DMPFC/ACC, IFG, and MFG are often activated during cognitive control, conflict resolution, or behavioral adaptation (37,38); and that TPJ is involved in mentalizing and perspective taking (39,40). However, none of the neural effects in these areas were associated with the strength of behavioral harm aversion or inequality aversion, or the probability of more equal choice in the Rank-reversal condition. ...
... Evidence from two lines of research supports such a modulating role of DMPFC. First, DMPFC, with adjacent regions ACC, is engaged in conflict monitoring, conflict resolution, and action selection in a variety of cognitive tasks (37,38), which may support the resolution of conflict between different motives in the current paradigm. Second, DMPFC is also thought to be part of the mentalizing system that supports vicarious experiences of others' pain or beliefs (39,56), which may support harm signals in the current paradigm. ...
In the history of humanity, most conflicts within and between societies have originated from perceived inequality in resource distribution. How humans achieve and maintain distributive justice has therefore been an intensely studied issue. However, most research on the corresponding psychological processes has focused on inequality aversion and has been largely agnostic of other motives that may either align or oppose this behavioral tendency. Here we provide behavioral, computational, and neuroimaging evidence that distribution decisions are guided by three distinct motives-inequality aversion, harm aversion, and rank reversal aversion-that interact with each other and can also deter individuals from pursuing equality. At the neural level, we show that these three motives are encoded by separate neural systems, compete for representation in various brain areas processing equality and harm signals, and are integrated in the striatum, which functions as a crucial hub for translating the motives to behavior. Our findings provide a comprehensive framework for understanding the cognitive and biological processes by which multiple prosocial motives are coordinated in the brain to guide redistribution behaviors. This framework enhances our understanding of the brain mechanisms underlying equality-related behavior, suggests possible neural origins of individual differences in social preferences, and provides a new pathway to understand the cognitive and neural basis of clinical disorders with impaired social functions.
... Elles favorisent l'intégration des entrées thalamo-corticales et la détection des conflits. En effet, de nombreusesétudes montrent son augmentation immédiatement après l'apparition de stimuli conflictuels (e.g., NoGo) ou d'erreurs, une augmentation qui reflète le besoin de contrôle Ishii et al., 2014 ;Oehrn et al., 2014). ...
... (2) l'excitation des processus pertinents pour la tâche est rendue possible grâceà l'activation des aires corticales pertinentes pour la réalisation de la tâche via les oscillations gamma (>30 Hz). Par exemple, une augmentation de la puissance gamma aété rapportée au niveau du DLPFC après l'identification d'un conflit (Oehrn et al., 2014), au niveau du cortex pariéto-occipital lors de tâches visuelles (Akimoto et al., 2013 ;Reinhart et al., 2011) ou encore au niveau des cortex temporaux lors des tâches auditives (Ahveninen et al., 2013 ;Potes et al., 2014). ...
L’objectif de ce travail de thèse était d’avancer sur les mécanismes de contrôle cognitif associés aux fluctuations attentionnelles. A cette fin, nous nous sommes appuyés sur différentes méthodologies pour distinguer des périodes d’attention optimale et suboptimale (sur la base de la variabilité intra-individuelle du temps de réaction, du rapport subjectif des sujets ou encore en isolant des périodes de lapses d’attention soutenue). Nos résultats révèlent que les périodes d’attention optimale étaient associées à un engagement des modes de contrôle proactif et réactif chez les sujets sains alors que chez les sujets inattentifs et les patients souffrant de schizophrénie, ces périodes étaient associées au seul engagement du mode de contrôle réactif. Durant les périodes d’attention suboptimale, chez les sujets sains, le désengagement du seul mode de contrôle proactif révèle le rôle central joué par le cortex préfrontal dorsolatéral dans les fluctuations attentionnelles. Chez les sujets inattentifs et les patients schizophrènes, c’est davantage le cortex préfrontal médian, sous-tendant les mécanismes de contrôle réactif, qui serait impliqué.
... This technique has been proven to boost cognitive performance by enhancing the transfer of information among anatomically and functionally connected brain areas, which improve cognitive processes when the current is applied at specific oscillatory frequencies that concur with the endogenous regional synchronization involved in such cognitive functions. Both theta and alpha activity within the frontoparietal control network have been associated with either an increase or a decrease of cognitive control which is thought to be crucial for vigilance [29][30][31][32][33][34][35][36][37][38][39][40] . Congruently, and in accordance with oscillatory models of sustained attention 20,28 , previous tACS studies on sustained attention stimulated at these two frequencies. ...
... In the SART, digits from 1 to 9 appeared in the center of the screen and participants had to press a button in response to all digit except the digit 3. Digits appeared in different font sizes (18,27,36,45, or 54 points) for 250 ms, followed by an 800-ms mask (a circle with a cross inside) and a 100-ms blank screen (presentation rate: one digit every 1150 ms). Digits were selected at random with the restriction that each digit appeared once every Stimulation. ...
Current theoretical accounts on the oscillatory nature of sustained attention predict that entrainment via transcranial alternating current stimulation (tACS) at alpha and theta frequencies on specific areas of the prefrontal cortex could prevent the drops in vigilance across time‐on‐task. Nonetheless, most previous studies have neglected both the fact that vigilance comprises two dissociable components (i.e., arousal and executive vigilance) and the potential role of differences in arousal levels. We examined the effects of theta‐ and alpha‐tACS over the right dorsolateral prefrontal cortex in both components of vigilance and in participants who differed in arousal level according to their chronotype and time of testing. Intermediate‐types performed the vigilance tasks when their arousal level was optimal, whereas evening‐types performed the vigilance tasks when their arousal levels were non‐ optimal. Both theta‐ and alpha‐tACS improved arousal vigilance in the psychomotor vigilance task (PVT), whereas alpha‐tACS, but not theta‐tACS, improved executive vigilance in the sustained attention to response task (SART), and counteracted the typical vigilance decrement usually observed in this task. Importantly, these stimulation effects were only found when arousal was low (i.e., with evening‐types performing the tasks at their non‐optimal time of day). The results support the multicomponent view of vigilance, the relevance of heeding individual differences in arousal, and the role of alpha oscillations as a long‐range cortical scale synchronization mechanism that compensates the decrements in performance as a function of time‐on‐task by exerting and maintaining cognitive control attributed to activation of the right dorsolateral prefrontal cortex.
... Fourteen subjects participated in the experiment when they were hospitalized for invasive epilepsy monitoring and subsequent seizure localization. Use of intracranial recordings of patients undergoing epilepsy monitoring to study cognitive phenomena is gaining popularity [25]- [28]. Each subject had a history of drug-resistant complex-partial seizures. ...
... C. Analysis of Networks for Specific Frequency Bands 1) Increased Theta Band Activity During Task Performance: Greater theta band activity is known to be associated with cognitive control [27], [42]- [46]. Using bandpass filtering, the neural activity in the task and non-task periods was divided into five subbands: theta (4-8 Hz), alpha (8)(9)(10)(11)(12)(13), beta (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30), gamma-1 , and gamma-2 (65-100 Hz). Relative power in the theta band was computed as a ratio of the spectral power in the 4-8 Hz frequency range to the total power spectral density in 4-100 Hz. ...
Mental disorders are a major source of disability, with few effective treatments. It has recently been argued that these diseases might be effectively treated by focusing on decision-making, and specifically remediating decision-making deficits that act as "ingredients" in these disorders. Prior work showed that direct electrical brain stimulation can enhance human cognitive control, and consequently decision-making. This raises a challenge of detecting cognitive control lapses directly from electrical brain activity. Here, we demonstrate approaches to overcome that challenge. We propose a novel method, referred to as maximal variance node merging (MVNM), that merges nodes within a brain region to construct informative inter-region brain networks. We employ this method to estimate functional (correlational) and effective (causal) networks using local field potentials (LFP) during a cognitive behavioral task. The effective networks computed using convergent cross mapping differentiate task engagement from background neural activity with 85% median classification accuracy. We also derive task engagement networks (TENs): networks that constitute the most discriminative inter-region connections. Subsequent graph analysis illustrates the crucial role of the dorsolateral prefrontal cortex (dlPFC) in task engagement, consistent with a widely accepted model for cognition. We also show that task engagement is linked to prefrontal cortex theta (4-8 Hz) oscillations. We, therefore, identify objective biomarkers associated with task engagement. These approaches may generalize to other cognitive functions, forming the basis of a network-based approach to detecting and rectifying decision deficits.
... Our results echo the findings of previous research suggesting that this connectivity provides a mechanism for increasing cognitive control following a negative outcome to efficiently regulate subsequent behaviors. Consistent with previous intracranial electrocorticography evidence (Oehrn et al., 2014;Smith et al., 2015) our directed connectivity results estimate that this information propagation stems from the MPFC. Contrary to Luft et al. (2013), we proposed that these synchrony measures are not directly correlated with the learning and option value updating mechanism. ...
Methamphetamine use disorder (MUD) as a major public health risk is associated with dysfunctional neural feedback processing. Although dysfunctional feedback processing in people who are substance dependent has been explored in several behavioral, computational, and electrocortical studies, this mechanism in MUDs requires to be well understood. Furthermore, the current understanding of latent components of their behavior such as learning speed and exploration-exploitation dilemma is still limited. In addition, the association between the latent cognitive components and the related neural mechanisms also needs to be explored. Therefore, in this study, the underlying neurocognitive mechanisms of feedback processing of such impairment, and age/gender-matched healthy controls are evaluated within a probabilistic learning task with rewards and punishments. Mathematical modeling results based on the Q-learning paradigm suggested that MUDs show less sensitivity in distinguishing optimal options. Additionally, it may be worth noting that MUDs exhibited a slight decrease in their ability to learn from negative feedback compared to healthy controls. Also through the lens of underlying neural mechanisms, MUDs showed lower theta power at the medial-frontal areas while responding to negative feedback. However, other EEG measures of reinforcement learning including feedback-related negativity, parietal-P300, and activity flow from the medial frontal to lateral prefrontal regions, remained intact in MUDs. On the other hand, the elimination of the linkage between value sensitivity and medial-frontal theta activity in MUDs was observed. The observed dysfunction could be due to the adverse effects of methamphetamine on the cortico-striatal dopamine circuit, which is reflected in the anterior cingulate cortex activity as the most likely region responsible for efficient behavior adjustment. These findings could help us to pave the way toward tailored therapeutic approaches.
... In contrast, it has also been demonstrated that a distinct theta signal in dorsomedial PFC (dmPFC) is involved in cognitive control of decision making during actions and performance monitoring 71,72 . In particular, human intracranial studies report increased theta communication between STN and dmPFC when cognitive control is needed during difficult and high conflict decisions, as well as after errors 73,75,107,108 . ...
Choosing whether to exert effort to obtain rewards is fundamental to human motivated behavior. However, the neural dynamics underlying the evaluation of reward and effort in humans is poorly understood. Here, we investigate this with chronic intracranial recordings from prefrontal cortex (PFC) and basal ganglia (BG; subthalamic nuclei and globus pallidus) in people with Parkinson's disease performing a decision-making task with offers that varied in levels of reward and physical effort required. This revealed dissociable neural signatures of reward and effort, with BG beta (12-20 Hz) oscillations tracking subjective effort on a single trial basis and PFC theta (4-7 Hz) signaling previous trial reward. Stimulation of PFC increased overall acceptance of offers in addition to increasing the impact of reward on choices. This work uncovers oscillatory mechanisms that guide fundamental decisions to exert effort for reward across BG and PFC, as well as supporting a causal role of PFC for such choices.
... Targeted regions and hemispheres varied across participants for clinical reasons and included the hippocampus in the left (n = 12) and right (n = 13) hemisphere and the entorhinal cortex in the left (n = 12) and right (n = 11) hemisphere. We selected the two most medial channels on each electrode targeting the hippocampus or the entorhinal cortex as in previous studies (Oehrn et al., 2014;Pacheco Estefan et al., 2019). The final number of selected channels in each region for each participant is listed in Table 1. ...
Working memory (WM) maintenance relies on multiple brain regions and inter-regional communications. The hippocampus and entorhinal cortex (EC) are thought to support this operation. Besides, EC is the main gateway for information between the hippocampus and neocortex. However, the circuit-level mechanism of this interaction during WM maintenance remains unclear in humans. To address these questions, we recorded the intracranial electroencephalography from the hippocampus and EC while patients ( N = 13, six females) performed WM tasks. We found that WM maintenance was accompanied by enhanced theta/alpha band (2–12 Hz) phase synchronization between the hippocampus to the EC. The Granger causality and phase slope index analyses consistently showed that WM maintenance was associated with theta/alpha band-coordinated unidirectional influence from the hippocampus to the EC. Besides, this unidirectional inter-regional communication increased with WM load and predicted WM load during memory maintenance. These findings demonstrate that WM maintenance in humans engages the hippocampal–entorhinal circuit, with the hippocampus influencing the EC in a load-dependent manner.
... For the frontoparietal network, we hypothesized an increase in information from the dorsolateral to intraparietal regions and from the intraparietal to visual cortex, reflecting initializing and enforcing the top-down cognitive control, respectively (Sarter, Givens, & Bruno, 2001). Within-network connectivity was expected to increase in theta frequency band (Oehrn et al., 2014). An increase in information flow from the frontoparietal network toward the visual cortex was expected in beta frequency bands (Spadone, Wyczesany, Della Penna, Corbetta, & Capotosto, 2021;Ligeza & Wyczesany, 2017). ...
Self-control is a core aspect of adaptive human behavior. It allows the attainment of personal goals by regulating unwanted thoughts, emotions, and behavior. Previous research highlighted the crucial role of cognitive control for explicitly pursued self-control and explicit emotion regulation strategies (such as cognitive reappraisal or attentional distraction). The present study investigated whether similar neural mechanisms would be involved in an implicit self-control task that acted as a covert emotion regulation strategy. Thirty-six female participants unscrambled sentences of either neutral (no-regulation condition) or neutral and self-control-related content (regulation condition; REG) before passively viewing negative and neutral pictures. Compared with the no-regulation condition, implicit induction of self-control reduced the amplitude of the late positive potential to negative pictures, indicating successful emotion downregulation. Crucially, implicit self-control enhanced connectivity within the two cognitive control brain networks in the theta frequency band. Specifically, for the frontoparietal network, increased connectivity from the dorsolateral PFC to the intraparietal cortex was observed. For the cingulo-opercular network, increased connectivity from dorsal anterior cingulate cortex to the left anterior insula/frontal operculum and from the right anterior insula/frontal operculum to the dorsal anterior cingulate cortex was observed. These effects were accompanied by a decrease in prestimulus alpha power in the right primary visual cortex, suggesting adjustment of attentional and perceptual processes in preparation for the upcoming affective stimulation. Together, our results indicate that self-control enhances cognitive control that is necessary for setting, maintaining, and monitoring the achievement of self-control behavior, as well as regulation of attentional and emotional processes.
... Targeted regions and hemispheres varied across participants for clinical reasons and included the hippocampus in the left (n = 13) and right (n = 14) hemispheres and the amygdala in the left (n = 13) and right (n = 11) hemispheres. We selected the two most medial channels on each electrode targeting the hippocampus or the amygdala, as was done in previous studies 26,44 . This procedure was used to minimize inter-individual variability, which would be higher if different numbers of channels would have been selected across participants. ...
Both the hippocampus and amygdala are involved in working memory (WM) processing. However, their specific role in WM is still an open question. Here, we simultaneously recorded intracranial EEG from the amygdala and hippocampus of epilepsy patients while performing a WM task, and compared their representation patterns during the encoding and maintenance periods. By combining multivariate representational analysis and connectivity analyses with machine learning methods, our results revealed a functional specialization of the amygdala-hippocampal circuit: The mnemonic representations in the amygdala were highly distinct and decreased from encoding to maintenance. The hippocampal representations, however, were more similar across different items but remained stable in the absence of the stimulus. WM encoding and maintenance were associated with bidirectional information flow between the amygdala and the hippocampus in low-frequency bands (1–40 Hz). Furthermore, the decoding accuracy on WM load was higher by using representational features in the amygdala during encoding and in the hippocampus during maintenance, and by using information flow from the amygdala during encoding and that from the hippocampus during maintenance, respectively. Taken together, our study reveals that WM processing is associated with functional specialization and interaction within the amygdala-hippocampus circuit.
... The classic Stroop paradigm can be manipulated to either diminish or enhance the degree of interference and the associated mental workload. When responding is aligned with the automatic tendency, that is demonstrated in (but not exclusively) tasks of inhibitory control, namely the Stroop task (Eschmann et al., 2018;Hanslmayr et al., 2008;Oehrn et al., 2014), Simon task (Cespón et al., 2020), and Flanker task (Cavanagh et al., 2009;Nigbur et al., 2012). In addition, frontal Theta power has been functionally associated with ERP components, such as N2 (Cavanagh & Frank, 2014;Cavanagh & Shackman, 2015) as they both appear to reflect the need for cognitive control. ...
There is conflicting evidence about how interference control in healthy adults is affected by walking as compared to standing or sitting. Although the Stroop paradigm is one of the best-studied paradigms to investigate interference control, the neurodynamics associated with the Stroop task during walking have never been studied. We investigated three Stroop tasks using variants with increasing interference levels - word-reading, ink-naming, and the switching of the two tasks, combined in a systematic dual-tasking fashion with three motor conditions - sitting, standing, and treadmill walking. Neurodynamics underlying interference control were recorded using the electroencephalogram. Worsened performance was observed for the incongruent compared to congruent trials and for the switching Stroop compared to the other two variants. The early frontocentral event-related potentials (ERPs) associated with executive functions (P2, N2) differentially signaled posture-related workloads, while the later stages of information processing indexed faster interference suppression and response selection in walking compared to static conditions. The early P2 and N2 components as well as frontocentral Theta and parietal Alpha power were sensitive to increasing workloads on the motor and cognitive systems. The distinction between the type of load (motor and cognitive) became evident only in the later posterior ERP components in which the amplitude non-uniformly reflected the relative attentional demand of a task. Our data suggest that walking might facilitate selective attention and interference control in healthy adults. Existing interpretations of ERP components recorded in stationary settings should be considered with care as they might not be directly transferable to mobile settings.
... Cognitive control involves several executive operations including cue detection, conflict resolution, switching between behavioral options or the ability to wait, all functions linked to SMA hub, and other prefrontal regions ( Watanabe et al., 2015;Herz et al., 2014;Oehrn et al., 2014;Vallesi et al., 2009;Forstmann et al., 2008;Nachev et al., 2008;Isoda & Hikosaka, 2007;Rushworth et al., 2004). Specifically, the flexible function of SMA plays a dominant role in rule and task sets (Forstmann et al., 2008(Forstmann et al., , 2010Vallesi et al., 2009;Nachev et al., 2008;Rushworth et al., 2004) and is important for contextual adaptation, motor planning, stimulus-triggered responses, or selective inhibition (Albares et al., 2014;Obeso et al., 2013;Smittenaar et al., 2013;Nachev et al., 2008). ...
Background:
The SMA is fundamental in planning voluntary movements and execution of some cognitive control operations. Specifically, the SMA has been associated to play a dominant role in controlling goal-directed actions as well as those that are highly predicted (i.e., automatic). Yet, the essential contribution of SMA in goal-directed or automatic control of behavior is scarce. Our objective was to test the possible direct role of SMA in automatic and voluntary response inhibition.
Methods:
We separately applied two noninvasive brain stimulation (NIBS) inhibitory techniques over SMA: either continuous theta-burst stimulation using repetitive transcranial magnetic stimulation or transcranial static magnetic field stimulation. Each NIBS technique was performed in a randomized, crossover, sham-controlled design. Before applying NIBS, participants practiced a go/no-go learning task where associations between stimulus and stopping behaviors were created (initiation and inhibition). After applying each NIBS, participants performed a go/no-go task with reversed associations (automatic control) and the stop signal task (voluntary control).
Results:
Learning associations between stimuli and response initiation/inhibition was achieved by participants and therefore automatized during training. However, no significant differences between real and sham NIBS were found in either automatic (go/no-go learning task) or voluntary inhibition (stop signal task), with Bayesian statistics providing moderate evidence of absence.
Conclusions:
Our results are compatible with a nondirect involvement of SMA in automatic control of behavior. Further studies are needed to prove a noncausal link between prior neuroimaging findings relative to SMA controlling functions and the observed behavior.
... Le sommeil profond, Figure 10). Dans ce modèle, la synchronisation de la phase thêta faciliterait la coordination entre le pMFC, reconnu pour être impliqué dans le contrôle exécutif tonique (cingulo-opercular system, Figure 5) et le cortex préfrontal latéral (LPFC) [173], reconnu pour être impliqué dans le contrôle exécutif phasique (fronto-parietal control system, Finalement, le couplage thêta-gamma phase-amplitude (theta-gamma coupling, TGC) refléterait l'influence à distance des aires impliquées dans le contrôle attentionnel sur l'activité corticale locale associée à la tâche [136], lors par exemple d'un besoin accru du contrôle attentionnel [174]. ...
One of the essential characteristics that differentiate animal and plant species is their ability to move in space. It thus appears that motor skills condition the development of cognition. In this respect, the present thesis begins with a triple observation, that: (1) attention is subordinated to action, (2) there is an intimate relationship between attentional control and sensorimotor control through the exercise of sustained attention, and (3) there is a second (inverse) relationship between attentional control and sensorimotor control through the exercise of stillness. Through work on brain electrophysiology in different attentional conditions - action observation, attention deficit (with or without hyperactivity), and mindfulness meditation - the present thesis aims to contribute to the identification of brain dynamics underlying attentional control and the ways in which the exercise of this control can, in turn, modulate the brain's procedural activities. After a detailed review of the fundamental properties of attention, the general principles of electroencephalogram, and the neural correlates underlying attentional control, we preliminarily focused on the oscillatory dynamics associated with visual attention. From an experimental point of view, the aim was to distinguish the different functional components (visual, attentional, sensorimotor) of the brain rhythms by modifying the visual information (an animation of walking) passively submitted to the subject's attention. On this basis, we next explored brain dynamics in children with attention deficit (with/without hyperactivity, ADHD) during an attention/inhibition task (Cue-GO/NoGO). We showed an alteration of the rhythms linked to the processing of visual information. From a neuroanatomical point of view, our data indicated that this deficit would be based on an imbalance between the two fronto-parietal attention systems, ventral-medial and dorso-lateral, which could make these children more sensitive to the salience of visual information and induce less flexibility in cognitive control. In contrast, we showed that the 'non-reactive' dimension of mindfulness altered the temporal dynamics of large-scale neural networks. This effect appeared to be support by increased cerebellum activity, and to induce less (re)activity of the attentional salience network to distractions. The theoretical and potentially clinical implications of these results are discussed, taking into account the specific scientific context of each study, the analytical tools used (event-related potentials, source location, microstates) and their limitations. In sum, our data suggest that mindfulness meditation may induce a reorganization of the cortico-subcortical loops that govern attentional behavior, and may be useful in the treatment of ADHD.
... Our results echo the finding of the previous investigation suggesting that this connectivity provide a mechanism to increase cognitive control following negative outcome to efficiently adjust subsequent behaviors. Consistent with previous intracranial electrocorticography evidence (Oehrn et al., 2014;E. H. Smith et al., 2015) our directed connectivity results estimate that this information propagation stems from the MPFC. ...
Methamphetamine use disorder associated with a dysfunctional neural feedback (reward-punishment) processing system and is considered a public health risk. Although several behavioral, computational, and electrocortical studies have explored feedback processing in other groups of individuals, the precise mechanisms of feedback processing dysfunction in methamphetamine use dependent (MUD) individuals remain unclear. Furthermore, our recent knowledge about the underlying feedback-related connectivity patterns and intertwining latent components of behavior with electrocortical signals in MUDs remained quite poor. The present study intended to fill these gaps by exploring the behavioral and electrocortical responses of abstained MUDs during a feedback-based learning paradigm. As mathematical models revealed, MUDs have less sensitivity to distinguishing optimal options (less sensitivity to options value) and learned less from negative feedback, compared with healthy controls. The MUDs also presented smaller medial-frontal theta (5-8 Hz) oscillations in response to negative feedback (300-550 ms post feedback) while other measures responsible for learning including, feedback-related negativity (FRN), parietal-P300, and a flux originated from medial frontal to lateral prefrontal remained intact for them. Further, in contrast to healthy controls, the observed association between feedback sensitivity and medial-frontal theta activity is eliminated in MUDs. We suggested that these results in MUDs may be due to the adverse effect of methamphetamine on the cortico-striatal dopamine circuit, reflected in anterior cingulate cortex (ACC) activity as the best candidate region responsible for efficient behavior adjustment. This study unveils the underlying neural mechanism of feedback processing in individuals with methamphetamine use history and could offer individual therapeutic approaches.
... Thereafter, Granger causality (2-34 Hz) was calculated based on the transfer matrices computed from the autoregressive coefficients. In order to assess statistically the directionality between the amygdala and the hippocampus, the Granger coefficients were compared using a cluster-based permutation test to quantify main effects of emotion, successful encoding and the interaction between them (eR-eKF vs. nR-nKF) in both directions (amygdala to hippocampus and hippocampus to amygdala), as described previously 16,65 . ...
Memory for aversive events is central to survival but can become maladaptive in psychiatric disorders. Memory enhancement for emotional events is thought to depend on amygdala modulation of hippocampal activity. However, the neural dynamics of amygdala-hippocampal communication during emotional memory encoding remain unknown. Using simultaneous intracranial recordings from both structures in human patients, here we show that successful emotional memory encoding depends on the amygdala theta phase to which hippocampal gamma activity and neuronal firing couple. The phase difference between subsequently remembered vs. not-remembered emotional stimuli translates to a time period that enables lagged coherence between amygdala and downstream hippocampal gamma. These results reveal a mechanism whereby amygdala theta phase coordinates transient amygdala -hippocampal gamma coherence to facilitate aversive memory encoding. Pacing of lagged gamma coherence via amygdala theta phase may represent a general mechanism through which the amygdala relays emotional content to distant brain regions to modulate other aspects of cognition, such as attention and decision-making.
... Consistently, EEG and magnetoencephalography (MEG) studies have linked power changes in prefrontal theta activity to a temporal reorganization of neural networks coinciding with decision points, i.e., action monitoring and selection (Cavanagh et al., 2012). Similarly, a considerable amount of work has found midfrontal theta power and phase synchronization in frontal regions (ACC and PFC) associated with stimulus conflict detection and response monitoring (Brunetti et al., 2019;Cavanagh & Frank, 2014;Duprez et al., 2018;Oehrn et al., 2014;Pastötter et al., 2013;Pscherer et al., 2021). Although frontal theta appears to be the optimal candidate for regulating and modulating executive control functions, it is not the only one. ...
... Targeted regions and hemispheres varied across participants for clinical reasons and included the hippocampus in the left (n = 12) and right (n = 13) hemispheres and the entorhinal cortex in the left (n = 12) and right (n = 11) hemispheres. We selected the two most medial channels on each electrode targeting the hippocampus or the entorhinal cortex, as was done in previous studies(52,53). This procedure was used to minimize interindividual variability, which would be higher if different numbers of channels had been selected across participants. ...
Working memory (WM) is the ability to actively maintain information for a short time and is central to human behavior. Rodent studies have proposed that hippocampal-entorhinal communication supports WM maintenance. However, the exact neural mechanisms of this interaction in WM remains unclear in humans. To address these questions, we combined machine learning analyses with intracranial electroencephalography (iEEG) recordings from the hippocampus and the entorhinal cortex (EC) in human participants, who maintained a set of letters in their WM. We found that WM maintenance was accompanied by elevated bidirectional hippocampal-EC information exchange via the theta band (2–8 Hz) and bidirectional cross-region theta-gamma phase-amplitude coupling (PAC). Further decoding analyses showed that the unidirectional inter-regional communication, with both theta oscillations in the hippocampus modulating EC gamma activity and theta band-coordinated information flow from the hippocampus, could decode correct performance at the level of participants. Taken together, our results demonstrate that theta functional coupling in the hippocampal-EC supports the maintenance of WM information via a specific pattern of frequency and direction. This connectivity-based coding could shed light on the neural mechanisms of WM processing.
Significance
Recent studies suggest a role for the hippocampus in working memory. How does the hippocampus coordinate with other brain regions to retain working memory information? The entorhinal cortex (EC) is the main gateway for information between the hippocampus and neocortex. To delineate whether (and how) the hippocampus and the entorhinal cortex interact during working memory and whether such interaction supports successful working memory, we used machine learning analyses of human intracranial EEG recordings while patients performed working memory tasks. Our results suggest that the human hippocampal-EC circuit supports working memory and is maintained in specific connectivity patterns, with a theta band (2–8 Hz)-coordinated unidirectional influence from the hippocampus to the EC. Our findings reveal that dynamic unidirectional interactions within the hippocampal-EC circuit underlie working memory and can contribute to a mechanistic circuit understanding of working memory.
... Each and right (n = 11) hemispheres. We selected the two most medial channels on each electrode targeting the hippocampus or the amygdala, as was done in previous studies 27,43 . This procedure was used to minimize inter-individual variability, which would be higher if different numbers of channels would have been selected across subjects. ...
Both the hippocampus and amygdala are involved in working memory (WM) processing. However, it is still an open question how the two structures interact to represent and maintain WM content. Here, we simultaneously recorded intracranial EEG from the amygdala and hippocampus of epilepsy patients while performing a WM task. Using a series of univariate, multivariate, and connectivity analyses, our results revealed a functional specialization of the amygdala-hippocampus circuit: The mnemonic representations in the amygdala were highly distinct and decreased from encoding to maintenance. The hippocampal representations, however, were less specific but remained stable in the absence of the stimulus. Furthermore, the amygdala and hippocampus coordinated their activity during WM: The hippocampal representation was reinstated in the amygdala during maintenance, with task induced information flow from the hippocampus to the amygdala. Importantly, the functional specificity and coordination were correlated only when they appeared in correct trials. Our study provides new evidence that successful WM processing in humans is associated with specialized and coordinated functions within the amygdala-hippocampus circuit.
... Consistently, EEG and magnetoencephalography (MEG) studies have linked power changes in prefrontal theta activity to temporal reorganization of neural networks coinciding with decision points, i.e., action monitoring and selection (Cavanagh et al., 2012). Similarly, a considerable amount of work has found midfrontal theta power and phase synchronization in frontal electrode clusters (ACC and PFC) associated with stimulus conflict detection and response monitoring (Pastötter et al., 2013;Cavanagh and Frank, 2014;Oehrn et al., 2014;Duprez et al., 2018;Brunetti et al., 2019;Pscherer et al., 2021). ...
The present study uses EEG time-frequency representations (TFRs) with a Flanker task to investigate if and how individual differences in bilingual language experience modulate neurocognitive outcomes (oscillatory dynamics) in two bilingual group types: late bilinguals (L2 learners) and early bilinguals (heritage speakers—HSs). TFRs were computed for both incongruent and congruent trials. The difference between the two (Flanker effect vis-à-vis cognitive interference) was then (1) compared between the HSs and the L2 learners, (2) modeled as a function of individual differences with bilingual experience within each group separately and (3) probed for its potential (a)symmetry between brain and behavioral data. We found no differences at the behavioral and neural levels for the between-groups comparisons. However, oscillatory dynamics (mainly theta increase and alpha suppression) of inhibition and cognitive control were found to be modulated by individual differences in bilingual language experience, albeit distinctly within each bilingual group. While the results indicate adaptations toward differential brain recruitment in line with bilingual language experience variation overall, this does not manifest uniformly. Rather, earlier versus later onset to bilingualism—the bilingual type—seems to constitute an independent qualifier to how individual differences play out.
... Coherent FPs can facilitate the transfer of information across shorter and longer distances Rodriguez et al., 1999;Varela et al., 2001;Fries, 2005;Liebe et al., 2012;Helfrich and Knight, 2016). Neuronal coherence has been shown to support higher-order cognitive processes Rodriguez et al., 1999;Varela et al., 2001;Benchenane et al., 2010;Oehrn et al., 2014;Fries, 2015). Therefore, measuring the spatial reach of coherence is an important step toward understanding the nature of rhythmic information flow across the brain. ...
Neuronal coherence is thought to be a fundamental mechanism of communication in the brain, where synchronized field potentials coordinate synaptic and spiking events to support plasticity and learning. Although the spread of field potentials has garnered great interest, little is known about the spatial reach of phase synchronization, or neuronal coherence. Functional connectivity between different brain regions is known to occur across long distances, but the locality of synchronization across the neocortex is understudied. Here we used simultaneous recordings from electrocorticography (ECoG) grids and high-density microelectrode arrays to estimate the spatial reach of neuronal coherence and spike-field coherence (SFC) across frontal, temporal, and occipital cortices during cognitive tasks in humans. We observed the strongest coherence within a 2-3 cm distance from the microelectrode arrays, potentially defining an effective range for local communication. This range was relatively consistent across brain regions, spectral frequencies, and cognitive tasks. The magnitude of coherence showed power law decay with increasing distance from the microelectrode arrays, where the highest coherence occurred between ECoG contacts, followed by coherence between ECoG and deep cortical LFP, and then SFC (i.e., ECoG > LFP > SFC). The spectral frequency of coherence also affected its magnitude. Alpha coherence (8-14 Hz) was generally higher than other frequencies for signals nearest the microelectrode arrays, whereas delta coherence (1-3 Hz) was higher for signals that were farther away. Action potentials in all brain regions were most coherent with the phase of alpha oscillations, which suggests that alpha waves could play a larger, more spatially local role in spike timing than other frequencies. These findings provide a deeper understanding of the spatial and spectral dynamics of neuronal synchronization, further advancing knowledge about how activity propagates across the human brain.SIGNIFICANCE STATEMENTCoherence is theorized to facilitate information transfer across cerebral space by providing a convenient electrophysiological mechanism to modulate membrane potentials in spatiotemporally complex patterns. Our work uses a multi-scale approach to evaluate the spatial reach of phase coherence and spike-field coherence during cognitive tasks in humans. Locally, coherence can reach up to 3 cm around a given area of neocortex. The spectral properties of coherence revealed that alpha phase- and spike-field coherence were higher within ranges less than 2 cm, whereas lower frequency delta coherence was higher for contacts farther away. Spatiotemporally shared information (i.e., coherence) across neocortex seems to reach farther than field potentials alone.
... Conflict resolution is a classic example of cognitive control in which the brain dynamically adapts to the changing environment and directs attention to the task-relevant stimuli (Egner and Hirsch, 2005). Studies on humans and non-humans primates have indicated that dACC located in the MPC and DLPFC play a crucial role in conflict detection and conflict resolution (Botvinick et al., 1999;Egner and Hirsch, 2005;Oehrn et al., 2014). NIBS methods have emerged as potential neuromodulatory tools to understand the functioning of specific brain regions involved in complex cognitive processes such as interference control (Hsu et al., 2015). ...
Medial prefrontal cortex (MPC) has been associated with a wide range of cognitive functions; however, its specific role in interference control is not fully understood. The current study investigates the role of MPC in interference control by externally stimulating it with an electric current and studying associated behavioral and neurophysiological markers. Participants randomly assigned to experimental and sham groups were administered with a high-definition transcranial direct current stimulation (HD-tDCS) of 2mA for 15 minutes. They performed a classic color-word Stroop task before, during, and immediately after the stimulation, while electroencephalography (EEG) was acquired throughout the experiment. A decrease in reaction time (RT) for incongruent and neutral trials of the Stroop task was observed in the experimental group compared to the sham group with a significant reduction in the Stroop Effect after stimulation; however, no significant change was observed in the amplitude and latency of N200, P200, and N450 event related potentials. Furthermore, the resting state complexity of the neural signals in the medial frontal region was decreased in the experimental group with a decrease in theta frequency band during the Stroop task. We conclude that the stimulation of MPC increases its efficiency in resolving the conflict by reducing theta power during the Stroop task, which is also reflected in the reduced complexity in the resting state EEG. (ClinicalTrials.gov Identifier: NCT04318522)
... Targeted regions and hemispheres varied across subjects for clinical reasons and included the hippocampus in the left (n = 13) and right (n = 14) hemispheres and the amygdala in the left (n = 13) and right (n = 11) hemispheres. We selected the two most medial channels on each electrode targeting the hippocampus or the amygdala, as was done in previous studies 27,43 . This procedure was used to minimize inter-individual variability, which would be higher if different numbers of channels would have been selected across subjects. ...
Both the hippocampus and amygdala are involved in working memory (WM) processing. However, it is still an open question how the two structures interact to represent and maintain WM content. Here, we simultaneously recorded intracranial EEG from the amygdala and hippocampus of epilepsy patients while performing a WM task. Using a series of univariate, multivariate, and connectivity analyses, our results revealed a functional specialization of the amygdala-hippocampus circuit: The mnemonic representations in the amygdala were highly distinct but decreased from encoding to maintenance. The hippocampal representations, however, were less specific but remained stable in the absence of stimulus. Furthermore, the amygdala and hippocampus coordinated their activity during WM: The hippocampal representation was reinstated in the amygdala during maintenance, with task induced low-frequency information flow from the hippocampus to the amygdala. Importantly, the functional specificity and coordination were correlated only when they appeared in correct trials. Our study provides new evidence that successful WM processing in humans relies on specialized and coordinated functions within the amygdala-hippocampus circuit.
... Nevertheless, the finding that these regional activations in orienting attention were negatively correlated with age suggests that these two attentional networks, which were functionally undifferentiated in childhood, may have differentiated during development, thereby decreasing the involvement of executive processes for orienting attention. Although the IFG is involved in attention reallocation triggered by external stimuli, 20 DMPFC is involved in error detection and conflict resolution, 21,22 It is interesting to determine the relationship between these suggested age-related transformations in brain function and the development of brain structure in childhood and adolescence. Although it is well known that gray matter volume gradually decreases from childhood through adolescence and into adulthood, 24,25 no clear findings have been made on whether task-induced regional brain function correlates with gray matter volume. ...
Attention ability is one of the most important cognitive functions. It develops mainly during school age. However, the neural basis for the typical development of attentional functions has not been fully investigated. To clarify the development of the aforementioned function and its neural basis, this study examined brain function in children and adolescents during the performance of an attention network test (ANT) using functional magnetic resonance imaging. One hundred and sixty-three volunteers (8-23 years, 80 female) participated in this study. Using a modified version of ANT, we assessed the efficiency of two attentional functions-orienting and executive attention-by measuring how reaction time is affected by spatial cue location and flanker congruency and examined the functional brain areas-attentional networks-associated with two attentional functions. Consistent with the findings of previous studies, the superior parietal lobule, visual association cortex, left precentral gyrus, and supplementary motor area were activated during the orienting attention, while the anterior cingulate cortex, visual association cortex, lateral prefrontal cortex, thalamus, and caudate were activated during the executive attention. Moreover, negative correlations with age were found for activations in the inferior frontal gyrus, dorsomedial prefrontal cortex, and caudate nucleus in the orienting attention, while no correlations with age related to executive attention were found. In conclusion, this study revealed common and distinct features in the neural basis of the attentional functions in children and adolescents compared with that of adults and their developmental changes with age.
... For conflict response, the Stroop task requires participants to suppress automatic responses to incongruent stimuli until processing is complete (i.e. patients must suppress the automatic response 'blue' after seeing the word 'BLUE' printed in the color red) [77]. Previous studies suggest that the hippocampus plays a role in successful conflict processing because patients suffering from hippocampal sclerosis perform worse than healthy control groups in an auditory Stroop task [22,23], though propagation patterns in hippocampal sclerosis patients may limit interpretation [24]. ...
Introduction The human orbitofrontal cortex (OFC) is involved in automatic response inhibition and conflict processing, but the mechanism of frequency-specific power changes that control these functions is unknown. Theta and gamma activity have been independently observed in the OFC during conflict processing, while theta-gamma interactions in other brain areas have been noted primarily in studies of memory. Within the OFC, it is possible that theta-gamma phase amplitude coupling (PAC) drives conflict processing. Objective This study aims to characterize the coupled relationship between theta and gamma frequency bands in the OFC during conflict processing using a modified Stroop task. Methods Eight epilepsy patients implanted with OFC stereotactic electroencephalography (SEEG) electrodes participated in a color-word modified Stroop task. PAC between theta phase and gamma amplitude was assessed to determine the timing and magnitude of neural oscillatory changes. Group analysis was conducted using a non-parametric cluster-permutation t-test on coherence values. Results Theta-low gamma (LG) PAC significantly increased in five out of eight patients during successful trials of the incongruent condition compared with the congruent condition. Significant increases in theta-LG PAC were most prominent during cue processing 200-800ms after cue presentation. On group analysis, trial-averaged mean theta-LG PAC was statistically significantly greater in the incongruent condition compared to the congruent condition (p < 0.001, Cohen’s d=0.51). Conclusion For the first time, we report that OFC theta phase and LG amplitude coupling increases during conflict resolution. Given the delayed onset after cue presentation, OFC theta-LG PAC may contribute to conflict processing after conflict detection and before motor response. This explanation follows the hypothesis that global theta waves modulate local gamma signals. Understanding this relationship within the OFC will help further elucidate the neural mechanisms of human conflict resolution.
... Generally, the dACC plays an essential role in monitoring cognitive control by adjusting automatic behavioral patterns to meet specific task demands (Botvinick et al., 2001;Shenhav et al., 2013;Ullsperger et al., 2014). In more detail, dACC activation is associated with occurring conflicts between control signals (Botvinick et al., 2001;Oehrn et al., 2014;Sheth et al., 2012;Tang et al., 2016), error monitoring (Heilbronner & Hayden, 2016;Ito et al., 2003;Shen et al., 2015) and negative feedback (Amiez et al., 2012). Inhibitory transcranial direct current stimulation of the dACC leads to decreased neuronal responses following errors and negative feedback, which subsequently results in poorer accuracy and reduced learning . ...
The neurobiological basis of learning is reflected in adaptations of brain structure, network organization and energy metabolism. However, it is still unknown how different neuroplastic mechanisms act together and if cognitive advancements relate to general or task-specific changes. To address these questions, we tested how hierarchical network interactions contribute to improvements in the performance of a visuo-spatial processing task by employing simultaneous PET/MR neuroimaging before and after a 4-week learning period. We combined functional PET with metabolic connectivity mapping (MCM) to infer directional interactions across brain regions and subsequently performed simulations to disentangle the role of functional network dynamics and glucose metabolism. As a result, learning altered the top-down regulation of the salience network onto the occipital cortex, with increases in MCM at resting-state and decreases during task execution. Accordingly, a higher divergence between resting-state and task-specific effects was associated with better cognitive performance, indicating that these adaptations are complementary and both required for successful skill learning. Simulations further showed that changes at resting-state were dependent on glucose metabolism, whereas those during task performance were driven by functional connectivity between salience and visual networks. Referring to previous work, we suggest that learning establishes a metabolically expensive skill engram at rest, whose retrieval serves for efficient task execution by minimizing prediction errors between neuronal representations of brain regions on different hierarchical levels.
... On the other hand, our results observe comparatively more connectivity of dmPFC for less-familiar contexts. Activity in the dmPFC is mostly reported in resolving valence & emotional conflicts [28,21,13,39] and in dynamic adaptation to stimulus-response values [36,15]. ...
Emotion experiments with naturalistic paradigms are emerging and giving new insights into dynamic brain activity. Context familiarity is considered as an important dimensions of emotion processing by appraisal theorists. However, how the context un/familiarity of the naturalistic stimuli influences the central and autonomic activity is not probed yet [check it]. Hence, we tried to address this issue in this work by breaking it down into three questions. 1) What is the relation between context un/familiarity with the neural correlates of self-assessment affective dimensions viz. valence and arousal; 2) the influence of context un/familiarity in cardiac-brain mutual interaction during emotion processing; 3.) brain network reorganization to accommodate the degree of context familiarity. We found that the less-context familiarity is primarily attributed to negative emotion feeling mediated by lack of predictability of sensory experience. Whereas, with high-context familiarity, both positive and negative emotions are felt. For less-context familiarity, the arousal activity is negatively correlated with EEG power. In addition, the cardiac activity for both high and less context familiarity is modulated before the reported self-awareness of emotional feeling. The correlation of cortical regions with cardiac activity and connectivity patterns reveals that ECG is modulated by salient feature during pre-awareness and correlates with AIC and conceptual hub in high-familiarity. Whereas, for the low familiarity, the cardiac activity is correlated with the exteroceptive sensory regions. In addition, we found that OFC and dmPFC have high connectivity with less-context familiarity, whereas AIC has high connectivity with high-context familiarity. To the best of our knowledge, the context familiarity and its influence on cardiac and brain activity have never been reported with a naturalistic paradigm. Hence, this study significantly contributes to understanding automatic processing of emotions by analyzing the effect of context un/familiarity on affective feelings, the dynamics of cardiac-brain mutual interaction, and the brain's effective connectivity during pre-awareness.
... This technique has been proven to boost cognitive performance by enhancing the transfer of information among anatomically and functionally connected brain areas, which improve cognitive processes when the current is applied at speci c oscillatory frequencies that concur with the endogenous regional synchronization involved in such cognitive functions. Both theta and alpha activity within the frontoparietal control network have been associated with either an increase or a decrease of cognitive control that are thought to be crucial for vigilance [29][30][31][32][33][34][35][36][37][38][39][40]. Congruently, and in accordance with the oscillatory models of sustained attention [20,28], previous tACS studies on sustained attention stimulated at these two frequencies. ...
Background
Current theoretical accounts on the oscillatory nature of sustained attention predict that entrainment via transcranial alternating current stimulation (tACS) at alpha and theta frequencies on the frontoparietal network could prevent the drops in vigilance across time-on-task. Nonetheless, most previous studies have neglected both the fact that vigilance comprises two dissociable components (i.e. arousal and executive vigilance) and the potential role of differences in arousal baseline.
Method
We examined the effects of theta- and alpha-tACS over the right dorsolateral prefrontal cortex on both components of vigilance and on participants that differed in arousal baseline according to their chronotype and the time of testing. Intermediate-types performed the vigilance tasks when their arousal baseline was at the optimal level, whereas evening-types performed the vigilance tasks when their arousal baseline was at non-optimal levels.
Results
Both theta- and alpha-tACS improved arousal vigilance, whereas alpha-tACS, but not theta-tACS, improved accuracy and attenuated the typical vigilance decrement in the executive vigilance task. Importantly, these stimulation effects were only found when arousal baseline was low (i.e., with evening-types performing the tasks at their non-optimal time of day).
Conclusion
The results support the multicomponent view of vigilance, the relevance of heeding individual differences in arousal baseline, and the role of alpha oscillations as a long-range cortical scale synchronization mechanism that compensates the decrements in performance as a function of time-on-task by exerting and maintaining cognitive control attributed to activation of the frontoparietal network.
... On the other hand, theta phase synchronization allows theta-driven cognitive monitoring systems to exert control over attention via connecting the pMFC and LPFC [6]. For example, theta phase synchronization between pMFC and LPFC increased significantly during high response conflicts [9] or following negative feedback [8], both demanding an effective transmission of information between these two brain areas. However, regardless of fm-theta power, pMFC-LPFC theta phase synchronization, or other oscillatory features, whether they are merely correlated or have causal relationships with sustained attention remains unknown. ...
Theta oscillations over the posterior medial frontal cortex (pMFC) and lateral prefrontal cortex (LPFC) play vital roles in sustained attention. Specifically, pMFC power and pMFC-LPFC synchronization correlate with cognitive control in sustained-attention-related tasks, but the causal relationships remain unknown. In the present study, we first analyzed the correlation between EEG theta oscillations (characterized by time-frequency power and phase-based connectivity) and the level of sustained attention (Experiment 1) and then utilized transcranial alternating current stimulation (tACS) to modulate theta oscillations and in turn observed its effects on sustained attention (Experiment 2). In Experiment 1, two time-frequency regions of interest (ROIs) were determined, in which high/low time-frequency power and high/low phase-based connectivity corresponded to high/low-level sustained attention. In Experiment 2, time-frequency power and phase-based connectivity of theta oscillations were compared between the sham and tACS groups within the time-frequency ROIs determined in Experiment 1. Results showed that phase-based connectivity between pMFC and LPFC significantly decreased in the tACS group compared with the sham group during the first five minutes of the poststimulation period. Moreover, a marginal trend existed that sustained attention was downregulated by tACS in the same time interval, suggesting that theta phase synchronization between pMFC and LPFC may play a causal role in sustained attention.
... As a further function, the DLPFC is involved in conflict management regarding conflict detection, resolution, and adaptation (Oehrn et al., 2014). As indicated by intracranial recordings in neurosurgical patients, conflict management in decision tasks seems to involve temporally coded mechanisms between dorsal ACC and the DLPFC (Smith et al., 2019). ...
This review article summarizes various functions of the dorsolateral prefrontal cortex (DLPFC) that are related to language processing. To this end, its connectivity with the left-dominant perisylvian language network was considered, as well as its interaction with other functional networks that, directly or indirectly, contribute to language processing. Language-related functions of the DLPFC comprise various aspects of pragmatic processing such as discourse management, integration of prosody, interpretation of nonliteral meanings, inference making, ambiguity resolution, and error repair. Neurophysiologically, the DLPFC seems to be a key region for implementing functional connectivity between the language network and other functional networks, including cortico-cortical as well as subcortical circuits. Considering clinical aspects, damage to the DLPFC causes psychiatric communication deficits rather than typical aphasic language syndromes. Although the number of well-controlled studies on DLPFC language functions is still limited, the DLPFC might be an important target region for the treatment of pragmatic language disorders.
Adapting our behavior to environmental demands relies on our capacity to perceive and manage potential conflicts within our surroundings. While evidence implicates the involvement of the lateral prefrontal cortex and theta oscillations in detecting conflict stimuli, their roles in conflict expectation remain elusive. Consequently, the exact computations and neural mechanisms underlying these cognitive processes still need to be determined. To address this gap, we employed an integrative approach involving cognitive computational modeling, fMRI, TMS, and EEG. Our results revealed a computational process underlying conflict expectation, which correlated with activity in the superior frontal gyrus (SFG). Furthermore, rhythmic TMS in the theta range applied over the SFG, but not over the inferior frontal junction, induced endogenous theta activity, enhancing computations associated with conflict expectation. These findings provide compelling evidence for the causal involvement of SFG theta activity in learning and allocating cognitive resources to address forthcoming conflict stimuli.
Significant Statement
Alterations in the processing of expectations of conflict events have been associated with several neuropsychiatric disorders that significantly affect the quality of life for many individuals. This article describes a cognitive computation underlying the conflict expectation and its causal neural mechanism involving theta brain activity in the superior frontal gyrus (SFG). Thus, unraveling this mechanism holds promise for developing interventions to address cognitive alterations related to anticipation of conflict events in neuropsychiatric disorders, improving overall cognitive function and quality of life.
The Stroop Task is a well-known neuropsychological task developed to investigate conflict processing in the human brain. Our group has utilized direct intracranial neural recordings in various brain regions during performance of a modified color-word Stroop Task to gain a mechanistic understanding of non-emotional human conflict processing. The purpose of this review article is to: 1) synthesize our own studies into a model of human conflict processing, 2) review the current literature on the Stroop Task and other conflict tasks to put our research in context, and 3) describe how these studies define a network in conflict processing. The figures presented are reprinted from our prior publications and key publications referenced in the manuscript. We summarize all studies to date that employ invasive intracranial recordings in humans during performance of conflict-inducing tasks. For our own studies, we analyzed local field potentials (LFPs) from patients with implanted stereotactic electroencephalography (SEEG) electrodes, and we observed intracortical oscillation patterns as well as intercortical temporal relationships in the hippocampus, amygdala, and orbitofrontal cortex (OFC) during the cue-processing phase of a modified Stroop Task. Our findings suggest that non-emotional human conflict processing involves modulation across multiple frequency bands within and between brain structures.
Human invasive neural recordings stem from neurological and psychiatric patients with depth and subdural electrodes implanted for diagnostic or therapeutic purposes. Electrode placement is therefore dictated by clinical needs, and the sparseness in brain coverage and variability in electrode location across patients impedes group-level analyses using random-effects models. This chapter discusses the process of electrode selection for subsequent analyses and in particular the advantages and disadvantages of two approaches. First, one can select regions-of-interest (ROIs) guided by a priori hypotheses emerging from previous findings, e.g., non-invasive lines of research. This procedure allows for random-effects analyses and inferences about the population but can lead to a loss of spatial precision and an increase of type-II error. Alternatively, one can conduct whole-brain analyses and study all available electrodes, either for each individual or across patients by means of functional pre-selection of contacts or a fixed-effects analysis with pooled data across patients. This approach preserves anatomical precision but reduces the generalizability of the findings and requires rigorous correction for type-I error. Finally, I describe one procedure that combines the strengths of ROI selection and the analysis of all electrodes and thereby represents a good compromise between the two methods.
Midfrontal theta (FMθ) in the human EEG is commonly viewed as a generic and homogeneous mechanism of cognitive control in general and conflict processing in particular. However, the role of FMθ in approach-avoidance conflicts and its cross-task relationship to simpler stimulus-response conflicts remain to be examined more closely. Therefore, we recorded EEG data while 59 healthy participants (49 female, 10 male) completed both, an approach-avoidance task and a Flanker task. Participants showed significant increases in FMθ power in response to conflicts in both tasks. To our knowledge, this is the first study to show a direct relationship between FMθ and approach-avoidance conflicts. Crucially, FMθ activity was task dependent and showed no cross-task correlation. To assess the possibility of multiple FMθ sources, we applied source separation (Generalized Eigendecomposition; GED) to distinguish independent FMθ generators. The component’s activity showed a similar pattern and was again task-specific. However, our results did not yield a clear differentiation between task-specific FMθ sources for each of the participants. Overall, our results show FMθ increases in approach avoidance conflicts, as has been established only for more simple response conflict paradigms so far. The independence of task-specific FMθ increases suggests differential sensitivity of FMθ to different forms of behavioral conflict.
The neurobiological basis of learning is reflected in adaptations of brain structure, network organization and energy metabolism. However, it is still unknown how different neuroplastic mechanisms act together and if cognitive advancements relate to general or task-specific changes. Therefore, we tested how hierarchical network interactions contribute to improvements in the performance of a visuo-spatial processing task by employing simultaneous PET/MR neuroimaging before and after a 4-week learning period. We combined functional PET and metabolic connectivity mapping (MCM) to infer directional interactions across brain regions. Learning altered the top-down regulation of the salience network onto the occipital cortex, with increases in MCM at resting-state and decreases during task execution. Accordingly, a higher divergence between resting-state and task-specific effects was associated with better cognitive performance, indicating that these adaptations are complementary and both required for successful visuo-spatial skill learning. Simulations further showed that changes at resting-state were dependent on glucose metabolism, whereas those during task performance were driven by functional connectivity between salience and visual networks. Referring to previous work, we suggest that learning establishes a metabolically expensive skill engram at rest, whose retrieval serves for efficient task execution by minimizing prediction errors between neuronal representations of brain regions on different hierarchical levels.
Although hemispheric lateralization of creativity has been a longstanding topic of debate, the underlying neurocognitive mechanism remains poorly understood. Here we designed two types of novel stimuli—novel useful and novel useless, adapted from ‘familiar useful’ designs taken from daily life—to demonstrate how the left and right medial temporal lobe (MTL) respond to novel designs of different usefulness. Taking the familiar useful design as a baseline, we found that the right MTL showed increased activation in response to novel useful designs, followed by novel useless ones, while the left MTL only showed increased activation in response to novel useful designs. Calculating an asymmetry index (AI) suggests that usefulness processing is predominant in the left MTL, whereas the right MTL is predominantly involved in novelty processing. Moreover, the left parahippocampal gyrus (PHG) showed stronger functional connectivity with the anterior cingulate cortex (ACC) when responding to novel useless designs. In contrast, the right PHG showed stronger connectivity with the amygdala, midbrain, and hippocampus. Critically, multivoxel representational similarity analyses revealed that the left MTL was more effective than the right MTL at distinguishing the usefulness differences in novel stimuli, while representational patterns in the left PHG positively predicted the post-behavior evaluation of ‘truly creative’ products. These findings suggest an apparent dissociation of the left and right MTL in integrating the novelty and usefulness information and novel associative processing during creativity evaluation, respectively. Our results provide novel insights into a longstanding and controversial question in creativity research by demonstrating functional lateralization of the MTL in processing novel associations.
Neuronal coherence is thought to be a fundamental mechanism of communication in the brain, where synchronized field potentials coordinate synaptic and spiking events to support plasticity and learning. Although the spread of field potentials has garnered great interest, little is known about the spatial reach of phase synchronization, or neuronal coherence. Functional connectivity between different brain regions is known to occur across long distances, but the locality of coherence within a brain region is understudied. Here we used simultaneous recordings from electrocorticography (ECoG) grids and high-density microelectrode arrays to estimate the spatial reach of neuronal coherence and spike-field coherence (SFC) across frontal, temporal, and occipital cortices during cognitive tasks in humans. We observed the strongest coherence within a 2-3 cm distance from the microelectrode arrays, potentially defining an effective range for local communication. This range was relatively consistent across brain regions, spectral frequencies, and cognitive tasks. The magnitude of coherence showed power law decay with increasing distance from the microelectrode arrays, where the highest coherence occurred between ECoG contacts, followed by coherence between ECoG and deep cortical LFP, and then SFC (i.e., ECoG > LFP > SFC). The spectral frequency of coherence also affected its magnitude. Alpha coherence (8-14 Hz) was generally higher than other frequencies for signals nearest the microelectrode arrays, whereas delta coherence (1-3 Hz) was higher for signals that were farther away. Action potentials in all brain regions were most coherent with the phase of alpha oscillations, which suggests that alpha waves could play a larger, more spatially local role in spike timing than other frequencies. These findings provide a deeper understanding of the spatial and spectral dynamics of neuronal coherence, further advancing knowledge about how activity propagates across the human brain.
Medial frontal theta-band oscillations are a robust marker of action-outcome monitoring. In a large developmental sample (n=432, 9-16 years), we examined whether phase and non-phase locked medial frontal theta power were related to inhibitory control among children and adolescents. Our results showed that the well-established increase in medial frontal theta power during inhibitory control was captured largely by non-phase locked dynamics, which partially mediated the positive effect of age on task performance. A person-centered approach also revealed latent classes of individuals based on their multivariate theta power dynamics (phase locked/non-phase locked, GO/NOGO). The class of individuals showing low phase locked and high non-phase locked medial frontal theta were significantly older, had better inhibitory control, scored higher on measures of general cognitive function, and were more efficient in their behavioural responses. The functional significance of phase and non-phase locked theta dynamics, and their potential changes, could have important implications for action-outcome monitoring and cognitive function in both typical and atypical development, as well as related psychopathology.
Memory for aversive events is central to survival, but can also become maladaptive in psychiatric disorders. Emotional memory relies on the amygdala and hippocampus, but the neural dynamics of their communication during emotional memory encoding remain unknown. Using simultaneous intracranial recordings from both structures in human patients, we show that in response to emotionally aversive, but not neutral, visual stimuli, the amygdala transmits unidirectional influence on the hippocampus through theta oscillations. Critically, successful emotional memory encoding depends on the precise amygdala theta phase to which hippocampal gamma activity and neuronal firing couple. The phase difference between subsequently remembered vs. not-remembered emotional stimuli translates to ~25-45 milliseconds, a time period that enables lagged coherence between amygdala and downstream hippocampal gamma activity. These results reveal a mechanism whereby amygdala theta phase coordinates transient coherence between amygdala and hippocampal gamma activity to facilitate the encoding of aversive memories in humans.
The ability to perform motor actions depends, in part, on the brain's initial state, that is the ensemble firing rate pattern prior to the initiation of action. We hypothesized that the same principle would apply to cognitive functions as well. To test this idea, we examined a unique set of single unit data collected in human dorsolateral prefrontal cortex (dlPFC). Data were collected in a conflict task that interleaves Simon (motor-type) and Eriksen (flanker-type) conflict trials. Variability in pre-trial firing rate predicted the ability to resolve conflict, as inferred from reaction times. Ensemble patterns that predicted faster Simon reaction times overlapped slightly with those predicting Eriksen performance, indicating that the two conflict types are associated with near-orthogonal initial states, and suggesting that there is a weak abstract or amodal conflict preparatory state in this region. These codes became fully orthogonalized in the response state. We interpret these results in light of the initial state and dual-mechanisms of control hypotheses, arguing that the firing patterns in dlPFC immediately preceding the start of the task predispose it for the efficient implementation of cognitive action.
(
This reprinted article originally appeared in the Journal of Experimental Psychology,
1935, Vol 18, 643–662. The following abstract of the original article appeared in PA, Vol 10:1863.) In this study pairs of conflicting stimuli, both being inherent aspects of the same symbols, were presented simultaneously (a name of one color printed in the ink of another color—a word stimulus and a color stimulus). The difference in time for reading the words printed in colors and the same words printed in black is the measure of the interference of color stimuli on reading words. The difference in the time for naming the colors in which the words are printed and the same colors printed in squares is the measure of the interference of conflicting word stimuli on naming colors. The interference of conflicting color stimuli on the time for reading 100 words (each word naming a color unlike the ink-color of its print) caused an increase of 2.3 sec or 5.6% over the normal time for reading the same words printed in black. This increase is not reliable, but the interference of conflicting word stimuli on the time for naming 100 colors (each color being the print of a word which names another color) caused an increase of 47.0 sec or 74.3% of the normal time for naming colors printed in squares.… (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Preparing to stop an inappropriate action requires keeping in mind the task goal and using this to influence the action control system. We tested the hypothesis that different subregions of prefrontal cortex show different temporal profiles consistent with dissociable contributions to preparing-to-stop, with dorsolateral prefrontal cortex (DLPFC) representing the task goal and ventrolateral prefrontal cortex (VLPFC) implementing action control. Five human subjects were studied using electrocorticography recorded from subdural grids over right lateral frontal cortex. On each trial, a task cue instructed the subject whether stopping might be needed or not (Maybe Stop [MS] or No Stop [NS]), followed by a go cue, and on some MS trials, a subsequent stop signal. We focused on go trials, comparing MS with NS. In the DLPFC, most subjects had an increase in high gamma activity following the task cue and the go cue. In contrast, in the VLPFC, all subjects had activity after the go cue near the time of the motor response on MS trials, related to behavioral slowing, and significantly later than the DLPFC activity. These different temporal profiles suggest that DLPFC and VLPFC could have dissociable roles, with DLPFC representing task goals and VLPFC implementing action control.
Changes in conscious level have been associated with changes in dynamical integration and segregation among distributed brain regions. Recent theoretical developments emphasize changes in directed functional (i.e., causal) connectivity as reflected in quantities such as 'integrated information' and 'causal density'. Here we develop and illustrate a rigorous methodology for assessing causal connectivity from electroencephalographic (EEG) signals using Granger causality (GC). Our method addresses the challenges of non-stationarity and bias by dividing data into short segments and applying permutation analysis. We apply the method to EEG data obtained from subjects undergoing propofol-induced anaesthesia, with signals source-localized to the anterior and posterior cingulate cortices. We found significant increases in bidirectional GC in most subjects during loss-of-consciousness, especially in the beta and gamma frequency ranges. Corroborating a previous analysis we also found increases in synchrony in these ranges; importantly, the Granger causality analysis showed higher inter-subject consistency than the synchrony analysis. Finally, we validate our method using simulated data generated from a model for which GC values can be analytically derived. In summary, our findings advance the methodology of Granger causality analysis of EEG data and carry implications for integrated information and causal density theories of consciousness.
Cognition results from interactions among functionally specialized but widely distributed brain regions; however, neuroscience has so far largely focused on characterizing the function of individual brain regions and neurons therein. Here we discuss recent studies that have instead investigated the interactions between brain regions during cognitive processes by assessing correlations between neuronal oscillations in different regions of the primate cerebral cortex. These studies have opened a new window onto the large-scale circuit mechanisms underlying sensorimotor decision-making and top-down attention. We propose that frequency-specific neuronal correlations in large-scale cortical networks may be 'fingerprints' of canonical neuronal computations underlying cognitive processes.
Recent studies have established a relation between ongoing brain activity fluctuations and intertrial variability in evoked neural responses, perception, and motor performance. Here, we extended these investigations into the domain of cognitive control. Using functional neuroimaging and a sparse event-related design (with long and unpredictable intervals), we measured ongoing activity fluctuations and evoked responses in volunteers performing a Stroop task with color-word interference. Across trials, prestimulus activity of several regions predicted subsequent response speed and across subjects this effect scaled with the Stroop effect size, being significant only in subjects manifesting behavioral interference. These effects occurred only in task relevant as the dorsal anterior cingulate and dorsolateral prefrontal cortex as well as ventral visual areas sensitive to color and visual words. Crucially, in subjects showing a Stroop effect, reaction times were faster when prestimulus activity was higher in task-relevant (color) regions and slower when activity was higher in irrelevant (word form) regions. These findings suggest that intrinsic brain activity fluctuations modulate neural mechanisms underpinning selective voluntary attention and cognitive control. Rephrased in terms of predictive coding models, ongoing activity can hence be considered a proxy of the precision (gain) with which prediction error signals are transmitted upon sensory stimulation.
This paper describes FieldTrip, an open source software package that we developed for the analysis of MEG, EEG, and other electrophysiological data. The software is implemented as a MATLAB toolbox and includes a complete set of consistent and user-friendly high-level functions that allow experimental neuroscientists to analyze experimental data. It includes algorithms for simple and advanced analysis, such as time-frequency analysis using multitapers, source reconstruction using dipoles, distributed sources and beamformers, connectivity analysis, and nonparametric statistical permutation tests at the channel and source level. The implementation as toolbox allows the user to perform elaborate and structured analyses of large data sets using the MATLAB command line and batch scripting. Furthermore, users and developers can easily extend the functionality and implement new algorithms. The modular design facilitates the reuse in other software packages.
In recent years, studies ranging from single-unit recordings in animals to electroencephalography and magnetoencephalography studies in humans have demonstrated the pivotal role of phase synchronization in memory processes. Phase synchronization - here referring to the synchronization of oscillatory phases between different brain regions - supports both working memory and long-term memory and acts by facilitating neural communication and by promoting neural plasticity. There is evidence that processes underlying working and long-term memory might interact in the medial temporal lobe. We propose that this is accomplished by neural operations involving phase-phase and phase-amplitude synchronization. A deeper understanding of how phase synchronization supports the flexibility of and interaction between memory systems may yield new insights into the functions of phase synchronization in general.
Selectively retrieving episodic information from a cue often induces interference from related episodes. To promote successful retrieval of the target episode, such interference is resolved by inhibition, causing retrieval-induced forgetting of the related but irrelevant information. Passively studying the episodic information again (reexposure) does not show this effect. This study examined the hypothesis that brain oscillations in the theta band (5-9 Hz) reflect the dynamics of interference in selective memory retrieval, analyzing EEG data from 24 healthy human subjects (21 women, 3 men). High versus low levels of interference were investigated by comparing the effects of selective retrieval with the effects of reexposure of material, with the former, but not the latter, inducing interference. Moreover, we analyzed repeated cycles of selective retrieval and reexposure, assuming that interference is reduced by inhibition across retrieval cycles, but not across reexposure cycles. We found greater theta band activity in selective retrieval than in reexposure, and a reduction in theta amplitude from the first to the second cycle of retrieval predicting the amount of retrieval-induced forgetting; the sources of theta amplitude reduction across retrieval cycles were located in the anterior cingulate cortex. No difference in theta activity was found across repeated cycles of reexposure. The results suggest that higher levels of interference in episodic memory are indexed by more theta band activity, and that successful interference resolution via inhibition causes a reduction in theta amplitude. Thus, theta band activity can serve as a neural marker of the dynamics of interference in selective episodic retrieval.
Background:
EEG studies of working memory (WM) have demonstrated load dependent frequency band modulations. FMRI studies have localized load modulated activity to the dorsolateral prefrontal cortex (DLPFC), medial prefrontal cortex (MPFC), and posterior parietal cortex (PPC). Recently, an EEG-fMRI study found that low frequency band (theta and alpha) activity negatively correlated with the BOLD signal during the retention phase of a WM task. However, the coupling of higher (beta and gamma) frequencies with the BOLD signal during WM is unknown.
Methodology:
In 16 healthy adult subjects, we first investigated EEG-BOLD signal correlations for theta (5-7 Hz), alpha1 (8-10), alpha2 (10-12 Hz), beta1 (13-20), beta2 (20-30 Hz), and gamma (30-40 Hz) during the retention period of a WM task with set size 2 and 5. Secondly, we investigated whether load sensitive brain regions are characterised by effects that relate frequency bands to BOLD signals effects.
Principal findings:
We found negative theta-BOLD signal correlations in the MPFC, PPC, and cingulate cortex (ACC and PCC). For alpha1 positive correlations with the BOLD signal were found in ACC, MPFC, and PCC; negative correlations were observed in DLPFC, PPC, and inferior frontal gyrus (IFG). Negative alpha2-BOLD signal correlations were observed in parieto-occipital regions. Beta1-BOLD signal correlations were positive in ACC and negative in precentral and superior temporal gyrus. Beta2 and gamma showed only positive correlations with BOLD, e.g., in DLPFC, MPFC (gamma) and IFG (beta2/gamma). The load analysis revealed that theta and--with one exception--beta and gamma demonstrated exclusively positive load effects, while alpha1 showed only negative effects.
Conclusions:
We conclude that the directions of EEG-BOLD signal correlations vary across brain regions and EEG frequency bands. In addition, some brain regions show both load sensitive BOLD and frequency band effects. Our data indicate that lower as well as higher frequency brain oscillations are linked to neurovascular processes during WM.
Accomplishing even simple tasks depend on neuronal circuits to configure how incoming sensory stimuli map onto responses. Controlling these stimulus-response (SR) mapping rules relies on a cognitive control network comprising the anterior cingulate cortex (ACC). Single neurons within the ACC convey information about currently relevant SR mapping rules and signal unexpected action outcomes, which can be used to optimize behavioral choices. However, its functional significance and the mechanistic means of interaction with other nodes of the cognitive control network remain elusive and poorly understood. Here, we report that core aspects of cognitive control are encoded by rhythmic theta-band activity within neuronal circuits in the ACC. Throughout task performance, theta-activity predicted which of two SR mapping rules will be established before processing visual target information. Task-selective theta-activity emerged particularly early during those trials, which required the adjustment of SR rules following an erroneous rule representation in the preceding trial. These findings demonstrate a functional correlation of cognitive control processes and oscillatory theta-band activity in macaque ACC. Moreover, we report that spike output of a subset of cells in ACC is synchronized to predictive theta-activity, suggesting that the theta-cycle could serve as a temporal reference for coordinating local task selective computations across a larger network of frontal areas and the hippocampus to optimize and adjust the processing routes of sensory and motor circuits to achieve efficient sensory-motor control.
Recent findings indicate that the hippocampus supports not only long-term memory encoding but also plays a role in working memory (WM) maintenance of multiple items; however, the neural mechanism underlying multi-item maintenance is still unclear. Theoretical work suggests that multiple items are being maintained by neural assemblies synchronized in the gamma frequency range (25-100 Hz) that are locked to consecutive phase ranges of oscillatory activity in the theta frequency range (4-8 Hz). Indeed, cross-frequency coupling of the amplitude of high-frequency activity to the phase of slower oscillations has been described both in animals and in humans, but has never been linked to a theoretical model of a cognitive process. Here we used intracranial EEG recordings in human epilepsy patients to test pivotal predictions from theoretical work. First, we show that simultaneous maintenance of multiple items in WM is accompanied by cross-frequency coupling of oscillatory activity in the hippocampus, which is recruited during multi-item WM. Second, maintenance of an increasing number of items is associated with modulation of beta/gamma amplitude with theta band activity of lower frequency, consistent with the idea that longer cycles are required for an increased number of representations by gamma cycles. This effect cannot be explained by a difference in theta or beta/gamma power. Third, we describe how the precision of cross-frequency coupling predicts individual WM performance. These data support the idea that working memory in humans depends on a neural code using phase information.
The behavioural adjustment that follows the experience of conflict has been extensively studied in humans, leading to influential models of executive-control adjustment. Recent studies have revealed striking similarities in conflict-induced behavioural adjustment between humans and monkeys, indicating that monkeys can provide a model to study the underlying neural substrates and mechanisms of such behaviour. These studies have advanced our knowledge about the role of different prefrontal brain regions, including the anterior cingulate cortex (ACC) and the dorsolateral prefrontal cortex (DLPFC), in executive-control adjustment and suggest a pivotal role for the DLPFC in the dynamic tuning of executive control and, consequently, in behavioural adaptation to changing environments.
Error-related activity in the medial prefrontal cortex (mPFC) is thought to work in conjunction with lateral prefrontal cortex (lPFC) as a part of an action-monitoring network, where errors signal the need for increased cognitive control. The neural mechanism by which this mPFC-lPFC interaction occurs remains unknown. We hypothesized that transient synchronous oscillations in the theta range reflect a mechanism by which these structures interact. To test this hypothesis, we extracted oscillatory phase and power from current-source-density-transformed electroencephalographic data recorded during a Flanker task. Theta power in the mPFC was diminished on the trial preceding an error and increased immediately after an error, consistent with predictions of an action-monitoring system. These power dynamics appeared to take place over a response-related background of oscillatory theta phase coherence. Theta phase synchronization between FCz (mPFC) and F5/6 (lPFC) sites was robustly increased during error trials. The degree of mPFC-lPFC oscillatory synchronization predicted the degree of mPFC power on error trials, and both of these dynamics predicted the degree of posterror reaction time slowing. Oscillatory dynamics in the theta band may in part underlie a mechanism of communication between networks involved in action monitoring and cognitive control.
Field potential oscillations at approximately 10 Hz (alpha rhythm) are widely noted in the visual cortices, but their physiological mechanisms and significance are poorly understood. In vitro studies have implicated pyramidal neurons in both infragranular and supragranular layers as pacemakers. The generality of these observations for the intact brain in the behaving subject is unknown. We analyzed laminar profiles of spontaneous local field potentials and multiunit activity (MUA) recorded with linear array multielectrodes from visual areas V2, V4, and inferotemporal (IT) cortex of two macaque monkeys during performance of a sensory discrimination task. Current source density (CSD) analysis was combined with CSD-MUA coherence to identify intracortical alpha current generators and their potential for alpha pacemaking. The role of each alpha current generator was further delineated by Granger causality analyses. In V2 and V4, alpha current generators were found in all layers, with the infragranular generator acting as primary local pacemaking generator. In contrast, in IT, alpha current generators were found only in supragranular and infragranular layers, with the supragranular generator acting as primary local pacemaking generator. The amplitude of alpha activity in V2 and V4 was negatively correlated with behavioral performance, whereas the opposite was true in IT. The alpha rhythm in IT thus appears to differ from that in the lower-order cortices, both in terms of its underlying physiological mechanism and its behavioral correlates. This work may help to reconcile some of the diverse findings and conclusions on the functional significance of alpha band oscillations in the visual system.
The literature on interference in the Stroop Color–Word Task, covering over 50 years and some 400 studies, is organized and reviewed. In so doing, a set of 18 reliable empirical findings is isolated that must be captured by any successful theory of the Stroop effect. Existing theoretical positions are summarized and evaluated in view of this critical evidence and the 2 major candidate theories—relative speed of processing and automaticity of reading—are found to be wanting. It is concluded that recent theories placing the explanatory weight on parallel processing of the irrelevant and the relevant dimensions are likely to be more successful than are earlier theories attempting to locate a single bottleneck in attention.
It has been shown in animals that neuronal activity in the 'gamma band' (>30 Hz) is associated with cortical activation and may play a role in multi-regional and multi-modal integration of cortical processing. Studies of gamma activity in human scalp EEG have typically focused on event-related synchronization (ERS) in the 40 Hz band. To assess further the gamma band ERS further, as an index of cortical activation and as a tool for human functional brain mapping, we recorded subdural electrocorticographic (ECoG) signals in five clinical subjects while they performed visual-motor decision tasks designed to activate the representations of different body parts in sensorimotor cortex. ECoG spectral analysis utilized a mixed-effects analysis of variance model in which within-trial temporal dependencies were accounted for. Taking an exploratory approach, we studied gamma ERS in 10-Hz-wide bands (overlapping by 5 Hz) ranging from 30 to 100 Hz, and compared these findings with changes in the alpha (8-13 Hz) and beta (15-25 Hz) bands. Gamma ERS (observed in three out of subjects) occurred in two broad bands-'low gamma' included the 35-45 and 40-50 Hz bands, and 'high gamma' the 75-85, 80-90, 85-95 and 90-100 Hz bands. The temporal and spatial characteristics of low and high gamma ERS were distinct, suggesting relatively independent neurophysiological mechanisms. Low gamma ERS often began after onset of the motor response and was sustained through much of it, in parallel with event-related desynchronization (ERD) in the alpha band. High gamma ERS often began during, or slightly before, the motor response and was transient, ending well before completion of the motor response. These temporal differences in low and high gamma suggest different functional associations with motor performance. Compared with alpha and beta ERD, the topographical patterns of low and high gamma ERS were more discrete and somatotopically specific and only occurred over contralateral sensorimotor cortex during unilateral limb movements (alpha and beta ERD were also observed ipsilaterally). Maps of sensorimotor function inferred from gamma ERS were consistent with maps generated by cortical electrical stimulation for clinical purposes. In addition, different task conditions in one subject produced consistent differences in both motor response latencies and onset latency of gamma ERS, particularly high gamma ERS. Compared with alpha and beta ERD, the topography of gamma ERS is more consistent with traditional maps of sensorimotor functional anatomy. In addition, gamma ERS may provide complementary information about cortical neurophysiology that is useful for mapping brain function in humans.
Human scalp EEG studies have shown that event-related desynchronization (ERD) in the alpha (8-13 Hz) and beta (15-25 Hz) bands may be used to detect functional activation of sensorimotor cortex. However, in most previous studies somatotopy has not been examined in detail and brief, self-paced movements, focusing on the planning of motor output, have been used. We recorded electrocorticographic (ECoG) signals in five clinical subjects during a visual-motor decision task that was designed to activate the representations of different body parts in sensorimotor cortex. To focus more on execution of motor output than on its planning, subjects were instructed to make sustained isometric muscle contractions in different body parts (tongue protrusion, fist-clenching or foot dorsiflexion) in response to randomized visual stimuli depicting each action. ECoG spectral analysis utilized a mixed-effects analysis of variance model in which within-trial temporal dependencies were taken into account, and the magnitude and statistical significance of alpha and beta ERDs were mapped onto a surface rendering of each subject's brain MRI. Cortical electrical stimulation was performed in all subjects for clinical purposes, and the resulting maps of sensorimotor function were compared with those generated by ECoG spectral analysis. During the early phases of the motor responses, alpha ERD commonly occurred in a diffuse spatial pattern that was not somatotopically specific. During the late phases, the spatial pattern of alpha ERD usually became more focused and somatotopically specific. Maps of alpha ERD were closer to cortical stimulation maps when alpha ERD was sustained throughout the late phases of the motor responses. Thus, the topography of alpha ERD more resembled traditional somatotopy when its temporal profile approximated that of the motor response. The topography of beta ERD was often more discrete and somatotopically specific than that of alpha ERD, but beta ERD was often transient and sometimes absent. Sometimes, unilateral limb movement produced sustained alpha and beta ERD over bilateral sensorimotor cortices, with overlapping patterns for different body parts. The topographical spread of alpha ERD beyond expected functional-anatomical boundaries during early (and sometimes late) phases of motor responses invites a re-examination of traditional assumptions about sensorimotor functional neuroanatomy, as well as the role of alpha ERD as an index of cortical activation. We agree with others that the somatotopic representations of different body parts overlap more than previously thought. Also, unilateral limb movements may be associated with both contralateral and ipsilateral activation of sensorimotor cortex. We conjecture that alpha ERD may reflect activity within a broad synaptic network with distributed cortical representations.
In this article we consider the application of parametric spectral analysis to multichannel event-related potentials (ERPs) during cognitive experiments. We show that with proper data preprocessing, Adaptive MultiVariate AutoRegressive (AMVAR) modeling is an effective technique for dealing with nonstationary ERP time series. We propose a bootstrap procedure to assess the variability in the estimated spectral quantities. Finally, we apply AMVAR spectral analysis to a visuomotor integration task, revealing rapidly changing cortical dynamics during different stages of task processing.
The emergence of a unified cognitive moment relies on the coordination
of scattered mosaics of functionally specialized brain regions. Here we review
the mechanisms of large-scale integration that counterbalance the distributed
anatomical and functional organization of brain activity to enable the emergence
of coherent behaviour and cognition. Although the mechanisms involved in large-scale
integration are still largely unknown, we argue that the most plausible candidate
is the formation of dynamic links mediated by synchrony over multiple frequency
bands.
In humans, distinct processes within the hippocampus and rhinal cortex support declarative memory formation. But do these medial temporal lobe (MTL) substructures directly cooperate in encoding new memories? Phase synchronization of gamma-band electroencephalogram (EEG) oscillations (around 40 Hz) is a general mechanism of transiently connecting neural assemblies. We recorded depth-EEG from within the MTL of epilepsy patients performing a memorization task. Successful as opposed to unsuccessful memory formation was accompanied by an initial elevation of rhinal-hippocampal gamma synchronization followed by a later desynchronization, suggesting that effective declarative memory formation is accompanied by a direct and temporarily limited cooperation between both MTL substructures.
According to the 'conflict-monitoring' model, a leading theory of cognitive control1, 2, 3, ⁴, information-processing conflict registered in the anterior cingulate cortex (ACC) triggers the prefrontal cortex to reduce conflict susceptibility. Here we show that the existing empirical support for an online modulation of susceptibility to conflict through immediately preceding conflict, the 'conflict-adaptation effect'1, ⁵, needs to be reevaluated. In a human cognitive control task, we found that it was not the stimulus-independent level of conflict that was responsible for the conflict-adaptation effect but rather an episodic memory phenomenon: stimulus-specific priming⁶.
Conflict monitoring by the anterior cingulate cortex (ACC) has been posited to signal a need for greater cognitive control,
producing neural and behavioral adjustments. However, the very occurrence of behavioral adjustments after conflict has been
questioned, along with suggestions that there is no direct evidence of ACC conflict-related activity predicting subsequent
neural or behavioral adjustments in control. Using the Stroop color-naming task and controlling for repetition effects, we
demonstrate that ACC conflict-related activity predicts both greater prefrontal cortex activity and adjustments in behavior,
supporting a role of ACC conflict monitoring in the engagement of cognitive control.
Previous studies have shown that synchronized beta frequency (14-30 Hz) oscillations in the primary motor cortex are involved in maintaining steady contractions of contralateral arm and hand muscles. However, little is known about the role of postcentral cortical areas in motor maintenance and their patterns of interaction with motor cortex. We investigated the functional relations of beta-synchronized neuronal assemblies in pre- and postcentral areas of two monkeys as they pressed a hand lever during the wait period of a visual discrimination task. By using power and coherence spectral analysis, we identified a beta-synchronized large-scale network linking pre- and postcentral areas. We then used Granger causality spectra to measure directional influences among recording sites. In both monkeys, strong Granger causal influences were observed from primary somatosensory cortex to both motor cortex and inferior posterior parietal cortex, with the latter area also exerting Granger causal influences on motor cortex. Granger causal influences from motor cortex to postcentral sites, however, were weak in one monkey and not observed in the other. These results are the first, to our knowledge, to demonstrate in awake monkeys that synchronized beta oscillations bind multiple sensorimotor areas into a large-scale network during motor maintenance behavior and carry Granger causal influences from primary somatosensory and inferior posterior parietal cortices to motor cortex.
Clocks tick, bridges and skyscrapers vibrate, neuronal networks oscillate. Are neuronal oscillations an inevitable by-product,
similar to bridge vibrations, or an essential part of the brain's design? Mammalian cortical neurons form behavior-dependent
oscillating networks of various sizes, which span five orders of magnitude in frequency. These oscillations are phylogenetically
preserved, suggesting that they are functionally relevant. Recent findings indicate that network oscillations bias input selection,
temporally link neurons into assemblies, and facilitate synaptic plasticity, mechanisms that cooperatively support temporal
representation and long-term consolidation of information.
Human anterior cingulate cortex (ACC) activity modulation has been observed in numerous tasks, consistent with a wide variety of functions. However, previous recordings have not had sufficient spatial resolution to determine whether microdomains (approximately one to two columns) are involved in multiple tasks, how activity is distributed across cortical layers, or indeed whether modulation reflected neuronal excitation, inhibition, or both. In this study, linear arrays of 24 microelectrodes were used to estimate population synaptic currents and neuronal firing in different layers of ACC during simple/choice reaction time, delayed word recognition, rhyming, auditory oddball, and cued conditional letter-discrimination tasks. Responses to all tasks, with differential responses to errors, familiarity, difficulty, and orienting, were recorded in single microdomains. The strongest responses occurred approximately 300-800 ms after stimulus onset and were usually a current source with inhibited firing, strongly suggesting active inhibition in superficial layers during the behavioral response period. This was usually followed by a sink from approximately 800 to 1400 ms, consistent with postresponse rebound activation. Transient phase locking of task-related theta activity in superficial cingulate layers suggested extended interactions with medial and lateral frontal and temporal sites. These data suggest that each anterior cingulate microdomain participates in a multilobar cortical network after behavioral responses in a variety of tasks.
Top-down attentional control is required when subjects must attend to one of multiple conflicting stimulus features, such as in the Stroop task. Performance may be improved when such control is implemented in advance of stimulus presentation, yet few studies have examined this issue. Our investigation employed a spatial Stroop task with a manual response, allowing us to focus on the effects of preparatory attention on verbal processing when it is the less automatic attribute. A letter cue (P or W) presented for 2200 msec instructed subjects to respond on the basis of the position or meaning of a word (up, down, left, right) placed in an incongruent position relative to center. Event-related potentials recorded during pre- and poststimulus periods were analyzed as a function of reaction time to the target stimulus (fast vs. slow) in order to differentiate neural activity associated with more or less successful implementation of control. During the prestimulus period, fast responses to subsequent targets were associated with enhanced slow-wave activity over right frontal and bilateral central-parietal regions. During the poststimulus period, fast word trials were uniquely associated with an enhanced inferior temporal negativity (ITN) from 200 to 600 msec. More importantly, a correlation between frontal prestimulus activity and the poststimulus ITN suggested that frontal preparatory activity played a role in facilitating conceptual processing of the verbal stimulus when it arrived, providing an important link between preparatory attention and mechanisms that improve performance in the face of conflict.
Voluntary movements are accompanied by amplitude changes in cortical rhythms presumably as a result of functional activation of sensorimotor areas. Recently, the location of the neural generators involved in increasing power within the beta (15-30 Hz) frequency band following movement (post-movement beta rebound, PMBR) has come into question [Parkes, L.M, Bastiaansen, M.C.M, Norris, D.G., 2006. Combining EEG and fMRI to investigate the post-movement beta rebound. NeuroImage 29, 685-696.]. We used the synthetic aperture magnetometry (SAM) spatial filtering method to identify the time course and location of oscillatory changes within the beta and mu (8-14 Hz) frequency bands during the performance of voluntary movements. Neuromagnetic activity was recorded from 10 adult subjects during abduction of the right index finger. Changes in beta and mu source power were calculated for periods during and following movement, relative to pre-movement baseline activity. Decreases in beta band activity (event-related desynchronization, ERD) were observed during movement, with a strong increase (PMBR) beginning 230+/-170 ms following movement, lasting for 680+/-170 ms. Mu band ERD was observed both during and following movement, with little to no post-movement rebound. Beta and mu ERD were localized bilaterally to the hand region of postcentral gyrus whereas PMBR was localized bilaterally to the hand region of precentral gyrus (motor cortex). Both PMBR and beta ERD were strongest contralateral to the side of movement. These results provide further evidence that movement influences independent cortical rhythms in sensorimotor areas, and confirm previous reports of precentral generators of PMBR in the region of motor cortex, with postcentral generators of beta and mu ERD during movement.
Theories of the regulation of cognition suggest a system with two necessary components: one to implement control and another to monitor performance and signal when adjustments in control are needed. Event-related functional magnetic resonance imaging and a task-switching version of the Stroop task were used to examine whether these components of cognitive control have distinct neural bases in the human brain. A double dissociation was found. During task preparation, the left dorsolateral prefrontal cortex (Brodmann's area 9) was more active for color naming than for word reading, consistent with a role in the implementation of control. In contrast, the anterior cingulate cortex (Brodmann's areas 24 and 32) was more active when responding to incongruent stimuli, consistent with a role in performance monitoring.
This article presents, for the first time, a practical method for the direct quantification of frequency-specific synchronization (i.e., transient phase-locking) between two neuroelectric signals. The motivation for its development is to be able to examine the role of neural synchronies as a putative mechanism for long-range neural integration during cognitive tasks. The method, called phase-locking statistics (PLS), measures the significance of the phase covariance between two signals with a reasonable time-resolution (<100 ms). Unlike the more traditional method of spectral coherence, PLS separates the phase and amplitude components and can be directly interpreted in the framework of neural integration. To validate synchrony values against background fluctuations, PLS uses surrogate data and thus makes no a priori assumptions on the nature of the experimental data. We also apply PLS to investigate intracortical recordings from an epileptic patient performing a visual discrimination task. We find large-scale synchronies in the gamma band (45 Hz), e.g., between hippocampus and frontal gyrus, and local synchronies, within a limbic region, a few cm apart. We argue that whereas long-scale effects do reflect cognitive processing, short-scale synchronies are likely to be due to volume conduction. We discuss ways to separate such conduction effects from true signal synchrony.
Assessing directed functional connectivity from time series data is a key challenge in neuroscience. One approach to this problem leverages a combination of Granger causality analysis and network theory. This article describes a freely available MATLAB toolbox – ‘Granger causal connectivity analysis’ (GCCA) – which provides a core set of methods for performing this analysis on a variety of neuroscience data types including neuroelectric, neuromagnetic, functional MRI, and other neural signals. The toolbox includes core functions for Granger causality analysis of multivariate steady-state and event-related data, functions to preprocess data, assess statistical significance and validate results, and to compute and display network-level indices of causal connectivity including ‘causal density’ and ‘causal flow’. The toolbox is deliberately small, enabling its easy assimilation into the repertoire of researchers. It is however readily extensible given proficiency with the MATLAB language.
We present evidence that a multitude of mid-frontal event-related potential (ERP) components partially reflect a common theta band oscillatory process. Specifically, mid-frontal ERP components in the N2 time range and error-related negativity time range are parsimoniously characterized as reflections of theta band activities. Forty participants completed three different tasks with varying stimulus-response demands. Permutation tests were used to identify the dominant time-frequency responses of stimulus- and response-locked conditions as well as the enhanced responses to novelty, conflict, punishment, and error. A dominant theta band feature was found in all conditions, and both ERP component amplitudes and theta power measures were similarly modulated by novelty, conflict, punishment, and error. The findings support the hypothesis that generic and reactive medial prefrontal cortex processes are parsimoniously reflected by theta band activities.
In making decisions, people have to balance between the competing demands of speed and accuracy, a balance generally referred to as the speed-accuracy tradeoff (SAT). In this study, we investigated the role of controlled SAT in a two-choice task in which manual responses were either validly or invalidly cued. Examining electrophysiological measurements of oscillatory brain activity, theta power in the anterior cingulate cortex (ACC), alpha power in the occipital cortex, and beta power in the motor cortex were found to be related to SAT. Because oscillatory effects of SAT were found to emanate from the SAT baseline interval preceding the two-choice task, the results indicate that SAT is modulated by a change of visuo-motor baseline activities rather than a change of response threshold. Moreover, in the two-choice task, conflict-induced theta power in the ACC was found to be more pronounced in speed than in accuracy trials, whereas priming-related beta power dynamics in the motor cortex were unaffected by SAT. These results indicate that conflict processing, but not response priming, depends on SAT.
Recent studies suggest that cross-frequency coupling (CFC) might play a functional role in neuronal computation, communication and learning. In particular, the strength of phase-amplitude CFC differs across brain areas in a task-relevant manner, changes quickly in response to sensory, motor and cognitive events, and correlates with performance in learning tasks. Importantly, whereas high-frequency brain activity reflects local domains of cortical processing, low-frequency brain rhythms are dynamically entrained across distributed brain regions by both external sensory input and internal cognitive events. CFC might thus serve as a mechanism to transfer information from large-scale brain networks operating at behavioral timescales to the fast, local cortical processing required for effective computation and synaptic modification, thus integrating functional systems across multiple spatiotemporal scales.
The human brain executes cognitive control, such as selection of relevant information in the presence of competing irrelevant information, and cognitive control is essential for us to yield a series of optimal behaviors in our daily life. This study assessed electrocorticographic γ-oscillations elicited by cognitive control in the context of the Stroop color-naming paradigm, with a temporal resolution of 10 msec and spatial resolution of 1 cm. Subjects were instructed to overtly read a color word printed in an incongruent color in the reading task, and to overtly name the ink color of a color word printed in an incongruent color in the Stroop color-naming task. The latter task specifically elicited larger γ-augmentations in the dorsolateral-premotor, dorsolateral-prefrontal and supplementary motor areas with considerable inter-subject spatial variability. Such Stroop color-naming-specific γ-augmentations occurred 500 to 200 msec prior to overt responses. Electrical stimulation of the sites showing Stroop color-naming-specific γ-augmentations resulted in temporary naming impairment more frequently than that of the remaining sites. This study has provided direct evidence that a critical process of cognitive control in the context of Stroop color-naming paradigm consists of recruitment of neurons essential for naming located in variable portions of the dorsolateral premotor and prefrontal areas.
The prefrontal cortex (PFC) is thought to modulate the neural network state in favor of the processing of task-relevant sensory information prior to the presentation of sensory stimuli. However, this proactive control mechanism cannot always optimize the network state because of intrinsic fluctuation of neural activity upon arrival of sensory information. In the present study, we have investigated an additional control mechanism, in which the control process to regulate the behavior is adjusted to the trial-by-trial fluctuation in neural representations of sensory information. We asked normal human subjects to perform a variant of the Stroop task. Using functional magnetic resonance imaging, we isolated cognitive conflict at a sensory processing stage on a single-trial basis by calculating the difference in activation between task-relevant and task-irrelevant sensory areas. Activation in the dorsolateral PFC (DLPFC) covaried with the neural estimate of sensory conflict only on incongruent trials. Also, the coupling between the DLPFC and anterior cingulate cortex (ACC) was tighter on high-sensory conflict trials with fast response. The results suggest that although detection of sensory conflict is achieved by the DLPFC, online behavioral adjustment is achieved by interactive mechanisms between the DLPFC and ACC.
Successful information processing requires the focusing of attention on a certain stimulus property and the simultaneous suppression of irrelevant information. The Stroop task is a useful paradigm to study such attentional top-down control in the presence of interference. Here, we investigated the neural correlates of an auditory Stroop task using fMRI. Subjects focused either on tone pitch (relatively high or low; phonetic task) or on the meaning of a spoken word (high/low/good; semantic task), while ignoring the other stimulus feature. We differentiated between task-related (phonetic incongruent vs. semantic incongruent) and sensory-level interference (phonetic incongruent vs. phonetic congruent). Task-related interference activated similar regions as in visual Stroop tasks, including the anterior cingulate cortex (ACC) and the presupplementary motor-area (pre-SMA). More specifically, we observed that the very caudal/posterior part of the ACC was activated and not the dorsal/anterior region. Because identical stimuli but different task demands are compared in this contrast, it reflects conflict at a relatively high processing level. A more conventional contrast between incongruent and congruent phonetic trials was associated with a different cluster in the pre-SMA/ACC which was observed in a large number of previous studies. Finally, functional connectivity analysis revealed that activity within the regions activated in the phonetic incongruent vs. semantic incongruent contrast was more strongly interrelated during semantically vs. phonetically incongruent trials. Taken together, we found (besides activation of regions well-known from visual Stroop tasks) activation of the very caudal and posterior part of the ACC due to task-related interference in an auditory Stroop task.
The medial frontal cortex (MFC) has been implicated in the monitoring and selection of actions in the face of competing alternatives, but much remains unknown about its functional properties, including electrophysiological oscillations, during response conflict tasks. Here, we recorded intracranial EEG during a modified Flanker task from the MFC of two patients undergoing pre-surgical evaluation for the treatment of epilepsy. Performance on the task was associated with a suppression of beta (15-30 Hz) frequency oscillation power prior to and just following the response and an enhancement of theta (4-8 Hz) frequency power following the response. Beta (theta) power was anatomically distributed towards more dorsal/caudal (rostral/ventral) electrode sites along the cortex, suggesting an anatomical/functional specialization along the medial frontal wall for pre-response versus post-response action monitoring. Inter-site phase coherence analyses demonstrated that the ventral/rostral MFC theta oscillations were coupled with theta oscillations observed at scalp electrodes Fz and Cz. One patient was tested before and after having epileptogenic tissue in the MFC surgically removed; task performance increased from chance levels to near-perfect, and an ERP conflict effect was observed only following surgery. These findings provide novel evidence for the role of MFC oscillations and their relation to surface EEG-recorded potentials during action monitoring.
Median reaction times and intra-individual variability were studied in epileptic (N = 63), brain-damaged (non-epileptic) (N = 25) and control patients (N = 25) using a six and one half minute visual, continuous reaction time task. Epileptic and brain-damaged groups were significantly slower than control patients on median reaction times at the 10th, 50th, and 90th percentiles and on the differences between the 10th and 90th percentiles. Thus both general slowing and greater intra-individual variability were found in the epileptic and brain-damaged patients. Reaction times were not related to presence, type and severity of EEG abnormality or to age of onset of epilepsy. Grand mal patients did have significantly greater variability than other types of seizure patients. Epileptic and brain-damaged patients did not differ significantly on any reaction time variables. Both groups were discriminated significantly from the controls on all reaction time measures, especially on the intra-individual variability measure.
Recent studies indicate that subjects may respond to visual information during either an early parallel phase or a later focused phase and that the selection of the relevant phase is data driven. Using the noise-compatibility paradigm, we tested the hypothesis that this selection may also be strategic and context driven. At least part of the interference effect observed in this paradigm is due to response activation during the parallel-processing phase. We manipulated subjects' expectancies for compatible and incompatible noise in 4 experiments and effectively modulated the interference effect. The results suggest that expectancies about the relative utility of the information extracted during the parallel and focused phases determine which phase is used to activate responses.
Reaction time, attention, and impulsivity were studied in 112 children with epilepsy (4.5-13 years) using a computerized test. We measured simple reaction time (response with each hand separately to a single stimulus), forced choice reaction time (two stimuli presented in random order, one designated for each hand), and choice reaction time with distraction (two response stimuli, one for each hand, with two additional distracting stimuli randomly inserted). We also measured variability of speed of response and errors of omission and commission. Controls were unaffected children of similar age, ethnic, and socioeconomic backgrounds. Children with epilepsy were significantly slower, more variable, and made more omission errors than control children, even when analysis was limited to epileptic patients with IQ greater than 90, but they did not make more commission (i.e., impulsive) errors. Reaction times were related to IQ, but in general were not related to seizure severity, duration of seizure disorder, or duration of medication use. Untreated patients (N = 13) did not differ from those with antiepileptic drug levels in the therapeutic range on the day of testing (N = 52), but differed significantly from normal patients. Epileptic patients demonstrated significant slowing of reaction time and inattention, but not significant impulsivity, compared to normal children; however, these deficits do not appear to be related specifically to seizure history or treatment.
An internally or externally paced event results not only in the generation of an event-related potential (ERP) but also in a change in the ongoing EEG/MEG in form of an event-related desynchronization (ERD) or event-related synchronization (ERS). The ERP on the one side and the ERD/ERS on the other side are different responses of neuronal structures in the brain. While the former is phase-locked, the latter is not phase-locked to the event. The most important difference between both phenomena is that the ERD/ERS is highly frequency band-specific, whereby either the same or different locations on the scalp can display ERD and ERS simultaneously. Quantification of ERD/ERS in time and space is demonstrated on data from a number of movement experiments.
The anterior cingulate cortex (ACC), on the medial surface of the frontal lobes of the brain, is widely believed to be involved in the regulation of attention. Beyond this, however, its specific contribution to cognition remains uncertain. One influential theory has interpreted activation within the ACC as reflecting 'selection-for-action', a set of processes that guide the selection of environmental objects as triggers of or targets for action. We have proposed an alternative hypothesis, in which the ACC serves not to exert top-down attentional control but instead to detect and signal the occurrence of conflicts in information processing. Here, to test this theory against the selection-for-action theory, we used functional magnetic resonance imaging to measure brain activation during performance of a task where, for a particular subset of trials, the strength of selection-for-action is inversely related to the degree of response conflict. Activity within the ACC was greater during trials featuring high levels of conflict (and weak selection-for-action) than during trials with low levels of conflict (and strong selection-for-action), providing evidence in favour of the conflict-monitoring account of ACC function.
Cortical activity and perception are not driven by the external stimulus alone; rather sensory information has to be integrated with various other internal constraints such as expectations, recent memories, planned actions, etc. The question is how large scale integration over many remote and size-varying processes might be performed by the brain. We have conducted a series of EEG recordings during processes thought to involve neuronal assemblies of varying complexity. While local synchronization during visual processing evolved in the gamma frequency range, synchronization between neighboring temporal and parietal cortex during multimodal semantic processing evolved in a lower, the beta1 (12-18 Hz) frequency range, and long range fronto-parietal interactions during working memory retention and mental imagery evolved in the theta and alpha (4-8 Hz, 8-12 Hz) frequency range. Thus, a relationship seems to exist between the extent of functional integration and the synchronization-frequency. In particular, long-range interactions in the alpha and theta ranges seem specifically involved in processing of internal mental context, i.e. for top-down processing. We propose that large scale integration is performed by synchronization among neurons and neuronal assemblies evolving in different frequency ranges.
A neglected question regarding cognitive control is how control processes might detect situations calling for their involvement. The authors propose here that the demand for control may be evaluated in part by monitoring for conflicts in information processing. This hypothesis is supported by data concerning the anterior cingulate cortex, a brain area involved in cognitive control, which also appears to respond to the occurrence of conflict. The present article reports two computational modeling studies, serving to articulate the conflict monitoring hypothesis and examine its implications. The first study tests the sufficiency of the hypothesis to account for brain activation data, applying a measure of conflict to existing models of tasks shown to engage the anterior cingulate. The second study implements a feedback loop connecting conflict monitoring to cognitive control, using this to simulate a number of important behavioral phenomena.
The central problem for cognitive neuroscience is to describe how cognitive processes arise from brain processes. This review summarizes the recent evidence that synchronous neural oscillations reveal much about the origin and nature of cognitive processes such as memory, attention and consciousness. Memory processes are most closely related to theta and gamma rhythms, whereas attention seems closely associated with alpha and gamma rhythms. Conscious awareness may arise from synchronous neural oscillations occurring globally throughout the brain rather than from the locally synchronous oscillations that occur when a sensory area encodes a stimulus. These associations between the dynamics of the brain and cognitive processes indicate progress towards a unified theory of brain and cognition.
Adaptive goal-directed behavior involves monitoring of ongoing actions and performance outcomes, and subsequent adjustments
of behavior and learning. We evaluate new findings in cognitive neuroscience concerning cortical interactions that subserve
the recruitment and implementation of such cognitive control. A review of primate and human studies, along with a meta-analysis
of the human functional neuroimaging literature, suggest that the detection of unfavorable outcomes, response errors, response
conflict, and decision uncertainty elicits largely overlapping clusters of activation foci in an extensive part of the posterior
medial frontal cortex (pMFC). A direct link is delineated between activity in this area and subsequent adjustments in performance.
Emerging evidence points to functional interactions between the pMFC and the lateral prefrontal cortex (LPFC), so that monitoring-related
pMFC activity serves as a signal that engages regulatory processes in the LPFC to implement performance adjustments.
One hypothesis concerning the human dorsal anterior cingulate cortex (ACC) is that it functions, in part, to signal the occurrence of conflicts in information processing, thereby triggering compensatory adjustments in cognitive control. Since this idea was first proposed, a great deal of relevant empirical evidence has accrued. This evidence has largely corroborated the conflict-monitoring hypothesis, and some very recent work has provided striking new support for the theory. At the same time, other findings have posed specific challenges, especially concerning the way the theory addresses the processing of errors. Recent research has also begun to shed light on the larger function of the ACC, suggesting some new possibilities concerning how conflict monitoring might fit into the cingulate's overall role in cognition and action.
Attentive behavior requires the ability to perform in the face of distraction. Distracting information can cause conflict at any level along the information processing stream. However, it is not yet known whether the brain has distinct subsystems dedicated to detecting and resolving these different forms of distraction. Although previous studies have localized brain activity during semantic and response conflict, no prior study has specifically determined whether these activations occur in distinct or overlapping regions. We used a modified version of the Stroop color-word task, by which we were able to separate semantic from response conflict. Behavioral data indicate that these two kinds of conflict both contribute to the overall Stroop interference effect, while fMRI data indicate that they elicit non-overlapping activation in anterior cingulate, prefrontal, and parietal brain regions. These results suggest that the brain has distinct but parallel attentional mechanisms for resolving these different forms of cognitive interference.
At any one moment, many neuronal groups in our brain are active. Microelectrode recordings have characterized the activation of single neurons and fMRI has unveiled brain-wide activation patterns. Now it is time to understand how the many active neuronal groups interact with each other and how their communication is flexibly modulated to bring about our cognitive dynamics. I hypothesize that neuronal communication is mechanistically subserved by neuronal coherence. Activated neuronal groups oscillate and thereby undergo rhythmic excitability fluctuations that produce temporal windows for communication. Only coherently oscillating neuronal groups can interact effectively, because their communication windows for input and for output are open at the same times. Thus, a flexible pattern of coherence defines a flexible communication structure, which subserves our cognitive flexibility.
In the hippocampus, oscillations in the theta and gamma frequency range occur together and interact in several ways, indicating that they are part of a common functional system. It is argued that these oscillations form a coding scheme that is used in the hippocampus to organize the readout from long-term memory of the discrete sequence of upcoming places, as cued by current position. This readout of place cells has been analyzed in several ways. First, plots of the theta phase of spikes vs. position on a track show a systematic progression of phase as rats run through a place field. This is termed the phase precession. Second, two cells with nearby place fields have a systematic difference in phase, as indicated by a cross-correlation having a peak with a temporal offset that is a significant fraction of a theta cycle. Third, several different decoding algorithms demonstrate the information content of theta phase in predicting the animal's position. It appears that small phase differences corresponding to jitter within a gamma cycle do not carry information. This evidence, together with the finding that principle cells fire preferentially at a given gamma phase, supports the concept of theta/gamma coding: a given place is encoded by the spatial pattern of neurons that fire in a given gamma cycle (the exact timing within a gamma cycle being unimportant); sequential places are encoded in sequential gamma subcycles of the theta cycle (i.e., with different discrete theta phase). It appears that this general form of coding is not restricted to readout of information from long-term memory in the hippocampus because similar patterns of theta/gamma oscillations have been observed in multiple brain regions, including regions involved in working memory and sensory integration. It is suggested that dual oscillations serve a general function: the encoding of multiple units of information (items) in a way that preserves their serial order. The relationship of such coding to that proposed by Singer and von der Malsburg is discussed; in their scheme, theta is not considered. It is argued that what theta provides is the absolute phase reference needed for encoding order. Theta/gamma coding therefore bears some relationship to the concept of "word" in digital computers, with word length corresponding to the number of gamma cycles within a theta cycle, and discrete phase corresponding to the ordered "place" within a word.