[Show abstract][Hide abstract] ABSTRACT: Transcranial current brain stimulation (tCS) is becoming increasingly popular as a non-pharmacological non-invasive neuromodulatory method that alters cortical excitability by applying weak electrical currents to the scalp via a pair of electrodes. Most applications of this technique have focused on enhancing motor and learning skills, as well as a therapeutic agent in neurological and psychiatric disorders. In these applications, similarly to lesion studies, tCS was used to provide a causal link between a function or behaviour and a specific brain region (e.g., primary motor cortex). Nonetheless, complex cognitive functions are known to rely on functionally connected multitude of brain regions with dynamically changing patterns of information flow rather than on isolated areas, which are most commonly targeted in typical tCS experiments. In this review article, we argue in favour of combining tCS method with other neuroimaging techniques (e.g. fMRI, EEG) and by employing state-of-the-art connectivity data analysis techniques (e.g. graph theory) to obtain a deeper understanding of the underlying spatiotemporal dynamics of functional connectivity patterns and cognitive performance. Finally, we discuss the possibilities of these combined techniques to investigate the neural correlates of human creativity and to enhance creativity.
[Show abstract][Hide abstract] ABSTRACT: Feedback processing is important for learning and therefore may affect the consolidation of skills. Considerable research demonstrates electrophysiological differences between correct and incorrect feedback, but how we learn from small versus large errors is usually overlooked. This study investigated electrophysiological differences when processing small or large error feedback during a time estimation task. Data from high-learners and low-learners were analyzed separately. In both high- and low-learners, large error feedback was associated with higher feedback-related negativity (FRN) and small error feedback was associated with a larger P300 and increased amplitude over the motor related areas of the left hemisphere. In addition, small error feedback induced larger desynchronization in the alpha and beta bands with distinctly different topographies between the two learning groups: The high-learners showed a more localized decrease in beta power over the left frontocentral areas, and the low-learners showed a widespread reduction in the alpha power following small error feedback. Furthermore, only the high-learners showed an increase in phase synchronization between the midfrontal and left central areas. Importantly, this synchronization was correlated to how well the participants consolidated the estimation of the time interval. Thus, although large errors were associated with higher FRN, small errors were associated with larger oscillatory responses, which was more evident in the high-learners. Altogether, our results suggest an important role of the motor areas in the processing of error feedback for skill consolidation.
Journal of Cognitive Neuroscience 05/2014; 26(5):1180-1193. · 4.49 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Creativity is the hallmark of human cognition and is behind every innovation, scientific discovery, piece of music, artwork, and idea that have shaped our lives, from ancient times till today. Yet scientific understanding of creative processes is quite limited, mostly due to the traditional belief that considers creativity as a mysterious puzzle, a paradox, defying empirical enquiry. Recently, there has been an increasing interest in revealing the neural correlates of human creativity. Though many of these studies, pioneering in nature, help demystification of creativity, but the field is still dominated by popular beliefs in associating creativity with "right brain thinking", "divergent thinking", "altered states" and so on (Dietrich and Kanso, 2010). In this article, we discuss a computational framework for creativity based on Baars' Global Workspace Theory (GWT; Baars, 1988) enhanced with mechanisms based on information theory. Next we propose a neurocognitive architecture of creativity with a strong focus on various facets (i.e., unconscious thought theory, mind wandering, spontaneous brain states) of un/pre-conscious brain responses. Our principal argument is that pre-conscious creativity happens prior to conscious creativity and the proposed computational model may provide a mechanism by which this transition is managed. This integrative approach, albeit unconventional, will hopefully stimulate future neuroscientific studies of the inscrutable phenomenon of creativity.
Frontiers in Human Neuroscience 01/2014; 8:540. · 2.91 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A crucial aspect of cognitive control and learning is the ability to integrate feedback, that is, to evaluate action outcomes and their deviations from the intended goals and to adjust behavior accordingly. However, how high-learners differ from low-learners in relation to feedback processing has not been characterized. Further, little is known about the underlying brain connectivity patterns during feedback processing. This study aimed to fill these gaps by analyzing electrical brain responses from healthy adult human participants while they performed a time estimation task with correct and incorrect feedback. As compared with low-learners, high-learners presented larger mid-frontal theta (4-8 Hz) oscillations and lower sensorimotor beta (17-24 Hz) oscillations in response to incorrect feedback. Further, high-learners showed larger theta connectivity from left central, associated with motor activity, to mid-frontal, associated with performance monitoring, immediately after feedback (0-0.3 s), followed by (from 0.3 to 0.6 s after feedback) a flux from mid-frontal to prefrontal, associated with executive functioning. We suggest that these results reflect two cognitive processes related to successful feedback processing: first, the obtained feedback is compared with the expected one, and second, the feedback history is updated based on this information. Our results also indicate that high- and low-learners differ not only on how they react to incorrect feedback, but also in relation to how their distant brain areas interact while processing both correct and incorrect feedback. This study demonstrates the neural underpinnings of individual differences in goal-directed adaptive behavior.
Journal of Neuroscience 01/2013; 33(5):2029-38. · 6.91 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Likelihood thought-action fusion (TAF-L) refers to a cognitive bias in which individuals believe that the mere thought of a negative event increases its likelihood of occurring in reality. TAF-L is most commonly associated with obsessive-compulsive disorder (OCD) but is also present in depression, generalized anxiety disorder and psychosis. We induced TAF-L in individuals with high (High-OC, N = 23) and low (Low-OC, N = 24) levels of OC traits, and used low resolution electromagnetic tomography (LORETA) to localise the accompanying electrical brain activity patterns. The results showed greater TAF-L in the High-OC than in the Low-OC group (p < .005), which was accompanied by significantly greater upper beta frequency (19-30 Hz) activity in the precuneus (p < .05). Further, the precuneus activity was positively correlated with self-reported magnitude of TAF-L (p < .01), suggesting a specific role of this region in this cognitive bias. Results are discussed with reference to self-referential processing and the default-mode network.
[Show abstract][Hide abstract] ABSTRACT: Current behavioural and electrophysiological evidence suggests that music and language syntactic processing depends on at least partly shared neural resources. Existing studies using a simultaneous presentation paradigm are limited to the effects of violations of harmonic structure in Western tonal music on processing of single syntactic or semantic violations. Because melody is a universal property of music as it is emphasized also by non-western musical traditions, it is fundamental to investigate interactions between melodic expectation and language processing. The present study investigates the effect of melodically unexpected notes on neural responses elicited by linguistic violations. Sentences with or without a violation in the last word were presented on screen simultaneously with melodies whose last note had a high- or low-probability, as estimated by a computational model of melodic expectation. Violations in language could be syntactic, semantic or combined. The electroencephalogram (EEG) was recorded while participants occasionally responded to language stimuli. Confirming previous studies, low-probability notes elicited an enhanced N1 compared to high-probability notes. Further, syntactic violations elicited a left anterior negativity (LAN) and P600 component, and semantic violations elicited an N400. Combined violations elicited components which resembled neural responses to both syntactic and semantic incongruities. The LAN amplitude was decreased when language syntactic violations were presented simultaneously with low-probability notes compared to when they were presented with high-probability notes. The N400 was not influenced by the note-probability. These findings show support for the neural interaction between language and music processing, including novel evidence for melodic processing which can be incorporated in a computational framework of melodic expectation.
[Show abstract][Hide abstract] ABSTRACT: Preference formation is a complex problem as it is subjective, involves emotion, is led by implicit processes, and changes depending on the context even within the same individual. Thus, scientific attempts to predict preference are challenging, yet quite important for basic understanding of human decision making mechanisms, but prediction in a group-average sense has only a limited significance. In this study, we predicted preferential decisions on a trial by trial basis based on brain responses occurring before the individuals made their decisions explicit. Participants made a binary preference decision of approachability based on faces while their electrophysiological responses were recorded. An artificial neural network based pattern-classifier was used with time-frequency resolved patterns of a functional connectivity measure as features for the classifier. We were able to predict preference decisions with a mean accuracy of 74.3 ± 2.79% at participant-independent level and of 91.4 ± 3.8% at participant-dependent level. Further, we revealed a causal role of the first impression on final decision and demonstrated the temporal trajectory of preference decision formation.
PLoS ONE 01/2012; 7(8):e43351. · 3.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Here we discuss the remarkable role of the statistical memory effects in the human brain functioning at photosensitive epilepsy (PSE). We have analyzed three independent statistical memory quantifiers for the magnetoencephalographic (MEG) signals. These quantifiers reflect the dynamical characteristics of neuromagnetic brain responses to a flickering stimulus of different color combinations. Results for a group of control subjects are contrasted with those from a patient with PSE. The emergence of the strong memory and the transition to a regular and robust regime of chaotic behavior of the signals in separate areas is characteristic for a patient with PSE versus a healthy brain.
International Journal of Bifurcation and Chaos 11/2011; 18(09). · 0.92 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Electrophysiological studies investigating similarities between music and language perception have relied exclusively on the signal averaging technique, which does not adequately represent oscillatory aspects of electrical brain activity that are relevant for higher cognition. The current study investigated the patterns of brain oscillations during simultaneous processing of music and language using visually presented sentences and auditorily presented chord sequences. Music-syntactically regular or irregular chord functions were presented in sync with syntactically or semantically correct or incorrect words. Irregular chord functions (presented simultaneously with a syntactically correct word) produced an early (150-250 ms) spectral power decrease over anterior frontal regions in the theta band (5-7 Hz) and a late (350-700 ms) power increase in both the delta and the theta band (2-7 Hz) over parietal regions. Syntactically incorrect words (presented simultaneously with a regular chord) elicited a similar late power increase in delta-theta band over parietal sites, but no early effect. Interestingly, the late effect was significantly diminished when the language-syntactic and music-syntactic irregularities occurred at the same time. Further, the presence of a semantic violation occurring simultaneously with regular chords produced a significant increase in later delta-theta power at posterior regions; this effect was marginally decreased when the identical semantic violation occurred simultaneously with a music syntactical violation. Altogether, these results show that low frequency oscillatory networks get activated during the syntactic processing of both music and language, and further, these networks may possibly be shared.
Brain and Language 06/2011; 119(1):50-7. · 3.39 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This study investigated the interaction between sampling behavior and preference formation underlying subjective decision making for like and dislike decisions. Two-alternative forced-choice tasks were used with closely-matched musical excerpts and the participants were free to listen and re-listen, i.e. to sample and resample each excerpt, until they reached a decision. We predicted that for decisions involving resampling, a sampling bias would be observed before the moment of conscious decision for the like decision only. The results indeed showed a gradually increasing sampling bias favouring the choice (73%) before the moment of overt response for like decisions. Such a bias was absent for dislike decisions. Furthermore, the participants reported stronger relative preferences for like decisions as compared to dislike decisions. This study demonstrated distinct differences in preference formation between like and dislike decisions, both in the implicit orienting/sampling processes prior to the conscious decision and in the subjective evaluation afterwards.
Consciousness and Cognition 02/2011; 20(4):1781-6. · 2.31 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We analyze the topography of nonlinear functional connectivity in the EEG of two groups of German-native speakers, divided according to their English proficiency level (high or low), when listening to one text in German and one in English. Global interdependence was assessed in full-band EEG by means of an index of multivariate correlation derived from the normalized cross-mutual information between every two electrodes within each region of interest (ROI): three interhemispheric (frontal, centro-temporal and parietooccipital) and two intrahemispheric ones (left and right hemisphere). The results show clear topographic differences between the interhemispheric ROIs, but no differences between the intrahemispheric ROIs. Furthermore, there are also differences in language processing that depend on the proficiency level. We discuss these results and their implication along with recent findings on phase synchronization in the gamma band during second language processing.
Advances in Artificial Intelligence - 14th Conference of the Spanish Association for Artificial Intelligence, CAEPIA 2011, La Laguna, Spain, November 7-11, 2011. Proceedings; 01/2011
[Show abstract][Hide abstract] ABSTRACT: Recent research has shown that extensive training in and exposure to a second language can modify the language organization in the brain by causing both structural and functional changes. However it is not yet known how these changes are manifested by the dynamic brain oscillations and synchronization patterns subserving the language networks. In search for synchronization correlates of proficiency and expertise in second language acquisition, multivariate EEG signals were recorded from 44 high and low proficiency bilinguals during processing of natural language in their first and second languages. Gamma band (30-45 Hz) phase synchronization (PS) was calculated mainly by two recently developed methods: coarse-graining of Markov chains (estimating global phase synchrony, measuring the degree of PS between one electrode and all other electrodes), and phase lag index (PLI; estimating bivariate phase synchrony, measuring the degree of PS between a pair of electrodes). On comparing second versus first language processing, global PS by coarse-graining Markov chains indicated that processing of the second language needs significantly higher synchronization strength than first language. On comparing the proficiency groups, bivariate PS measure (i.e., PLI) revealed that during second language processing the low proficiency group showed stronger and broader network patterns than the high proficiency group, with interconnectivities between a left fronto-parietal network. Mean phase coherence analysis also indicated that the network activity was globally stronger in the low proficiency group during second language processing.
Frontiers in Psychology 01/2011; 2:334. · 2.80 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The neuromagnetic activity (magnetoencephalogram, MEG) from healthy human brain and from an epileptic patient against chromatic flickering stimuli has been earlier analyzed on the basis of a memory functions formalism (MFF). Information measures of memory as well as relaxation parameters revealed high individuality and unique features in the neuromagnetic brain responses of each subject. The current paper demonstrates new capabilities of MFF by studying cross-correlations between MEG signals obtained from multiple and distant brain regions. It is shown that the MEG signals of healthy subjects are characterized by well-defined effects of frequency synchronization and at the same time by the domination of low-frequency processes. On the contrary, the MEG of a patient is characterized by a sharp abnormality of frequency synchronization, and also by prevalence of high-frequency quasi-periodic processes. Modification of synchronization effects and dynamics of cross-correlations offer a promising method of detecting pathological abnormalities in brain responses. Comment: 24 pages, 9 figures, 1 table
Physica A: Statistical Mechanics and its Applications 06/2010; · 1.68 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The objectives of the current study were twofold: (i) to investigate the neural precursors of the formation of a subjective preference of facial stimuli, and (ii) to characterize the spatiotemporal brain activity patterns distinguishing between preferred and non-preferred faces. Multivariate EEG signals were recorded while participants made preference decisions, based on approachability, between two faces presented sequentially with unrestricted viewing time; the decision being made after presentation of the second face. The paired faces were similar in their physical properties, emphasizing the role of the subjective experience of the participants in making the decisions. EEG signals were analyzed in terms of event-related-potential (ERP) components and wavelet-based time-frequency-representations (TFR). The behavioural data showed that the presentation order and the exposure duration did not influence preference formation. The EEG data showed three effects. The earliest effect, the sustained posterior ERP positivity for preferred first faces as compared to non-preferred first faces, was found following the onset of the first face, and this was interpreted as the formation of a positive first impression of the first face. The two later effects following the second faces were an increase of frontal theta band oscillations around 500 ms for preferred second faces and of posterior gamma band oscillations around 650 ms for preferred first faces; both of which were interpreted as being related to the formation of a preference. All of these effects occurred well before the moment of conscious decision, thereby suggesting the implicitness of these neurally identifiable components.
[Show abstract][Hide abstract] ABSTRACT: Blink-related ocular activity is a major source of artifacts in electroencephalogram (EEG) data. Independent component analysis (ICA) is a well-known technique for the correction of such ocular artifacts, but one of the limitations of ICA is that the ICs selected for removal contain not only ocular activity but also some EEG activity. Straightforward removal of these ICs might, therefore, lead to a loss of EEG data. In this article a method is proposed to separate blink-related ocular activity from actual EEG by combining ICA with a novel technique, empirical mode decomposition. This combination of two techniques allows for maximizing the retention of EEG data and the selective removal of the eyeblink artifact. The performance of the proposed method is demonstrated with simulated and real data.
[Show abstract][Hide abstract] ABSTRACT: The ability to anticipate forthcoming events has clear evolutionary advantages, and predictive successes or failures often entail significant psychological and physiological consequences. In music perception, the confirmation and violation of expectations are critical to the communication of emotion and aesthetic effects of a composition. Neuroscientific research on musical expectations has focused on harmony. Although harmony is important in Western tonal styles, other musical traditions, emphasizing pitch and melody, have been rather neglected. In this study, we investigated melodic pitch expectations elicited by ecologically valid musical stimuli by drawing together computational, behavioural, and electrophysiological evidence. Unlike rule-based models, our computational model acquires knowledge through unsupervised statistical learning of sequential structure in music and uses this knowledge to estimate the conditional probability (and information content) of musical notes. Unlike previous behavioural paradigms that interrupt a stimulus, we devised a new paradigm for studying auditory expectation without compromising ecological validity. A strong negative correlation was found between the probability of notes predicted by our model and the subjectively perceived degree of expectedness. Our electrophysiological results showed that low-probability notes, as compared to high-probability notes, elicited a larger (i) negative ERP component at a late time period (400-450 ms), (ii) beta band (14-30 Hz) oscillation over the parietal lobe, and (iii) long-range phase synchronization between multiple brain regions. Altogether, the study demonstrated that statistical learning produces information-theoretic descriptions of musical notes that are proportional to their perceived expectedness and are associated with characteristic patterns of neural activity.
[Show abstract][Hide abstract] ABSTRACT: In our earlier study dealing with the analysis of neuromagnetic responses (magnetoencephalograms - MEG) to flickering-color stimuli for a group of control human subjects (9 volunteers) and a patient with photosensitive epilepsy (a 12-year old girl), it was shown that Flicker-Noise Spectroscopy (FNS) was able to identify specific differences in the responses of each organism. The high specificity of individual MEG responses manifested itself in the values of FNS parameters for both chaotic and resonant components of the original signal. The present study applies the FNS cross-correlation function to the analysis of correlations between the MEG responses simultaneously measured at spatially separated points of the human cortex processing the red-blue flickering color stimulus. It is shown that the cross-correlations for control (healthy) subjects are characterized by frequency and phase synchronization at different points of the cortex, with the dynamics of neuromagnetic responses being determined by the low-frequency processes that correspond to normal physiological rhythms. But for the patient, the frequency and phase synchronization breaks down, which is associated with the suppression of cortical regulatory functions when the flickering-color stimulus is applied, and higher frequencies start playing the dominating role. This suggests that the disruption of correlations in the MEG responses is the indicator of pathological changes leading to photosensitive epilepsy, which can be used for developing a method of diagnosing the disease based on the analysis with the FNS cross-correlation function. Comment: 21 pages, 14 figures; submitted to "Laser Physics", 2010, 20