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Aging and Working Memory Performance: Electrophysiological Correlates of High and Low Performing Elderly
Abstract
In this study we investigated age-related changes in WM capacity and their respective ERP correlates. We explicitly addressed the differentiation between high and low performing elderly to identify electrophysiological correlates of successful aging. Therefore, ERP and behavioral data was obtained from 45 young (mean = 22.73 years) and 35 older participants (mean = 68.49 years). Both groups performed a visual-spatial n-back task with two levels of difficulty. Additionally, related neuropsychological tests were administered. Older subjects performed less accurately in both conditions of the n-back task. Older age was additionally associated with a reduced fronto-central positivity (labeled as P200) in the 2-back task and an overall reduced amplitude of the parietal positivity (labeled as P300). The latter shifted to frontal leads in older subjects. Additionally, only in the group of the older participants, increased P200 and decreased parietal P300 amplitudes correlated with performance. Regarding older high and low performers, we observed a clear shift of frontal activity of both ERP components in the group of high performers. High performers additionally performed better in spatial working memory, verbal learning, and fluid intelligence tasks. We conclude, that increasing demands of working memory load are accompanied by a reallocation of resources in both young and older adults. With age, executive control and updating processes (indexed by both ERP components) are diminished or rely on more frontal processes for compensation. However, high performing older adults, who perform comparable to young adults, sustain comparable executive control processes, exceeding pure compensation.
... With aging, the P300 amplitude changes differentially at parietal and frontal sites. At the parietal site, amplitude decreases (Lubitz et al., 2017;McEvoy et al., 2001;Pinal et al., 2015a;Saliasi et al., 2013;Speer & Soldan, 2015;Wild-Wall et al., 2011) or remains stable (Daffner et al., 2010), whereas at the frontal site it increases, leading to a reduction of the predominance of parietal P300 observed in young adults (Fabiani et al., 1998;Fjell & Walhovd, 2001;Friedman et al., 1993Friedman et al., , 1997van Dinteren et al., 2014). This pattern is consistent with the PASA model (Davis et al., 2008), which postulates that the decrease in posterior neural activity observed during aging is coupled with a neural activity increase in anterior areas. ...
... The functional role of this frontal activity increase and the conditions in which it is exhibited remain to be determined. Some studies show that it is linked to lower working memory performance (inefficient neural functioning: Saliasi et al., 2013;Schmitt et al., 2014), whereas others found the opposite pattern (compensation role: Kopp et al., 2014;Lubitz et al., 2017). According to Friedman et al. (1997), the more frontal orientation of the P300 in aging reflects poor frontal functioning. ...
... At the behavioral level, we expected to confirm the classic effects of aging (Gevins et al., 1996;McEvoy et al., 1998;Schneider-Garces et al., 2010;Speer & Soldan, 2015) and set size (Gevins et al., 1996;McEvoy et al., 1998;Schneider-Garces et al., 2010;Speer & Soldan, 2015) on working memory performance and also the classic age-related decline in executive control (see for a review Collette & Salmon, 2014;Craik & Bialystok, 2006Isingrini, 2001;Reuter-Lorenz et al., 2016). At the electrophysiological level, in line with previous studies, we expected that the parietal P300 amplitude would be lower for older than for younger adults and in the 6-item than 2-item memory set (Lubitz et al., 2017;McEvoy et al., 2001;Saliasi et al., 2013;Speer & Soldan, 2015;Wild-Wall et al., 2011). Moreover, consistent with the PASA model (parietal to frontal shift) and with previous studies, we expected to observe a more frontally distributed P300 in older than younger adults (Fabiani et al., 1998;Fjell & Walhovd, 2001;Friedman et al., 1993Friedman et al., , 1997van Dinteren et al., 2014). ...
Executive control could be involved in neural capacity, which corresponds to the modulation of neural activity with increased task difficulty. Thus, by exploring the P300—an electrophysiological correlate of working memory—we examined the role played by executive control in both the age-related decline in working memory and neural capacity in aging. Event-related potentials (ERPs) were recorded while younger and older participants performed a Sternberg task with two set sizes (2 vs. 6 items), allowing us to calculate a neural capacity index. Participants also completed two control tasks (Stroop and 3-back tests), which were used to calculate a composite executive control index. Results indicated that working memory performance decreased with aging and difficulty. At the neural level, results indicated that the P300 amplitude varied with aging and also with task difficulty. In the low difficulty condition, frontal P300 amplitude was higher for older than for younger adults, whereas in the high difficulty condition, the amplitude of frontal and parietal P300 did not differ between both age groups. Results also suggest that task difficulty led to a decrease in parietal amplitude in both age groups and to an increase in frontal amplitude in younger but not older adults. Both executive control and frontal neural capacity mediated the agerelated variance in working memory for older adults. Moreover, executive control mediated the age-related variance in the frontal neural capacity of older adults. Thus, the present study suggests a model for older adults in which executive control deficits with advancing age lead to less efficient frontal recruitment to cope with task difficulty (neural capacity), which in turn has a negative impact on working memory functioning.
... Likewise, connectivity measures for easy task conditions indicate increased connectivity between lateral frontal areas and other networks with increasing age (Gallen et al., 2016), but no difference in connectivity strength between frontal and parietal regions (Heinzel et al., 2017). Similar findings are observed when M/EEG studies are considered (Schwarzkopp et al., 2016;Tran et al., 2016;Lubitz et al., 2017;Morrison et al., 2019;Tagliabue et al., 2019Tagliabue et al., , 2020: Taken together, the findings indicate that components reflecting attentional engagement and maintenance in WM may be enhanced, reduced or similar between age groups, even in the presence of marked behavioral differences. For instance, some EEG studies found decrements in older adults' WM with a concurrent less pronounced (Lubitz et al., 2017) or enhanced fronto-central P200 (Morrison et al., 2019), an ERP component reflecting deployment of attentional resources. ...
... Similar findings are observed when M/EEG studies are considered (Schwarzkopp et al., 2016;Tran et al., 2016;Lubitz et al., 2017;Morrison et al., 2019;Tagliabue et al., 2019Tagliabue et al., , 2020: Taken together, the findings indicate that components reflecting attentional engagement and maintenance in WM may be enhanced, reduced or similar between age groups, even in the presence of marked behavioral differences. For instance, some EEG studies found decrements in older adults' WM with a concurrent less pronounced (Lubitz et al., 2017) or enhanced fronto-central P200 (Morrison et al., 2019), an ERP component reflecting deployment of attentional resources. Additionally, when individuals are presented with different memory loads, older adults might show either similar (Schwarzkopp et al., 2016;Tran et al., 2016) or reduced (Tagliabue et al., 2019(Tagliabue et al., , 2020 load-related modulations of the CDA, an ERP response indexing the amount of items maintained in the WM shortterm storage. ...
... On one hand, dividing individuals (both young and old) in high and low performers may offer a less spurious estimate of age-related neural changes in the utilization of cognitive resources. For instance, in an EEG study by Daffner et al. (2011), low and high performers similarly allocated processing resources with increasing difficulty, regardless of age (see also Lubitz et al., 2017 andMorrison et al., 2019 for more recent EEG studies). Similarly, an fMRI study of Nagel et al. (2009) showed that, when considered altogether, elderly exhibited compromised brain responsivity compared to younger adults. ...
A reduction in cognitive resources has been originally proposed to account for age-related decrements in several cognitive domains. According to this view, aging limits the pool of available cognitive supplies: Compared to younger adults, elderly exhaust the resources more rapidly as task difficulty increases, hence a dramatic performance drop. Neurophysiological indexes (e.g., BOLD response and EEG activity) may be instrumental to quantify the amount of such cognitive resources in the brain and to pinpoint the stage of stimulus processing where the decrement in age-related resources is evident. However, as we discuss in this mini-review, the most recent studies on the neurophysiological markers of age-related changes lack a consistent coupling between neural and behavioral effects, which casts doubt on the advantage of measuring neural indexes to study resource deployment in aging. For instance, in the working memory (WM) domain, recent cross-sectional studies found varying patterns of concurrent age-related brain activity, ranging from equivalent to reduced and increased activations of old with respect to younger adults. In an attempt to reconcile these seemingly inconsistent findings of brain-behavior coupling, we focus on the contribution of confounding sources of variability and propose ways to control for them. Finally, we suggest an alternative perspective to explain age-related effects that implies a qualitative (instead of or along with a quantitative) difference in the deployment of cognitive resources in aging.
... However, while the neurophysiological bases of healthy agingrelated changes in WM functions reflecting the central executive component have extensively been studied in the visual domain ( Daffner et al. , 2011 ;Falkenstein, 2014 , 2018 ;Jonides et al. , 1997 ;Lubitz et al. , 2017 ;McEvoy et al. , 2001 ;Missonnier et al. , 2004 ;West and Bowry, 2005 ;Wild-Wall et al. , 2011 ), they have been overlooked in the auditory domain, favoring tasks mostly addressing storage capacity, such as the Sternberg's task and Delayed Match-to Sample Tasks (DMTS; Chao and Knight, 1997 ;Golob and Starr, 20 0 0 ;Karrasch et al. , 2004 ;Pelosi and Blumhardt, 1999 ;Pratt et al. , 1989 ). Although equivalent visual-verbal and auditory-verbal WM tasks recruit the activity of overlapping brain regions due to the supramodal characteristics of WM, these different modalities are associated with different activity patterns as well ( Rodriguez-Jimenez et al. , 2009 ). ...
... Furthermore, we correlated behavioral indices of the n-back task with frontal theta power differences across workload levels in order to explore the link between performance and central executive activity ( Finnigan and Robertson, 2011 ). According to auditory WM literature and visual n-back task aging studies, we expected to find: (1) A decrease in performance with workload, especially affecting older participants ( Bopp and Verhaeghen, 2020 ); (2) an age-related increase in early sensory ERPs, as a result of placing more weight on the early processing of incoming auditory stimulation, in line with accounts of impaired "sensory gating" ( Chao and Knight, 1997 ); (3) an age-related decrease of late frontal and parietal ERPs, particularly the Sustained Frontal Negativity (SFN), related to sustained auditory attention during item retention in auditory DMTS tasks ( Chao and Knight, 1997 ), and the P3b, related to cognitive resource allocation, among other functions ( Chao and Knight, 1997 ;Polich, 2007 ); (4) a workload-related increase of the SFN, at least in young adults as seen in auditory n-back tasks ( Alain et al. , 2009 ) and DMTS ( Guimond et al. , 2011 ;Lefebvere et al. , 2013 ;Alunni-Menichini et al. , 2014 ); workload effects on the P3b usually show a reduction of this component ( Polich, 2007 ), albeit results in visual and auditory n-back tasks are inconsistent (e.g., Daffner et al. , 2011 ;Gajewski and Falkenstein, 2014 ;Lubitz et al. , 2017 ;Saliasi et al. , 2013 ;Arjona-Valladares et al. , 2021 ); (5) an agerelated decrease and a workload-related increase in frontal theta power, correlating with performance, indexing central executive and memory function ( Cummins and Finnigan, 2007 ;Jensen and Tesche, 2002 ); and (6) considering that older participants may reach supra-capacity levels at high load, finding the task too difficult to continuously apply full cognitive effort ( Gajewski and Falkenstein, 2014 ;Van Snellenberg et al. , 2015 ), we may find the direction of workload effects in late ERPs (SFN and P3b) and theta power measures to be opposite in older (decrease) as compared to younger (increase) participants. ...
... As expected, our behavioral results showed that increasing workload in AWM from 1-to 2-back hinders performance, both in accuracy ( d' ) and reaction times, the Older group being the most affected. This replicates a reliable finding from visual n-back task studies ( Daffner et al. , 2011 ;Falkenstein, 2014 , 2018 ;Jonides et al. , 1997 ;Lubitz et al. , 2017 ;McEvoy et al. , 2001 ;Missonnier et al. , 2004 ;West and Bowry, 2005 ;Wild-Wall et al. , 2011 ), in line with the idea that age-related differences are revealed when the difficulty of the tasks increases ( Hess, 2005 ;Klencklen et al. , 2017 ). AWM studies manipulating memory load in Sternberg type tasks ( Sternberg, 1966 ) also reported effects of aging in performance and electrophysiological as well as fMRI indices ( Chao and Knight, 1997 ;Golob and Starr, 20 0 0 ;Grady et al. , 2008 ;Karrasch et al. , 2004 ;Pelosi and Blumhardt, 1999 ;Pratt et al. , 1989 ). ...
Speech comprehension deficits constitute a major issue for an increasingly aged population, as they may lead older individuals to social isolation. Since conversation requires constant monitoring, updating and selecting information, auditory working memory decline, rather than impoverished hearing acuity, has been suggested a core factor. However, in stark contrast to the visual domain, the neurophysiological mechanisms underlying auditory working memory deficits in healthy aging remain poorly understood, especially those related to on-the-fly information processing under increasing load. Therefore, we investigated the behavioral costs and electrophysiological differences associated with healthy aging and working memory load during continuous auditory processing. We recorded EEG activity from twenty-seven younger (∼25 yo) and twenty-nine older (∼70 yo) participants during their performance on an auditory version of the n-back task with speech syllables and two workload levels (1-back; 2-back). Behavioral measures were analyzed as indices of function; event-related potentials as proxies for sensory and cognitive processes; and theta oscillatory power as a reflection of memory and central executive function. Our results show age-related differences in auditory information processing within a latency range that is consistent with a series of impaired functions, from sensory gating to cognitive resource allocation during constant information updating, especially under high load.
... These results were interpreted as a decreased availability of processing resources and a slowing of stimulus evaluation and categorization during information encoding in working memory. Lubitz et al. (2017) also investigated the effect of aging on working memory with a n-back memory task. Interestingly, authors compared the high and low performing older adults, thus providing insight into the successful aspect of working memory in the older adults. ...
... The P200 amplitude has also been associated with working memory (Bolduc-Teasdale et al., 2019;Finnigan et al., 2011;Gevins et al., 1996;Lubitz et al., 2017;Pinal et al., 2015;Schleepen et al., 2014). Accordingly, the reduced amplitude of the P200 in older adults with TBI can be interpreted as a working memory impairment. ...
... The lower amplitude of the P200 in the TBI group than control group could be interpreted as an overall working memory impairment involved in memory processes per se. This view would be consistent with Lubitz et al. (2017) that show an increased P200 amplitude in high performing older adults in a n-back working memory task. However, neuropsychological results on the test assessing working memory were not significant; older adults with TBI only tended to show lower performances than controls at the Spatial Span test (WMS-III, Wechsler (1997a)). ...
Episodic memory and attention impairments are frequently observed following a traumatic brain injury (TBI). Older adults are more affected than young adults after a TBI, partly because of the age-related neural and memory changes. Neural mechanisms underlying episodic memory deficits in older adults with chronic TBI remain to be investigated. The current study aimed to investigate the impact of TBI in older adults on the neural mechanisms of episodic encoding. Event-related potentials were recorded while 13 participants with mild-to-severe TBI and 14 matched controls were performing an episodic memory task in which the level of organizational strategy was manipulated through three encoding conditions. Participants were explicitly instructed to memorize words without any semantic relationship (Unrelated condition), words semantically related without any given strategies (Spontaneous condition) and words semantically related with provided category labels and organizational strategy (Guided condition). Behavioral performances indicated that older individuals with a TBI were impaired compared to matched controls whatever the condition. The electrophysiological findings showed a reduction of the P200 and LPC components amplitude in the TBI group relative to control group. Moreover, control participants without any neurological history showed a right frontal sustained activity only in the Spontaneous condition, whereas a right frontal asymmetry was observed in participants with chronic TBI whatever the encoding conditions. This was mainly the result of negative left frontal activity. These findings evidence neural dysfunctions underlying attentional and associative processes involved in memory strategies after a TBI sustained at an older age that are consistent with executive functions impairments.
... In general, the common goal of these studies was to ascertain the effect of age in the cortical-evoked responses elicited by tasks requiring WM resources. Within this framework, the most studied task has been the n-back task, which is thought to entail WM-related processes for encoding and temporary storing information and a continuous updating of incoming information, in particular using an easy/ low load vs. difficult/high load condition (e.g., 0-back or 1-back vs. 2back or 3-back [30][31][32][33]). In general, older adults encounter difficulties, especially in high-demanding conditions of the n-back task (2-back or 3back). ...
... With respect to event-related potential (ERP) analyses, three main components have been analyzed: the P1, the N1/N2, and the P200/P300. Typically, P200 components at fronto-central sites showed various latencies, depending on experimental task manipulations, ranging from 170−270 ms [30] to 240−320 ms [33], and are assumed to reflect executive attention [34]. Compared with P200, P300 components at parietal sits revealed more homogeneous temporal intervals, peaking between 300 and 500 ms after target onset (depending on the study). ...
... Compared with P200, P300 components at parietal sits revealed more homogeneous temporal intervals, peaking between 300 and 500 ms after target onset (depending on the study). These two components have been established to reflect updating processes in WM as well as WM load [33]. In general, these studies revealed a significant age effect, showing increased P200 amplitudes in frontal regions [30] and decreased P300 amplitude levels in parietal sites of older adults [30,33], especially when low-performing older adults were considered [32]. ...
Older adults typically show poor performance in tasks assessing working memory (WM), a crucial cognitive mechanism. The present study examined the electrophysiological correlates of a classic complex WM task often used in studies involving older adults, the Categorization Working Memory Span task (CWMS), by means of event-related potentials. Thirty-five healthy, right-handed older adults (64-75 years) were presented the CWMS task while a 38-channel EEG was measured, and the N1, P1, and word recognition potential (RP) were analyzed on four regions of interest (ROIs) of 5 electrodes each. Additionally, late positive components (P200 and P300) were analyzed in midline ROIs of 3 electrodes each. Participants also executed an n-back task (2-back condition) and an objective performance-based task (the Ability to solve Problems in Everyday life [APE]). At a behavioral level, significant correlations were found between the CWMS, the 2-back, and the APE tests. At a physiological level, N1 and word RP showed greater bilateral amplitude in posterior electrodes, but the better the CWMS and the 2-back performance, the greater the RP amplitude on posterior left sites. The CWMS task induced a clear P200 component, but its amplitude was not correlated with participants’ behavioral performance. Altogether, notwithstanding that the bilateral RP pattern elicited by the CWMS is a clear marker of WM processing in older adults, better elderly performers on this complex WM test showed greater left hemisphere dominance to the automatic word RP.
... As previously indicated, patients with fibromyalgia showed enhanced amplitudes of P2 component compared to healthy participants in two spatial regions (frontocentral and parieto-occipital) delimitated by spatial principal component analysis. Although there is still some debate about the significance of this cortical response, it has been argued that the posterior P2 component may represent memory encoding and recoding processing [51], whereas frontocentral P2 seem to be related to executive attention [79,80]. Neuroimaging studies have indicated that a distinctive activation pattern Content courtesy of Springer Nature, terms of use apply. ...
... This fact, together with the generalized compensatory processing here detected in fibromyalgia, could contribute to explain the enhancement of neural indices (frontocental P2 amplitudes) in patients carrying Val/Val genotype of the COMT gene. As it was mentioned, frontal and frontocentral P2 activity has been associated with the activation of executive attention processes [79,80]. Executive attention allows information to be actively maintained and manipulated [99], which makes this subprocess a crucial element for the correct performance in working memory tasks. ...
Recent findings have associated different COMT genotypes with working memory capacity in patients with fibromyalgia. Although it is thought that the COMT gene may influence neural correlates (P2 and P3 ERP components) underlying working memory impairment in this chronic-pain syndrome, it has not yet been explored. Therefore, the aim of the present research was to investigate the potential effect of the COMT gene in fibromyalgia patients on ERP working memory indices (P2 and P3 components). For this purpose, 102 participants (51 patients and 51 healthy control participants) took part in the experiment. Event-related potentials and behavioral responses were recorded while participants performed a spatial n-back task. Participants had to decide if the stimulus coincided or not in the same location as the one presented one (1-back condition) or two (2-back condition) trials before. Genotypes of the COMT gene were determined through a saliva sample from all participants. Present results significantly showed lower working memory performance ( p < 0.05) in patients with fibromyalgia as compared to control participants (higher rate of errors and slower reaction times). At neural level, we found that patients exhibited enhanced frontocentral and parieto-occipital P2 amplitudes compared to control participants ( p < 0.05). Interestingly, we also observed that only fibromyalgia patients carrying the Val/Val genotype of the COMT gene showed higher frontocentral P2 amplitudes than control participants ( p < 0.05). Current results (behavioral outcomes and P2 amplitudes) confirmed the presence of an alteration in working memory functioning in fibromyalgia. The enhancement of frontocentral P2 could be reflecting that these patients would manifest an inefficient way of activating executive attention processes, in carriers of the Val/Val genotype of COMT. To our knowledge, the present findings are the first linking neural indices of working memory dysfunctions and COMT genotypes in fibromyalgia. Applying a subgroup of patient’s strategy based on this genetic marker could be useful to establish more tailored therapeutical approaches.
... As previously indicated, patients with bromyalgia showed enhanced amplitudes of P2 component compared to healthy participants in two spatial regions (frontocentral and parieto-occipital) delimitated by spatial principal component analysis. Although there is still some debate about the signi cance of this cortical response, it has been argued that the posterior P2 component may represent memory encoding and recoding processing [51], whereas frontocentral P2 seem to be related to executive attention [79,80]. Neuroimaging studies have indicated that a distinctive activation pattern involving prefrontal, but also inferior parietal cortices (fronto-parietal memory network), might be underlying, at least partially, working memory impairment in bromyalgia [52]. ...
... This fact, together with the generalised compensatory processing here detected in bromyalgia, could contribute to explain the enhancement of neural indices (frontocental P2 amplitudes) in patients carrying Val/Val genotype of the COMT gene. As it was mentioned, frontal and frontocentral P2 activity has been associated with the activation of executive attention processes [79,80]. Executive attention allows information to be actively maintained and manipulated [99], which makes this sub-process a crucial element for the correct performance in working memory tasks. ...
Recent findings have associated different COMT genotypes with working memory capacity in patients with fibromyalgia. Although it is thought that the COMT gene may influence neural correlates (P2 and P3 ERP components) underlying working memory impairment in this chronic pain syndrome, it has not yet been explored. Therefore, the aim of the present research was to investigate the potential effect of the COMT gene in fibromyalgia patients on ERP working memory indices (P2 and P3 components). For this purpose, 102 participants (51 patients and 51 healthy control participants) took part in the experiment. Event-related potentials and behavioural responses were recorded while participants performed a spatial n-back task. Participants had to decide if the stimulus coincided or not in the same location as the one presented one (1-back condition) or two (2-back condition) trials before. Genotypes of the COMT gene were determined through a saliva sample from all participants. Present results significantly showed lower working memory performance (p < 0.05) in patients with fibromyalgia as compared to control participants (higher rate of errors and slower reaction times). At neural level, we found that patients exhibited enhanced frontocentral and parieto-occipital P2 amplitudes compared to control participants (p < 0.05). Interestingly, we also observed that only fibromyalgia patients carrying the Val/Val genotype of the COMT gene showed higher frontocentral P2 amplitudes than control participants (p < 0.05). Current results (behavioural outcomes and P2 amplitudes) confirmed the presence of an alteration in working memory functioning in fibromyalgia. The enhancement of frontocentral P2 could be reflecting that these patients would manifest an inefficient way of activating executive attention processes, in carriers of the Val/Val genotype of COMT. To our knowledge, the present findings are the first linking neural indices of working memory dysfunctions and COMT genotypes in fibromyalgia. Applying a subgroup of patient’s strategy based on this genetic marker could be useful to establish more tailored therapeutical approaches.
... As previously indicated, patients with bromyalgia showed enhanced amplitudes of P2 component compared to healthy participants in two spatial regions (frontocentral and parieto-occipital) delimitated by spatial principal component analysis. Although there is still some debate about the signi cance of this cortical response, it has been argued that the posterior P2 component may represent memory encoding and recoding processing [51], whereas frontocentral P2 seem to be related to executive attention [79,80]. Neuroimaging studies have indicated that a distinctive activation pattern involving prefrontal, but also inferior parietal cortices (fronto-parietal memory network), might be underlying, at least partially, working memory impairment in bromyalgia [52]. ...
... This fact, together with the generalised compensatory processing here detected in bromyalgia, could contribute to explain the enhancement of neural indices (frontocental P2 amplitudes) in patients carrying Val/Val genotype of the COMT gene. As it was mentioned, frontal and frontocentral P2 activity has been associated with the activation of executive attention processes [79,80]. Executive attention allows information to be actively maintained and manipulated [99], which makes this sub-process a crucial element for the correct performance in working memory tasks. ...
Recent findings have associated different COMT genotypes with working memory capacity in patients with fibromyalgia. Although it is thought that the COMT gene may influence neural correlates (P2 and P3 ERP components) underlying working memory impairment in this chronic pain syndrome, it has not yet been explored. Therefore, the aim of the present research was to investigate the potential effect of the COMT gene in fibromyalgia patients on ERP working memory indices (P2 and P3 components). For this purpose, 102 participants (51 patients and 51 healthy control participants) took part in the experiment. Event-related potentials and behavioural responses were recorded while participants performed a spatial n-back task. Participants had to decide if the stimulus coincided or not in the same location as the one presented one (1-back condition) or two (2-back condition) trials before. Genotypes of the COMT gene were determined through a saliva sample from all participants. Present results significantly showed lower working memory performance (p < 0.05) in patients with fibromyalgia as compared to control participants (higher rate of errors and slower reaction times). At neural level, we found that patients exhibited enhanced frontocentral and parieto-occipital P2 amplitudes compared to control participants (p < 0.05). Interestingly, we also observed that only fibromyalgia patients carrying the Val/Val genotype of the COMT gene showed higher frontocentral P2 amplitudes than control participants (p < 0.05). Current results (behavioural outcomes and P2 amplitudes) confirmed the presence of an alteration in working memory functioning in fibromyalgia. The enhancement of frontocentral P2 could be reflecting that these patients would manifest an inefficient way of activating executive attention processes, in carriers of the Val/Val genotype of COMT. To our knowledge, the present findings are the first linking neural indices of working memory dysfunctions and COMT genotypes in fibromyalgia. Applying a subgroup of patient’s strategy based on this genetic marker could be useful to establish more tailored therapeutical approaches.
... As previously indicated, patients with bromyalgia showed enhanced amplitudes of P2 component compared to healthy participants in two spatial regions (frontocentral and parieto-occipital) delimitated by spatial principal component analysis. Although there is still some debate about the signi cance of this cortical response, it has been argued that the posterior P2 component may represent memory encoding and recoding processing [51], whereas frontocentral P2 seem to be related to executive attention [79,80]. Neuroimaging studies have indicated that a distinctive activation pattern involving prefrontal, but also inferior parietal cortices (fronto-parietal memory network), might be underlying, at least partially, working memory impairment in bromyalgia [52]. ...
... This fact, together with the generalised compensatory processing here detected in bromyalgia, could contribute to explain the enhancement of neural indices (frontocental P2 amplitudes) in patients carrying Val/Val genotype of the COMT gene. As it was mentioned, frontal and frontocentral P2 activity has been associated with the activation of executive attention processes [79,80]. Executive attention allows information to be actively maintained and manipulated [99], which makes this sub-process a crucial element for the correct performance in working memory tasks. ...
Recent findings have associated different COMT genotypes with working memory capacity in patients with fibromyalgia. Although it is thought that the COMT gene may influence neural correlates (P2 and P3 ERP components) underlying this cognitive dysfunction it has not been still explored. 51 patients and 51 healthy control participants took part in this study. Event-related potentials and behavioural responses were recorded while participants performed a spatial n-back task (1-back and 2-back conditions). Genotypes of the COMT gene were determined through a saliva sample from all participants. Present results showed lower working memory performance (higher rate of errors and slower reaction times) in patients with fibromyalgia than in control participants. Temporal dynamics of working memory processing were analysed on P2 and P3 components. We found enhanced frontocentral and parieto-occipital P2 amplitudes for patients as compared to the control group. Interestingly, we also observed a significant influence of COMT gene that was specifically explained by the Val/Val genotype. Thus, patients with fibromyalgia exhibited higher frontocentral P2 amplitudes than control participants, being specifically pronounced for those carrying the Val/Val genotype. Current results (behavioural outcomes and P2 amplitudes) confirmed the presence of an alteration in working memory functioning in fibromyalgia. The enhancement of frontocentral P2 amplitudes might be reflecting an inefficient manner to activate executive attention processes by patients carrying Val/Val genotype of the COMT gene. To our knowledge, the present findings are the first linking neural indices of working memory dysfunctions and COMT genotypes in fibromyalgia. Applying a subgroup of patient’s strategy based on this genetic marker could be useful to establish more tailored therapeutical approaches.
... Thus, ERP has been considered as an important tool for examining the neuronal effects of WM (Scharinger et al., 2017;Zhao et al., 2013). Among many components of ERP, P3 has long been considered to be closely related to WM (Dong et al., 2015;Lubitz et al., 2017). In accordance with the context updating model and resource allocation theory (Gajewski & Falkenstein, 2018;Zhao et al., 2013), P3 reflects processes of detection of stimuli changes, and establishes representations updating and cognitive resources allocation in mind (Polich, 2007;Scharinger et al., 2017). ...
... The amplitudes and latencies of P3a and P3b actually to some extent represent the performance of the WM function (Covey et al., 2018;Pergher et al., 2018;Zhao et al., 2013). Well-performing individuals are allowed to invest less cognitive processing resources and complete faster than underperforming individuals faced with the same task, and they have higher amplitudes and shorter latencies of P3a and P3b correspondingly (Dong et al., 2015;Fjell et al., 2007;Lubitz et al., 2017). Therefore, from a theoretical point of view, the neural effects of WM training would be manifested as significantly increased amplitudes and shortened latencies of P3a and P3b. ...
Background
Recent studies have examined the effect of computerized cognitive training on working memory (WM), but the behavioral and neural effects were uncertain. Also, few studies have explored WM training effects on children using event-related potentials. The purpose of our study was to investigate the effects of WM training in children, including the effects on behavioral performance and neurophysiological outcomes.
Methods
Forty-four healthy children (mean age = 7.76 years, SD = 0.57 years, 18 females) were assigned to the training and control groups. Over 20 training sessions, the training group participated in the computation-span and spatial N-back tasks, whereas the control group joined in normal class activities. They all completed the pre- and post-test evaluation of WM tasks (digit span backwards task and N-back task).
Results
The results showed that WM training led to improved performance in the digit span backwards task and 2-back task of post-test evaluation, shortened P3a and P3b latencies in nontarget trials during the spatial 1-back task, shortened P3a latency in target and nontarget trials, as well as increased P3b amplitude and shortened P3b latency in target trials during the spatial 2-back task.
Conclusions
These results suggested that WM training might enhance children's behavioral performance on WM tasks and brought about neurophysiological changes. This study gives insights into the potential of WM training effects on children's behavioral performance and neurophysiological outcomes.
... The P3, a positive peak that appears with a latency between 250 to 500 ms in the event-related potential (ERP), has been implicated in attention and working memory processes across the lifespan (Van Dinteren et al., 2014). A previous study showed reduced positivity in P3 central-frontal and parietal ERPs in older adults (Lubitz et al., 2017), whereas others demonstrated frontal hyperactivity in P3 coupled with parietal or posterior hypoactivity (Fjell and Walhovd, 2001;Saliasi et al., 2013). Despite the ambiguity in ERP findings, most studies conclude that the abnormal ERP response in older individuals reflects inefficient or compensatory use of neural resources due to frontal cortex dysfunction (Saliasi et al., 2013;Lubitz et al., 2017). ...
... A previous study showed reduced positivity in P3 central-frontal and parietal ERPs in older adults (Lubitz et al., 2017), whereas others demonstrated frontal hyperactivity in P3 coupled with parietal or posterior hypoactivity (Fjell and Walhovd, 2001;Saliasi et al., 2013). Despite the ambiguity in ERP findings, most studies conclude that the abnormal ERP response in older individuals reflects inefficient or compensatory use of neural resources due to frontal cortex dysfunction (Saliasi et al., 2013;Lubitz et al., 2017). Therefore, electrophysiological responses to working memory tasks are convenient measures to test hypotheses related to frontal cortex function, normal cognitive aging, and early neurodegeneration. ...
Event-related potentials (ERPs) offer unparalleled temporal resolution in tracing distinct electrophysiological processes related to normal and pathological cognitive aging. The stability of ERPs in older individuals with a vast range of cognitive ability has not been established. In this test-retest reliability study, 39 older individuals (age 74.10 (5.4) years; 23 (59%) women; 15 non β-amyloid elevated, 16 β-amyloid elevated, 8 cognitively impaired) with scores on the Montreal Cognitive Assessment (MOCA) ranging between 3 and 30 completed a working memory (n-back) test with three levels of difficulty at baseline and 2-week follow-up. The main aim was to evaluate stability of the ERP on grand averaged task effects for both visits in the total sample (n = 39). Secondary aims were to evaluate the effect of age, group (non β-amyloid elevated; β-amyloid elevated, cognitively impaired), cognitive status (MOCA), and task difficulty on ERP reliability. P3 peak amplitude and latency were measured in predetermined channels. P3 peak amplitude at Fz, our main outcome variable, showed excellent reliability in 0-back (intraclass correlation coefficient (ICC), 95% confidence interval = 0.82 (0.67–0.90) and 1-back (ICC = 0.87 (0.76–0.93), however, only fair reliability in 2-back (ICC = 0.53 (0.09–0.75). Reliability of P3 peak latencies was substantially lower, with ICCs ranging between 0.17 for 2-back and 0.54 for 0-back. Generalized linear mixed models showed no confounding effect of age, group, or task difficulty on stability of P3 amplitude and latency of Fz. By contrast, MOCA scores tended to negatively correlate with P3 amplitude of Fz (p = 0.07). We conclude that P3 peak amplitude, and to lesser extent P3 peak latency, provide a stable measure of electrophysiological processes in older individuals. © Copyright © 2020 Devos, Burns, Liao, Ahmadnezhad, Mahnken, Brooks and Gustafson.
... The P3 component is the third positive peak in the ERP waveform that occurs at about or slightly later than 300 ms after stimulus presentation [11]. The P3 is believed to be associated with neural efficiency and cognitive resource allocation during information processing, memory encoding, and updating of information [12,13]. Working memory tasks are widely used in P3 ERP studies across the spectrum of cognitive impairments, as deterioration in working memory is one of the earliest cognitive dysfunctions observed in mild cognitive impairment (MCI) and is a reliable predictor of Alzheimer's disease (AD) [14,15]. ...
Background:
Cognitive reserve may protect against cognitive decline.
Objective:
This cross-sectional study investigated the association between cognitive reserve and physiological measures of cognitive workload in older adults with cognitive impairment.
Methods:
29 older adults with cognitive impairment (age: 75±6, 11 (38%) women, MoCA: 20±7) and 19 with normal cognition (age: 74±6; 11 (58%) women; MoCA: 28±2) completed a working memory test of increasing task demand (0-, 1-, 2-back). Cognitive workload was indexed using amplitude and latency of the P3 event-related potential (ERP) at electrode sites Fz, Cz, and Pz, and changes in pupillary size, converted to an index of cognitive activity (ICA). The Cognitive Reserve Index questionnaire (CRIq) evaluated Education, Work Activity, and Leisure Time as a proxy of cognitive reserve. Linear mixed models evaluated the main effects of cognitive status, CRIq, and the interaction effect of CRIq by cognitive status on ERP and ICA.
Results:
The interaction effect of CRIq total score by cognitive status on P3 ERP and ICA was not significant. However, higher CRIq total scores were associated with lower ICA (p = 0.03). The interaction effects of CRIq subscores showed that Work Activity affected P3 amplitude (p = 0.03) and ICA (p = 0.03) differently between older adults with and without cognitive impairments. Similarly, Education affected ICA (p = 0.02) differently between the two groups. No associations were observed between CRIq and P3 latency.
Conclusion:
Specific components of cognitive reserve affect cognitive workload and neural efficiency differently in older adults with and without cognitive impairments.
... Evidence suggests that a frontal-parietal network involving DLPFC and PPC underlies WM function, integrating information from posterior regions, where mainly storage takes place, and anterior regions, congregating in the DLPFC, where executive processes are located [33]. In event-related potential (ERP) studies, the late positive component (P300) has been consistently associated with WM [34][35][36] in different tasks such as the oddball [36], n-back [37,38], and Go/NoGo tasks [39]. It has multiple cortical and subcortical generators [40], including the DLPFC [41,42], with a posterior component (P3b) reflecting attention and subsequent memory storage processes [43]. ...
Transcranial direct current stimulation (TDCS) is a technique with which neuronal activity, and therefore potentially behavior, is modulated by applying weak electrical currents to the scalp. Application of TDCS to enhance working memory (WM) has shown promising but also contradictory results, and little emphasis has been placed on repeated stimulation protocols, in which effects are expected to be increased. We aimed to characterize potential behavioral and electrophysiological changes induced by TDCS during WM training and evaluate whether repetitive anodal TDCS has a greater modulatory impact on the processes underpinning WM than single-session stimulation. We examined the effects of single-session and repetitive anodal TDCS to the dorsolateral prefrontal cortex (DLPFC), targeting the frontal-parietal network, during a WM task in 20 healthy participants. TDCS had no significant impact on behavioral measures, including reaction time and accuracy. Analyzing the electrophysiological response, the P300 amplitude significantly increased following repetitive anodal TDCS, however, positively correlating with task performance. P300 changes were identified over the parietal cortex, which is known to engage with the frontal cortex during WM processing. These findings support the hypothesis that repetitive anodal TDCS modulates electrophysiological processes underlying WM.
... The P3 is believed to be associated with cognitive resource allocation during information processing, memory encoding, and updating of information [12,13]. ...
Background: Cognitive reserve may protect against cognitive decline. However, its effect on physiological measures of cognitive workload in adults with cognitive impairments is unclear.
Objective: The aim was to determine the association between cognitive reserve and physiological measures of cognitive workload in older adults with and without cognitive impairments.
Methods: 29 older adults with cognitive impairment (age: 75 (6), 11 (38%) women, MOCA scores 20 (7)) and 19 with normal cognition (age: 74 (6); 11 (58%) women; MOCA 28 (2)) completed a working memory test of increasing task demand (0-, 1-, 2-back). Cognitive workload was indexed using amplitude and latency of the P3 event-related potential (ERP) at electrode sites Fz, Cz, and Pz, and changes in pupillary size, converted to an index of cognitive activity (ICA). The Cognitive Reserve Index questionnaire (CRIq) evaluated Education, Work Activity, and Leisure Time as a proxy of cognitive reserve.
Results: Higher CRIq total scores were associated with larger P3 ERP amplitude (p=0.048), independent of cognitive status (p=0.80), task demand (p=0.003), and electrode site (p<0.0001). This relationship was mainly driven by Work Activity (p=0.0005). Higher CRIq total scores also correlated with higher mean ICA (p=0.002), regardless of cognitive status (p=0.29) and task demand (p=0.12). Both Work Activity (p=0.0002) and Leisure Time (p=0.045) impacted ICA. No relationship was found between CRIq and P3 latency.
Conclusion: Cognitive reserve affects cognitive workload and neural efficiency, regardless of cognitive status. Future longitudinal studies should investigate the causal relationship between cognitive reserve and physiological processes of neural efficiency across cognitive aging.
... The P3 is a positive deflection with a peak occurring around 250-500 ms after stimulus onset (Polich and Kok, 1995;Polich, 2007). Its parietal P3b subcomponent is elicited by infrequent but "expected" targets (Verleger et al., 1994), its amplitude is sensitive to probability, i.e., infrequent stimuli, and decreases with habituation and increases with task difficulty (Watter et al., 2001;Bailey et al., 2016;Lubitz et al., 2017;Scharinger et al., 2017;Vilà-Balló et al., 2018). The P3 has also been associated with memory engagement (Azizian and Polich, 2007). ...
Our brains are often under pressure to process a continuous flow of information in a short time, therefore facing a constantly increasing demand for cognitive resources. Recent studies have highlighted that a lasting improvement of cognitive functions may be achieved by exploiting plasticity, i.e., the brain’s ability to adapt to the ever-changing cognitive demands imposed by the environment. Transcranial direct current stimulation (tDCS), when combined with cognitive training, can promote plasticity, amplify training gains and their maintenance over time. The availability of low-cost wearable devices has made these approaches more feasible, albeit the effectiveness of combined training regimens is still unclear. To quantify the effectiveness of such protocols, many researchers have focused on behavioral measures such as accuracy or reaction time. These variables only return a global, non-specific picture of the underlying cognitive process. Electrophysiology instead has the finer grained resolution required to shed new light on the time course of the events underpinning processes critical to cognitive control, and if and how these processes are modulated by concurrent tDCS. To the best of our knowledge, research in this direction is still very limited. We investigate the electrophysiological correlates of combined 3-day working memory training and non-invasive brain stimulation in young adults. We focus on event-related potentials (ERPs), instead of other features such as oscillations or connectivity, because components can be measured on as little as one electrode. ERP components are, therefore, well suited for use with home devices, usually equipped with a limited number of recording channels. We consider short-, mid-, and long-latency components typically elicited by working memory tasks and assess if and how the amplitude of these components are modulated by the combined training regimen. We found no significant effects of tDCS either behaviorally or in brain activity, as measured by ERPs. We concluded that either tDCS was ineffective (because of the specific protocol or the sample under consideration, i.e., young adults) or brain-related changes, if present, were too subtle. Therefore, we suggest that other measures of brain activity may be more appropriate/sensitive to training- and/or tDCS-induced modulations, such as network connectivity, especially in young adults.
... Although the functional significance of P3 is still not precisely known, many studies have suggested that P3 observed in WM tasks might reflect the updating of WM 40,42,49 . At the same time, P3 has been also shown to be sensitive to normal aging 50 , and age-related reductions in P3 amplitude have been reported by many WM studies [51][52][53] . Consistent with the literature, we found that P3 amplitude was not significantly modulated by the WM task (i.e., the main effect of Task was not observed) at the baseline session for participants in either group. ...
Working memory (WM) is a fundamental cognitive function that typically declines with age. Previous studies have shown that targeted WM training has the potential to improve WM performance in older adults. In the present study, we investigated whether a multi-domain cognitive training program that was not designed to specifically target WM could improve the behavioral performance and affect the neural activity during WM retrieval in healthy older adults. We assigned healthy older participants (70–78 years old) from a local community into a training group who completed a 3-month multi-domain cognitive training and a control group who only attended health education lectures during the same period. Behavioral and electroencephalography (EEG) data were recorded from participants while performing an untrained delayed match or non-match to category task and a control task at a pre-training baseline session and a post-training follow-up session. Behaviorally, we found that participants in the training group showed a trend toward greater WM performance gains than participants in the control group. Event-related potential (ERP) results suggest that the task-related modulation of P3 during WM retrieval was significantly enhanced at the follow-up session compared with the baseline session, and importantly, this enhancement of P3 modulation was only significant in the training group. Furthermore, no training-related effects were observed for the P2 or N2 component during WM retrieval. These results suggest that the multi-domain cognitive training program that was not designed to specifically target WM is a promising approach to improve WM performance in older adults, and that training-related gains in performance are likely mediated by an enhanced modulation of P3 which might reflect the process of WM updating.
... Similarly, when comparing healthy older people with adults with MCI, a positive correlation between performance and LPC amplitude was observed in the healthy group while this relation was absent in MCI patients 38 . Similarly, P200 has also been used as a distinctive feature between younger and older adults 34,35,44 , as well as between healthy and pathological aging 38 . ...
The world population is rapidly aging, bringing together the necessity to better understand the advancing age. This characterization may be used to aid early diagnosis and to guide individually-tailored interventions. While some event-related potential (ERP) components, such as the P300 and late positive complex (LPC), have been associated with fluid intelligence (Gf) in young population; little is known whether these associations hold for older people. Therefore, the main goal of this study was to assess whether these ERP components are associated with Gf in the elderly. Fifty-seven older adults performed a continuous performance task (CPT) and a visual oddball paradigm while EEG was recorded. Participants were divided into two groups, according to their performance in the Raven’s Advanced Progressive Matrices test: high-performance (HP) and low-performance (LP). Results showed that the HP group, compared to the LP group, had higher LPC amplitudes in the CPT and shorter P300 latencies in the oddball task, highlighting the role of ERP components as a potential electrophysiological proxy of Gf abilities in the elderly.
... One possibility is that working memory capacity diminishes with age. 40,41 Less capacity might not allow the older participants to remember the order of the landmarks along the route, and thus it could be difficult to recall during testing trials. Given that our spatial environment was fairly small (only 3 landmarks) and participants were allowed multiple training trials, working memory load was relatively light during our task. ...
Daily life requires accurate navigation, and thus better understanding of aging on navigational abilities is critical. Importantly, the use of spatial properties by older and younger adults remains unclear. During this study, younger and older human adults were presented with a virtual environment in which they had to navigate a series of hallways. The hallways provided 2 general types of spatial information: geometric, which included distance and directional turns along a learned route, and featural, which included landmarks situated along the route. To investigate how participants used these different cue types, geometric and/or landmark information was manipulated during testing trials. Data from 40 younger (20 women) and 40 older (20 women) adults were analyzed. Our findings suggest that (1) both younger and older adults relied mostly on landmarks to find their way, and (2) younger adults were better able to adapt to spatial changes to the environment compared with older adults.
... Third, we hypothesized that old high performers should show enhanced processing efficiency as reflected in increased amplitudes of the pre-target CNV and/or the targetlocked P2/N2 complex, especially with increasing task difficulty, where the executive demands are high. This hypothesis was derived from previous results from our and other labs showing enlarged ERPs associated with superior performance in older age both in cross-sectional and randomized controlled studies (De Sanctis et al., 2009;Ga al and Czigler, 2018;, 2015a, 2018a2018b;Getzmann et al., 2013;Küper et al., 2017;Lubitz et al., 2017;Olfers and Band, 2018;Th€ ones et al., 2018;Wild-Wall et al., 2007. ...
Susceptibility to interference increases with age but there is large inter-individual variability in interference control in older adults due to a number of biological and environmental factors. The present study aims at analyzing behavior and ERPs in a Stroop interference task with increasing difficulty in a sample of 246 young, middle-aged and healthy old participants. The old age group was divided into three subgroups based on performance scores. The results show a gradual performance reduction with increasing age and task difficulty. However, old high performers reached a performance level comparable to middle-aged subjects. The contingent negative variation (CNV) reflecting preparation and proactive task control and the target-locked P2/N2 complex associated with retrieval and implementation of S-R mappings during reactive task control were larger in the old high than low performers and similar to middle-aged or even young participants. High performance was limited to executive control tasks, while other cognitive functions were less affected. In addition, high performance was associated with higher level of education, usage of foreign languages and higher IQ. Thus, the performance differences in old age were discussed in the framework of cognitive reserve that constitutes individual differences in neural networks underlying task performance.
... 26 The verbal fluency test depends on the proper functioning of working memory. A study 27 found that P300 amplitude in adult and elderly individuals varied with the efficiency of working memory. Advanced P300 activity was found at the frontal electrode of participants while working memory was being used, unlike younger individuals, in whom greater posterior activation was found. ...
Objective:
to analyze the relationship between cognitive processing, language and verbal fluency among elderly individuals seen by primary healthcare services located in a city in the interior of São Paulo, Brazil.
Methods:
a cross-sectional study with a quantitative method was conducted. A total of 149 elderly individuals were assessed through previously scheduled interviews. Data collection included a questionnaire on sociodemographic data and the Addenbrooke's Cognitive Examination - Revised (ACE-R). Cognitive processing (P300) was assessed using a device that captures potentials elicited in auditory tasks. Descriptive analysis and Spearman's correlation were performed with the level of significance established at 5%.
Results:
a negative correlation was found between language and P300 latency, while a positive correlation was found between verbal fluency and P300 amplitude. Comprehension and naming tasks showed a negative correlation with latency. The repetition task revealed a positive correlation with P300 amplitude.
Conclusion:
although more extensive testing is needed, these findings suggest that language correlates with P300 latency, whereas verbal fluency correlates with P300 amplitude.
... Working memory (WM) refers to the components responsible for maintain temporally a limited amount of information in an available state to allow the processing of ongoing information (Cowan, 2017). WM performance declines markedly with ageing, and this has been associated with abnormalities on the frontoparietal networks involved in WM, as well as neuromodulatory (dopamine) and neuroanatomical alterations (Bäckman et al., 2017(Bäckman et al., , 2010Lubitz et al., 2017;Park and Reuter-Lorenz, 2009;Raz, 2005;Rottschy et al., 2012;Salthouse, 1990). This reduction in WM capacity in older adults, along with a decrease in processing speed, seem to underlie age-related cognitive decline (Braver and West, 2008), primarily because WM is associated with higher-order cognitive functions (Unsworth et al., 2005), including reasoning (Shakeel and Goghari, 2017), reading (Just and Carpenter, 1992), prospective memory (Bisiacchi et al., 2008), processing speed (Diamond et al., 1999), attention (West, 1999), perceptual organization (Ko et al., 2014), and general language (Kemper et al., 2004). ...
The objective of this meta-analytic review was to systematically assess the effects of working memory training on healthy older adults. We identified 552 entries, of which 27 experiments met our inclusion criteria. The final database included 1130 participants. Near- and far-transfer effects were analysed with measures of short-term memory, working memory, and reasoning. Small significant and long-lasting transfer gains were observed in working memory tasks. Effects on reasoning was very small and only marginally significant. The effects of working memory training on both near and far transfer in older adults were moderated by the type of training tasks; the adopted outcome measures; the training duration; and the total number of training hours. In this review we provide an updated review of the literature in the field by carrying out a robust multi-level meta-analysis focused exclusively on WMT in healthy older adults. Recommendations for future research are suggested.
... Moreover, we found that the high-performers utilized greater neural sources in the PFC, especially at the left side, than the low-performers did. The phenomenon of frontal over-recruitment in our current study may be in accord with the compensation hypothesis between high-and low-performing older adults in terms of memory tasks (Cabeza et al., 2002;Lubitz et al., 2017). There were similar findings in the previous studies. ...
Inhibition, the ability to suppress irrelevant information, thoughts or movements, is crucial for humans to perform context-appropriate behaviors. It was suggested that declined cognitive performance in older adults might be attributed to inhibitory deficiencies. Although previous studies have shown an age-associated reduction in inhibitory ability, the understanding regarding its cortical spatiotemporal maps remained limited. Thus, we used a whole-head magnetoencephalography (MEG) to elucidate the age effects on response inhibition, and to explore the brain activation differences in high- and low-performing seniors. We recruited 22 younger and 22 older adults to participate in the visual Go/No-go task. Both behavioral performance and neuromagnetic responses to No-go stimuli were analyzed. The behavioral results showed that the older adults made more false alarm (FA) errors than the younger adults did. The MEG results showed that the seniors exhibited declined cortical activities in middle temporal gyrus (MTG) and delayed activation in MTG, prefrontal cortex (PFC) and pre-supplementary motor area (pre-SMA). Furthermore, among the older adults, more recruitment of the left PFC was found in the high-performers than in the lower-performers. In conclusion, age-related deficiencies in response inhibition were observed in both behavioral performance and neurophysiological measurement. Our results also suggested that frontal recruitment plays a compensatory role in successful inhibition.
... In n-back tasks, N200 has been interpreted as reflecting match/mismatch processes between the presented stimulus and the representation currently held in memory (see Folstein & Van Petten, 2008, for a detailed review). The amplitude differences of the P200 have been related to higher working memory demands, understanding P200 as a marker for executive attention (Engle, 2002;Lubitz, Niedeggen, & Feser, 2017;Zhao, Zhou, & Fu, 2013). In addition, the amplitude of P300 (the most studied component) tends to decrease with increasing working memory load (Chen, Mitra, & Schlaghecken, 2008;Dong, Reder, Yao, Liu, & Chen, 2015;Scharinger, Soutschek, Schubert, & Gerjets, 2015). ...
It has been generally accepted that skipping breakfast adversely affects cognition, mainly disturbing the attentional processes. However, the effects of short-term fasting upon brain functioning are still unclear. We aimed to evaluate the effect of skipping breakfast on cognitive processing by studying the electrical brain activity of young healthy individuals while performing several working memory tasks. Accordingly, the behavioral results and event-related brain potentials (ERPs) of 20 healthy university students (10 males) were obtained and compared through analysis of variances (ANOVAs), during the performance of three n-back working memory (WM) tasks in two morning sessions on both normal (after breakfast) and 12-hour fasting conditions. Significantly fewer correct responses were achieved during fasting, mainly affecting the higher WM load task. In addition, there were prolonged reaction times with increased task difficulty, regardless of breakfast intake. ERP showed a significant voltage decrement for N200 and P300 during fasting, while the amplitude of P200 notably increased. The results suggest skipping breakfast disturbs earlier cognitive processing steps, particularly attention allocation, early decoding in working memory, and stimulus evaluation, and this effect increases with task difficulty.
Вірус COVID-19, що заразив мільйони людей у всьому світі, викликає різноманітні проблеми,включаючи психіатричні, економічні, освітні та медичні. У багатьох дослідженнях повідомлялося, що COVID-19 вражає судини, переважно мікросудини, пошкоджуючи мікроцеркуляторне русло органів. Головний мозокне виключення і це проявляється деградацією функцій останнього.Найбільш вразливою групою, з вищим ризиком ускладнень, для даної інфекції є люди похилого віку. Саметому, зокрема методи когнітивної реабілітації для даної категорії осіб є дуже актуальними. Одним із такихметодів, може бути нейробіозворотний тренінг (НБТ). НБТ- це неінвазивний, безпечний та ефективний методрегуляції функціонального стану мозку. Зараз НБТ широко використовується для профілактики й реабілітаціїзахворювань мозку та покращення виконавчих функцій людини і став важливим напрямком досліджень вусьому світі.Із нашого попереднього експерименту застосування НБТ для категорії осіб похилого віку, отрималирезультати, що демонструють скорочення латентності та збільшення амплітуди Р300, що проявлялось упокращенні виконавчих функцій.У даному дослідженні НБТ ми перевірили чи впливає COVID-19 на когнітивні функції. Ми зібрали сигналиелектроенцефалограми (ЕЕГ) на основі P300 та відповіді Монреальського когнітивного тесту (МоСА) від 26суб’єктів в період від 2 до 6 місяців після інфікування COVID-19. На основі аналізу t-критерію, було помічено,що існує значуща різниця між тестовими групами до та після застосування тренінгу, порівняно із групоюконтролю за результатами МоСА.З іншого боку, статистична значущість Р300 не відображає різниці для обох груп, хоч візуально різницяпомітна. Причиною може бути мала кількість суб’єктів.
Obstacle crossing requires visuospatial working memory to guide the trailing leg trajectory when vision in unavailable. Visuospatial working memory, as assessed with neuropsychological tests, declines with age, however, this remains to be investigated functionally in obstacle crossing. There is also evidence that visuospatial encoding during a secondary task interferes with balance control during stepping and walking in older people. Here, we studied the interaction effects of age by delay (study 1) and age by secondary visuospatial task (study 2) conditions on obstacle clearance in a visuospatial working memory -guided obstacle crossing task. Healthy young adults aged 19 to 36 years (n = 20 in study 1 and n = 17 in study 2) and healthy older adults aged 66 to 83 years (n = 29 in study 1 and n = 21 in study 2) were instructed to step over an obstacle with their leading leg and straddle it for a delay period before completing the crossing with their trailing leg. In study 1, two obstacle height conditions (12 cm, 18 cm) and two delay durations (20 s, 60 s) were presented in random order. In study 2, participants were required to attend to either no secondary task (control), a visuospatial secondary (star movement) task, or a nonspatial secondary (arithmetic) task, while straddling the obstacle for a delay duration of 20 s, at obstacle heights of 12 cm and 18 cm, randomly presented. Trailing leg kinematics (mean and variability of maximum toe clearance over the obstacle) were determined via motion capture. There were no statistically significant age by delay or age by secondary task interactions. In study 1, toe clearance variability was significantly greater in young adults and increased with increasing delay duration in both groups. In study 2, compared with the control condition, toe clearance variability was significantly greater in the non-spatial secondary task condition but not in the visuospatial condition. Contrary to our hypotheses, these findings suggest that young and older adults alike can store an obstacle representation via visuospatial working memory for durations of at least 60 s and use this information to safely scale their trailing leg over an obstacle. However, the increase in trailing leg toe clearance variability with delay duration suggests that obstacle representation starts to deteriorate even within the first 20 s regardless of age. The finding that undertaking a concurrent arithmetic task impaired visuospatial working memory-guided obstacle clearance suggests a potential increased risk of tripping during obstacle crossing while dual-tasking in both young and older people.
Previous studies found that trust violations impaired the ability of working memory (WM) updating, however, these studies did not consider the emotional context in the WM updating. Individuals who experience trust violations have the characteristics of negative bias and enhanced negative emotion. Thus it is necessary to explore how emotional contexts moderate the relationship between trust violations and WM updating. In this study, the trust game was used to manipulate trust violations. Fifty-three participants performed the emotional two-back task while event-related potentials were recorded. Results showed that compared to the control group, the violation group had smaller P2 and P3 amplitudes both in emotional and nonemotional contexts and larger N2 amplitudes in the emotional contexts. There were no significant differences between the two groups on the behavioral data. These results suggest that trust violations result in the inefficient allocation of attention in the early attention (P2) and updating maintenance stages (P3) regardless of the emotional type of the material. Trust violations also improve the abilities of response inhibition, conflict monitoring, or sequential match (N2) when processing emotional material, which may play a compensatory role to maintain a level of behavioral performance comparable to the control group. Together, trust violations affect the sub-processes underlying emotional WM updating differently, and these influences are not valence specific.
Background
Although growing evidence links beta-amyloid (Aβ) and neuronal hyperexcitability in preclinical mouse models of Alzheimer’s disease (AD), a similar association in humans is yet to be established. The first aim of the study was to determine the association between elevated Aβ (Aβ+) and cognitive processes measured by the P3 event-related potential (ERP) in cognitively normal (CN) older adults. The second aim was to compare the event-related power between CNAβ+ and CNAβ−.
Methods
Seventeen CNAβ+ participants (age: 73 ± 5, 11 females, Montreal Cognitive Assessment [MoCA] score 26 ± 2) and 17 CNAβ- participants group-matched for age, sex, and MOCA completed a working memory task ( n -back with n = 0, 1, 2) test while wearing a 256-channel electro-encephalography net. P3 peak amplitude and latency of the target, nontarget and task difference effect (nontarget−target), and event-related power in the delta, theta, alpha, and beta bands, extracted from Fz, Cz, and Pz, were compared between groups using linear mixed models. P3 amplitude of the task difference effect at Fz and event-related power in the delta band were considered main outcomes. Correlations of mean Aβ standard uptake value ratios (SUVR) using positron emission tomography with P3 amplitude and latency of the task difference effect were analyzed using Pearson Correlation Coefficient r .
Results
The P3 peak amplitude of the task difference effect at Fz was lower in the CNAβ+ group ( P = 0.048). Similarly, power was lower in the delta band for nontargets at Fz in the CNAβ+ participants ( P = 0.04). The CNAβ+ participants also demonstrated higher theta and alpha power in channels at Cz and Pz, but no changes in P3 ERP. Strong correlations were found between the mean Aβ SUVR and the latency of the 1-back ( r = − 0.69; P = 0.003) and 2-back ( r = − 0.69; P = 0.004) of the task difference effect at channel Fz in the CNAβ+ group.
Conclusions
Our data suggest that the elevated amyloid in cognitively normal older adults is associated with neuronal hyperexcitability. The decreased P3 task difference likely reflects early impairments in working memory processes. Further research is warranted to determine the validity of ERP in predicting clinical, neurobiological, and functional manifestations of AD.
Background
The changes in electroencephalogram (EEG) signals that reflect the changes in physiological structure, cognitive functions, and activities have been observed in healthy aging adults. It is unknown that when the brain aging initiates and whether these age-related alterations can be associated with incipient neurodegenerative diseases in healthy elderly individuals.
Materials and methods
We employed feature extraction and classification methods to classify and compare the EEG signals of middle-aged and elderly age groups. This study included 20 healthy middle-aged and 20 healthy elderly subjects. The EEG signals were recorded during a resting state (eyes- open and eyes-closed) and during a working memory (WM) task using eight electrodes. The minimum redundancy maximum relevance technique was employed in the selection of the optimal feature. Four classification methods, including decision tree, support vector machine, Naïve Bayes, and K-nearest neighbor, were used to distinguish the elderly age group from the middle-aged group based on their EEG signals.
Results
In the resting state, a good correlation was observed among absolute power delta and theta bands and aging, whereas between beta absolute power and aging, a WM task correlation was observed. The results also indicated that the mean frequency and absolute power might be useful for the prediction and classification of EEG signals in aging individuals. Furthermore, the use of the decision tree method in a WM task state distinguished the elderly group from the young group with an accuracy of 87.5%.
Conclusions
Working memory could play a vital role in the optimization of classification of EEG signals in aging and discrimination of age-related issues associated with neurodegeneration.
Cognitive impairment in older adults is a rapidly growing public health concern as the elderly population dramatically grows worldwide. While it is generally assumed that cognitive deficits in older adults are associated with reduced brain flexibility, quantitative evidence has been lacking. Here, we investigate brain flexibility in healthy older adults (ages 60-85) using a novel Bayesian switching dynamical system algorithm and ultrafast temporal resolution (490 msec) whole-brain fMRI data during performance of a Sternberg working memory task. We identify latent brain states and characterize their dynamic temporal properties, including state transitions, associated with encoding, maintenance, and retrieval. Crucially, we demonstrate that brain inflexibility is associated with slower and more fragmented transitions between latent brain states, and that brain inflexibility mediates the relation between age and cognitive inflexibility. Our study provides a novel neurocomputational framework for investigating latent dynamic circuit processes underlying brain flexibility and cognition in the context of aging.
The present research reports on the effects of age and situation awareness (SA) on the neural processing of auditory tone stimuli presented during a simulated flight experiment to understand how pilots integrate auditory information into their mental models. Understanding the neuro-cognitive processes involved in transforming physical auditory stimuli into cognitive representations is important in the study of aviation psychology as a great deal of information about the environment that pilots receive and use to manage their flight is auditory (e.g., radio communication). Electroencephalogram (EEG) data was collected while 51 pilots conducted a one-hour flight in a Cessna 172 full-scale simulator and were presented with auditory tones. Markers were simultaneously added to the EEG data to reflect the onset of each tone and the pilot button response they were tasked with. Grand average event-related potentials (ERPs) related to the auditory tones compared neural responses for both the older (51+ years) and younger (<51 years) pilot groups. The relationship of age to accuracy of SA models was also investigated by indexing pilot mental models of the relevant environment. Findings showed that auditory information is not always well-integrated into SA models, and this was particularly true for older pilots. Furthermore, changes in how auditory information is processed in the brain may contribute to the negative age-effects seen in pilot SA. This research is important in informing efforts to enhance safety in general aviation. Effective strategies to improve pilot SA may include visual technologies to augment the auditory information available to pilots.
Objective
This study investigated the relationship between neural activities and retinal structures associated with working memory (WM) in older adults with mild cognitive impairment (MCI).
Methods
Eleven older adults with MCI and 29 healthy controls (60 to 73 years old) were tested. All participants underwent an event-related potential (ERP) recording while performing the two-back memory task. The Optical coherence tomography angiography (OCT-A) was administered to examine the perfusion and vessel density in the retina.
Results
Results showed that WM performance in the MCI group was negatively associated with ERP latencies in central parietal regions (CP6 and CP8) (ps< 0.05). The left nasal vessel and perfusion den- sities were negatively correlated with the latencies in these two central parietal regions and positively related to WM performance only in the MCI group (ps< 0.05).
Conclusion
The findings on WM, central parietal brain activity, and left nasal vessel and perfusion densities in the retina help us gain a better understanding of the neural and retinal underpinnings of WM in relation to MCI.
Background
It is well-documented that heroin users demonstrate aberrant emotion-processing abilities. However, the mechanism by which heroin users process emotional information after it has captured their attention and entered their working memory is unclear.
Objectives
A modified emotional 2-back task was used to examine whether heroin abstainers demonstrate specific bias patterns in updating emotional stimuli in their working memory.
Methods
In total, 26 male heroin abstainers and 29 healthy controls were asked to identify whether the current picture was the same as a picture that had appeared two trials earlier, while behavioral data and electroencephalogram data were collected.
Results
Contrary to predictions, the heroin abstainers and healthy controls demonstrated a similar pattern of P300 activity in response to emotional stimuli with no between-group differences in accuracy or reaction time. More specifically, the P300 amplitudes were larger for negative pictures than for positive and neutral pictures. Surprisingly, we found larger P300 amplitudes at Fz electrodes than at Cz and Pz electrodes in the control group, whereas there was no significant difference at midline electrodes in the heroin abstainers.
Conclusions/Importance
Although subtle differences may exist in attentional engagement toward incoming emotional stimulus between two groups, the similar P300 pattern may indicate partial preservation of emotional working memory capacity associated with adaptive emotion regulation in heroin abstainers. These results deepen our understanding of the emotion regulation impairments associated with chronic drug use.
Старість передбачає істотні фізіологічні і психічні зміни. Особливого значення в процесі старіння набувають зміни вищої нервової діяльності, що супроводжуються порушенням вищих психічних функцій різного ступеня важкості та зниженим рівнем стійкості до стресу.
Відомі різні спроби поліпшити когнітивні функції у літніх людей. Одним із перспективних напрямків в області психологічної корекції є тренінг з використанням нейробіологічного зворотного зв’язку.
Викликані потенціали є об'єктивними показниками стану когнітивних функцій і можуть служити для вивчення їх порушень. Компонентом когнітивних викликаних потенціалів (КВП) є позитивна хвиля. Параметрами що її характеризують є латентність Р3 (мс) та амплітуда N2-P3 (мкВ). Вважається, що цей компонент найбільш тісно пов'язаний з когнітивними процесами сприйняття, уваги, пам’яті. Мета нашого дослідження – виявити зміни у КВП перед й після застосуванням нейробіозворотного тренінгу (НБТ).
У дослідженні брало участь 32 жінок похилого віку, з котрих сформовано дві групи по 16 осіб «експерементальну» й «плацебо». Експерементальна група брала участь у 15 сеансах НБТ. Представники групи плацебо вважали, що брали участь у тренінгу, але це була симуляція.
В результаті дослідження встановлено значуще скорочення латентності та збільшення амплітуди у осіб експериментальної групи.
Background:
Binge drinking is a pattern of alcohol intake characterized by excessive and intermittent alcohol consumption over a very short period of time that is more used during adolescence. We aim to compare the lasting effects of a chronic-moderate vs. this intermittent-excessive way of alcohol intake during adolescence in spatial memory and in the expression of glutamatergic receptors and GSK3β activity.
Methods:
Adolescent male Wistar rats were given ethanol/saline i.p. injections in four different groups: High-I (4 g/kg of a 25% (vol/vol) every 3 days), Low-I (1 g/kg of a 5% (vol/vol) every 3 days), M (0.3 g/kg of a 2.5% (vol/vol) daily) and Control (C, sterile isotonic saline daily). Rats received ethanol for up to five 3-day cycles. Spatial memory was measured by spontaneous alternation in the Y-Maze. Gene and protein expression of hippocampal proteins were also analysed.
Results:
Both high- and low-intermittent ethanol administration produced spatial memory impairment and changes in glutamatergic receptors gene expression were observed regardless of the pattern of exposure. High doses of intermittent alcohol administration produced an increase of phosphorylation of GSK3β Ser9. Moreover, moderate alcohol administration produced a down-regulation of the AMPAR 2/3 ratio despite lack of spatial memory deficits.
Conclusions:
Excessive and intermittent ethanol exposure during adolescence impaired the spatial memory processes during adulthood regardless of the amount of alcohol administered. Moreover, chronic-moderate and intermittent pattern induced changes in the expression of glutamatergic receptors. In addition, high-intermittent ethanol exposure during adolescence inactivated GSK3β by increasing its phosphorylation in Ser9.
We investigated whether P300-ERP and cognitive test performance differ for age, sex, and education in two groups of healthy elderly, and verified whether any correlations exist between P300 amplitude and latency and gray matter volume using whole brain voxel-by-voxel-based mapping, controlling for age, education, sex and Total Intracranial Volume (TIV). We used 32 channel electroencephalograms (EEG) to record the P300 responses and 3T Magnetic Resonance Imaging (MRI) to determine gray matter volume. We recruited 36 native-Dutch speaking healthy older subjects, equally divided in two sub-groups of 52–64 and 65–76 years old, administered a battery of cognitive tests and recorded their demographics, EEGs and task performance; additionally, 16 adults from the second sub-group underwent an MRI scan. We found significant differences between age groups in their cognitive tests performance, P300 amplitudes for the frontal and parietal electrodes for the most difficult task, and P300 latencies for frontal, central and parietal electrodes for all three tasks difficulty levels. Interesting, sex and education affected cognitive and P300 results. Higher education was related to higher accuracy, and P300 amplitudes and shorter latencies. Moreover, females exhibited higher P300 amplitudes and shorter latencies, and better cognitive tasks performance compared to males. Additionally, for the 16 adults underwent to MRI scan, we found positive correlations between P300 characteristics in frontal, central and parietal areas and gray matter volume, controlling for demographic variables and TIV, but also showing that age, sex, and education correlate with gray matter volume. These findings provide support that age, sex, and education affect an individual’s cognitive, neurophysiological and structural characteristics, and therefore motivate the need to further investigate these in relation to P300 responses and gray matter volume in healthy elderly.
The ability to temporarily store and manipulate information in working memory is a hallmark of human intelligence and differs considerably across individuals, but the structural brain correlates underlying these differences in working memory capacity (WMC) are only poorly understood. In two separate studies, diffusion MRI data and WMC scores were collected for 70 and 109 healthy individuals. Using a combination of probabilistic tractography and network analysis of the white matter tracts, we examined whether structural brain network properties were predictive of individual WMC. Converging evidence from both studies showed that lateral prefrontal cortex and posterior parietal cortex of high-capacity individuals are more densely connected compared with low-capacity individuals. Importantly, our network approach was further able to dissociate putative functional roles associated with two different pathways connecting frontal and parietal regions: a corticocortical pathway and a subcortical pathway. In Study 1, where participants were required to maintain and update working memory items, the connectivity of the direct and indirect pathway was predictive of WMC. In contrast, in Study 2, where participants were required to maintain working memory items without updating, only the connectivity of the direct pathway was predictive of individual WMC. Our results suggest an important dissociation in the circuitry connecting frontal and parietal regions, where direct frontoparietal connections might support storage and maintenance, whereas subcortically mediated connections support the flexible updating of working memory content.
It is well known that working memory is one of the most vulnerable cognitive functions in elderly. However, little is known about the neuronal underpinnings and temporal dynamics of working memory mechanisms in healthy aging which are necessary to understand the age-related changes. To this end, 36 young and 36 old healthy individuals performed a 2-back task and a 0-back control task, while the electroencephalogram (EEG) was recorded. Participants were instructed to press a response key whenever a target appeared and not to respond in case of nontargets. Expectedly, older participants showed considerably slower RTs and significantly higher rates of omitted targets and false alarms than young participants in the 2-back task, whereas no age-group difference in detection rate was found in the 0-back task. From the EEG event-related potentials as well as time-frequency plots were computed. The ERPs showed a general delay of the frontocentral N2, and an attenuation and delay of both the P3a and P3b in older versus younger adults. Importantly, the frontal P3a was reduced in older adults in the 2-back task. Time-frequency decomposition revealed consistently lower power in frontal theta (6 Hz) and parietal alpha (9–11 Hz) frequency range in older versus younger adults whereas no age-related differences were found in the delta frequency range. Task unspecific reduction of posterior alpha in elderly was paralleled by a reduction of the P3b. In contrast, the older adults had a strongly reduced frontal theta power in the 2-back task, which parallels the P3a reduction in the ERPs. The widespread reduction of alpha may indicate that older adults needed to recruit more attentional resources for successful task performance, whereas reduced frontal theta may indicate that older adults are less able to recruit frontal resources related to top-down control with increasing task demands. This suggests a less efficient fronto-parietal network synchronicity in older individuals that leads to deficits in identification and maintenance of task relevant stimuli.
The most unexpected and intriguing result from functional brain imaging studies of cognitive aging is evidence for age-related overactivation: greater activation in older adults than in younger adults, even when performance is age-equivalent. Here we examine the hypothesis that age-related overactivation is compensatory and discuss the compensation-related utilization of neural circuits hypothesis (CRUNCH). We review evidence that favors a compensatory account, discuss questions about strategy differences, and consider the functions that may be served by overactive brain areas. Future research directed at neurocognitively informed training interventions may augment the potential for plasticity that persists into the later years of the human lifespan.
Notes that to understand the endogenous components of the event-related potential (ERP), data about the components' antecedent conditions to form hypotheses about the information-processing function of the underlying brain activity must be used. These hypotheses generate testable predictions about the consequences of the component. The application of this approach to the analysis of the P300 component is reviewed. Certain factors suggest that P300 is a manifestation of activity occurring whenever one's model of the environment must be revised. Tests of 3 predictions based on this "context updating" model are reviewed. Open peer commentary follows. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
GPOWER is a completely interactive, menu-driven program for IBM-compatible and Apple Macintosh personal computers. It performs
high-precision statistical power analyses for the most common statistical tests in behavioral research, that is,t tests,F tests, andχ
2 tests. GPOWER computes (1) power values for given sample sizes, effect sizes andα levels (post hoc power analyses); (2) sample sizes for given effect sizes,α levels, and power values (a priori power analyses); and (3)α andβ values for given sample sizes, effect sizes, andβ/α ratios (compromise power analyses). The program may be used to display graphically the relation between any two of the relevant
variables, and it offers the opportunity to compute the effect size measures from basic parameters defining the alternative
hypothesis. This article delineates reasons for the development of GPOWER and describes the program’s capabilities and handling.
Episodic memory and working memory decline with advancing age. Nevertheless, large-scale population-based studies document well-preserved memory functioning in some older individuals. The influential ‘reserve’ notion holds that individual differences in brain characteristics or in the manner people process tasks allow some individuals to cope better than others with brain pathology and hence show preserved memory performance. Here, we discuss a complementary concept, that of brain maintenance (or relative lack of brain pathology), and argue that it constitutes the primary determinant of successful memory aging. We discuss evidence for brain maintenance at different levels: cellular, neurochemical, gray- and white-matter integrity, and systems-level activation patterns. Various genetic and lifestyle factors support brain maintenance in aging and interventions may be designed to promote maintenance of brain structure and function in late life.
Working memory (WM) shows pronounced age-related decline. Functional magnetic resonance imaging (fMRI) studies have revealed age differences in task-related brain activation. Evidence based primarily on episodic memory studies suggests that brain activation patterns can be modulated by task difficulty in both younger and older adults. In most fMRI aging studies on WM, however, performance level has not been considered, so that age differences in activation patterns are confounded with age differences in performance level. Here, we address this issue by comparing younger and older low and high performers in an event-related fMRI study. Thirty younger (20-30 years) and 30 older (60-70 years) healthy adults were tested with a spatial WM task with three load levels. A region-of-interest analysis revealed marked differences in the activation patterns between high and low performers in both age groups. Critically, among the older adults, a more "youth-like" load-dependent modulation of the blood oxygen level-dependent signal was associated with higher levels of spatial WM performance. These findings underscore the need of taking performance level into account when studying changes in functional brain activation patterns from early to late adulthood.
The n-back is a putative working memory task frequently used in neuroimaging research; however, literature addressing n-back use in clinical neuropsychological evaluation is sparse. We examined convergent validity of the n-back with an established measure of working memory, digit span backward. The relationship between n-back performance and scores on measures of processing speed was also examined, as was the ability of the n-back to detect potential between-groups differences in control and Parkinson's disease (PD) groups. Results revealed no correlation
between n-back performance and digit span backward. N-back accuracy significantly correlated with a measure of processing speed (Trail Making Test Part A) at the 2-back load.
Relative to controls, PD patients performed less accurately on the n-back and showed a trend toward slower reaction times, but did not differ on any of the neuropsychological measures. Results
suggest the n-back is not a pure measure of working memory, but may be able to detect subtle differences in cognitive functioning between
PD patients and controls.
P50, N100, and P200 auditory sensory gating could reflect mechanisms involved in protecting higher-order cognitive functions, suggesting relationships between sensory gating and cognition. This hypothesis was tested in 56 healthy adults who were administered the paired-click paradigm and two adaptations of the continuous performance test (Immediate/Delayed Memory Task, IMT/DMT). Stronger P50 gating correlated with fewer commission errors and prolonged reaction times on the DMT. Stronger N100 and P200 gating correlated with better discriminability on the DMT. Finally, prolonged P200 latency related to better discriminability on the IMT. These findings suggest that P50, N100, and P200 gating could be involved in protecting cognition by affecting response bias, behavioral inhibition, working memory, or attention.
The aim of this study was to clarify which cognitive mechanisms underlie Trail Making Test (TMT) direct and derived scores. A comprehensive review of the literature on the topic was carried out to clarify which cognitive factors had been related to TMT performance. Following the review, we explored the relative contribution from working memory, inhibition/interference control, task-switching ability, and visuomotor speed to TMT performance. Forty-one healthy old subjects participated in the study and performed a battery of neuropsychological tests including the TMT, the Digit Symbol subtest [Wechsler Adult Intelligence Scale (Third Version) (WAIS-III)], a Finger Tapping Test, the Digits Forward and Backward subtests (WAIS-III), Stroop Test, and a task-switching paradigm inspired in the Wisconsin Card Sorting Test. Correlation and regression analyses were used in order to clarify the joint and unique contributions from different cognitive factors to the prediction of TMT scores. The results suggest that TMT-A requires mainly visuoperceptual abilities, TMT-B reflects primarily working memory and secondarily task-switching ability, while B-A minimizes visuoperceptual and working memory demands, providing a relatively pure indicator of executive control abilities.
Working memory capacity, the maximum number of items that we can transiently store in working memory, is a good predictor of our general cognitive abilities. Neural activity in both dorsolateral prefrontal cortex and posterior parietal cortex has been associated with memory retention during visuospatial working memory tasks. The parietal cortex is thought to store the memories. However, the role of the dorsolateral prefrontal cortex, a top-down control area, during pure information retention is debated, and the mechanisms regulating capacity are unknown. Here, we propose that a major role of the dorsolateral prefrontal cortex in working memory is to boost parietal memory capacity. Furthermore, we formulate the boosting mechanism computationally in a biophysical cortical microcircuit model and derive a simple, explicit mathematical formula relating memory capacity to prefrontal and parietal model parameters. For physiologically realistic parameter values, lateral inhibition in the parietal cortex limits mnemonic capacity to a maximum of 2-7 items. However, at high loads inhibition can be counteracted by excitatory prefrontal input, thus boosting parietal capacity. Predictions from the model were confirmed in an fMRI study. Our results show that although memories are stored in the parietal cortex, interindividual differences in memory capacity are partly determined by the strength of prefrontal top-down control. The model provides a mechanistic framework for understanding top-down control of working memory and specifies two different contributions of prefrontal and parietal cortex to working memory capacity.
High resolution evoked potentials (EPs), sampled from 115 channels and spatially sharpened with the finite element deblurring method, were recorded from 8 subjects during working memory (WM) and control tasks. The tasks required matching each stimulus with a preceding stimulus on either verbal or spatial attributes. All stimuli elicited a central P200 potential that was larger in the spatial tasks than in the verbal tasks, and larger in the WM tasks than in the control tasks. Frequent, non-matching stimuli elicited a frontal, positive peak at 305 msec that was larger in the spatial WM task relative to the other tasks. Irrespective of whether subjects attended to verbal or spatial stimulus attributes, non-matching stimuli in the WM tasks also elicited an enhanced P450 potential over the left frontal cortex, followed by a sustained potential over the superior parietal cortex. A posterior P390 potential elicited by infrequent, matching stimuli was smaller in amplitude for both spatial and verbal WM tasks compared to control tasks, as was a central prestimulus CNV. These results indicate that WM is a function of a distributed system with both task-specific and task-independent components. Lesion studies and course temporal resolution functional imaging methods, such as PET and fMRI, tend to paint a fairly static picture of the cortical regions which participate in the performance of WM tasks. In contrast, the fine-grain time resolution provided by imaging brain function with EP methods provides a dynamic picture of subsecond changes in the spatial distribution of WM effects over the course of individual trials, as well as evidence for differences in the activity elicited by matching and non-matching stimuli within sequences of trials. This information about the temporal dynamics of WM provides a critical complement to the fine-grain spatial resolution provided by other imaging modalities.
A total of 73 healthy subjects aged 20-86 years performed an auditory 'oddball' task. The age-dependence of N1 and P2 elicited by non-target stimuli, of N2 and P3 elicited by target stimuli and of N2a and N2b components (target minus non-target difference waves) was investigated across 20 electrodes to detect any aging-related changes in the psychophysiological processing of such stimuli during the task. Aging-related differences in within-task changes in non-target ERPs were also investigated. In non-target ERPs, it was found that P2 amplitude at Fz increased linearly with advancing age and the analysis of within-task changes indicated that P2 amplitude decreased during the task in young subjects at Pz, but remained unchanged in middle-aged and elderly subjects. These results suggest the existence of aging-related inhibitory deficits that may hinder the disengagement of attentional resources from irrelevant stimuli during the task. In the target ERPs, the latencies of N2 and P3 increased linearly at Fz, Cz and Pz. The increases in N2 were mainly due to linear increases in N2b latency at Fz, Cz and Pz, indicating that the aging-related slowing begins at controlled memory comparison of non-target/target stimuli. P3 amplitude presented a more uniform scalp distribution in middle-aged and in elderly subjects and pnly decreased significantly with advancing age in men, which may explain the divergent results in the literature on aging-related changes of P3 amplitude.
Working memory (WM), the ability to briefly retain and manipulate information in mind, is central to intelligent behavior. Here we take advantage of the high temporal resolution of electrophysiological measures to obtain a millisecond timescale view of the activity induced in distributed cortical networks by tasks that impose significant WM demands. We examined how these networks are affected by the type and amount of information to be remembered, and by the amount of task practice. Evoked potentials (EPs) were obtained from eight subjects performing spatial and verbal versions of a visual n-back WM task (n = 1, 2, 3) on each of three testing days. In well-trained subjects, WM tasks elicited transient responses reflecting different subcomponents of task processing, including transient (lasting 0.02-0.3 s) task-sensitive and load-sensitive EPs, as well as sustained responses (lasting 1-1.5 s), including the prestimulus Contingent Negative Variation (CNV), and post-stimulus frontal and parietal Slow Waves. The transient responses, with the exception of the P300, differed between the verbal and spatial task versions, and between trials with different response requirements. The P300 and the Slow Waves were not affected by task version but were affected by increased WM load. These results suggest that WM emerges from the formation of a dynamic cortical network linking task-specific processes with non-specific, capacity-limited, higher-order attentional processes. Practice effects on the EPs suggested that practice led to the development of a more effective cognitive strategy for dealing with lower-order aspects of task processing, but did not diminish demands made on higher order processes. Thus a simple WM task is shown to be composed of numerous elementary subsecond neural processes whose characteristics vary with type and amount of information being remembered, and amount of practice.
Age-related decline in working memory figures prominently in theories of cognitive aging. However, the effects of aging on the neural substrate of working memory are largely unknown. Positron emission tomography (PET) was used to investigate verbal and spatial short-term storage (3 sec) in older and younger adults. Previous investigations with younger subjects performing these same tasks have revealed asymmetries in the lateral organization of verbal and spatial working memory. Using volume of interest (VOI) analyses that specifically compared activation at sites identified with working memory to their homologous twin in the opposite hemisphere, we show pronounced age differences in this organization, particularly in the frontal lobes: In younger adults, activation is predominantly left lateralized for verbal working memory, and right lateralized for spatial working memory, whereas older adults show a global pattern of anterior bilateral activation for both types of memory. Analyses of frontal subregions indicate that several underlying patterns contribute to global bilaterality in older adults: most notably, bilateral activation in areas associated with rehearsal, and paradoxical laterality in dorsolateral prefrontal sites (DLPFC; greater left activation for spatial and greater right activation for verbal). We consider several mechanisms that could account for these age differences including the possibility that bilateral activation reflects recruitment to compensate for neural decline.
The capacity to deliberately control attention in order to hold and manipulate information in working memory is critical to higher cognitive functions. This suggests that between-subject differences in general cognitive ability might be related to observable differences in the activity of brain systems that support working memory and attention control. To test this notion, electroencephalograms were recorded from 80 healthy young adults during spatial working memory tasks. Measures of task-related neurophysiological and behavioral variables were derived from these data and compared to scores on a test battery commonly used to assess general cognitive ability (the WAIS-R). Subjects who scored high on the psychometric test also tended to respond faster in the experimental tasks without any loss of accuracy. The amplitude of the late positive component of the event-related potential was larger in high-ability subjects, and the frontal midline theta component of the EEG signal was also selectively enhanced in this group under conditions of sustained performance and high working memory load. These results suggest that subjects who scored high on the WAIS-R were better able to focus and sustain attention to task performance. Changes in the EEG alpha rhythm in response to manipulations of task practice and load were also examined and compared between frontal and parietal regions. The results indicated that high-ability subjects developed strategies that made relatively greater use of parietal regions, whereas low-ability subjects relied more exclusively on frontal regions. Other analyses indicated that hemispheric asymmetries in alpha band measures distinguish between individuals with relatively high verbal aptitude and those with relatively high nonverbal aptitude. In particular, subjects with a verbal cognitive style tended to make greater use of the left parietal region during task performance, and subjects with a nonverbal style tended to make greater use of the right parietal region. These results help clarify relationships between task-related brain activity and individual differences in cognitive ability and style.
To examine how neurophysiological signals of working memory (WM) change with normal aging, we recorded EEGs from healthy groups (n=10 each) of young (mean age=21 years), middle-aged (mean=47 years), and older (mean=69 years) adults. EEGs were recorded while subjects performed easy and difficult versions of a spatial WM task. Groups were matched for IQ (mean=123; WAIS-R) and practiced in task performance. Responses slowed with age, particularly in the more difficult task. Advanced age was associated with decreased amplitude and increased latency of the parietal P300 component of the event-related potential and an increase in the amplitude of a frontal P200 component. Spectral features of the EEG also differed between groups. Younger subjects displayed an increase in the frontal midline θ rhythm with increased task difficulty, a result not observed in older subjects. Age-related changes were also observed in the task-related alpha signal, the amplitude of which decreases as more neurons become involved in task-related processing. Young adults showed a decrease in alpha power with increased task difficulty over parietal regions but not over frontal regions. Middle-aged and older adults showed decreased alpha power with increased task difficulty over both frontal and parietal regions. This suggests that normal aging may be associated with changes in the fronto-parietal networks involved with spatial WM processes. Younger subjects appear to use a strategy that relies on parietal areas involved with spatial processing, whereas older subjects appear to use a strategy that relies more on frontal areas.
The authors investigated the distinctiveness and interrelationships among visuospatial and verbal memory processes in short-term, working, and long-term memories in 345 adults. Beginning in the 20s, a continuous, regular decline occurs for processing-intensive tasks (e.g., speed of processing, working memory, and long-term memory), whereas verbal knowledge increases across the life span. There is little differentiation in the cognitive architecture of memory across the life span. Visuospatial and verbal working memory are distinct but highly interrelated systems with domain-specific short-term memory subsystems. In contrast to recent neuroimaging data, there is little evidence for dedifferentiation of function at the behavioral level in old compared with young adults. The authors conclude that efforts to connect behavioral and brain data yield a more complete understanding of the aging mind.
Using the n-back task, we recently identified, in young subjects, a positive-negative event related potential component (PN(wm)) in a time-range window between 140 and 280 ms after stimulus onset representing an electrophysiological correlate of working memory load. To evaluate age-related electrophysiological changes in working memory processing, we applied the same neuropsychological paradigm and compared densities of the PN(wm) component in 17 young (mean age: 26) and 17 healthy elderly individuals (mean age: 75). Both age groups displayed a PN(wm) component during the two working memory tasks. For the 1-back task, densities were similar in both young and elderly individuals. In contrast, PN(wm) densities increased with higher memory load (2-back>1-back) in the younger but not in the older group. This difference was mainly observed over parietal electrodes suggesting an impaired activation of neural generators within this brain region. The present results are consistent with the hypothesis of decreased brain reserve in the elderly and provide evidence for age-related deficits in the recruitment of posterior cortical neurons with increasing working memory load.
Working memory has been conceptualized as consisting of a number of components, such as an articulatory loop for rehearsing verbal material, a visuo-spatial sketch pad for maintaining visual images and a central executive that controls which information is made available for conscious processing. We recorded event-related brain potentials (ERPs) from normal human subjects while they maintained either visuo-spatial or phonological material in short-term memory for a 5-s interval. The results indicated that specialized brain systems for short-term storage of phonological and visuo-spatial information could be identified on the basis of marked differences between the topographies and morphologies of the ERP components elicited during these two types of short-term memory. The differences emerged during early encoding stages and continued through later retention stages.
In this study, we assess the impact of normal aging on top-down modulation, a cognitive control mechanism that supports both attention and memory by the suppression and enhancement of sensory processing in accordance with task goals. Using fMRI (functional magnetic resonance imaging), we show that healthy older adults demonstrated a prominent deficit in the suppression of cortical activity associated with task-irrelevant representations, whereas enhancement of task-relevant activity was preserved. Moreover, this suppression-specific attention deficit correlated with impaired working memory performance.
A consistent finding from functional neuroimaging studies of cognitive aging is an age-related reduction in occipital activity coupled with increased frontal activity. This posterior-anterior shift in aging (PASA) has been typically attributed to functional compensation. The present functional magnetic resonance imaging sought to 1) confirm that PASA reflects the effects of aging rather than differences in task difficulty; 2) test the compensation hypothesis; and 3) investigate whether PASA generalizes to deactivations. Young and older participants were scanned during episodic retrieval and visual perceptual tasks, and age-related changes in brain activity common to both tasks were identified. The study yielded 3 main findings. First, inconsistent with a difficulty account, the PASA pattern was found across task and confidence levels when matching performance among groups. Second, supporting the compensatory hypothesis, age-related increases in frontal activity were positively correlated with performance and negatively correlated with the age-related occipital decreases. Age-related increases and correlations with parietal activity were also found. Finally, supporting the generalizability of the PASA pattern to deactivations, aging reduced deactivations in posterior midline cortex but increased deactivations in medial frontal cortex. Taken together, these findings demonstrate the validity, function, and generalizability of PASA, as well as its importance for the cognitive neuroscience of aging.
Working memory, the ability to store and simultaneously manipulate information, is affected in several neuropsychiatric disorders which lead to severe cognitive and functional deficits. An electrophysiological marker for this process could help identify early cerebral function abnormalities. In subjects performing working memory-specific n-back tasks, event-related potential analysis revealed a positive-negative waveform (PNwm) component modulated in amplitude by working memory load. It occurs in the expected time range for this process, 140-280 ms after stimulus onset, superimposed on the classical P200 and N200 components. Independent Component Analysis extracted two functional components with latencies and topographical scalp distributions similar to the PNwm. Our results imply that the PNwm represents a new electrophysiological index for working memory load in humans.
The term working memory refers to a brain system that provides temporary storage and manipulation of the information necessary for such complex cognitive tasks as language comprehension, learning, and reasoning. This definition has evolved from the concept of a unitary short-term memory system. Working memory has been found to require the simultaneous storage and processing of information. It can be divided into the following three subcomponents: (i) the central executive, which is assumed to be an attentional-controlling system, is important in skills such as chess playing and is particularly susceptible to the effects of Alzheimer's disease; and two slave systems, namely (ii) the visuospatial sketch pad, which manipulates visual images and (iii) the phonological loop, which stores and rehearses speech-based information and is necessary for the acquisition of both native and second-language vocabulary.
Performance on measures of working memory (WM) capacity predicts performance on a wide range of real-world cognitive tasks. I review the idea that WM capacity (a) is separable from short-term memory, (b) is an important component of general fluid intelligence, and (c) represents a domain-free limitation in ability to control attention. Studies show that individual differences in WM capacity are reflected in performance on antisaccade, Stroop, and dichotic-listening tasks. WM capacity, or executive attention, is most important under conditions in which interference leads to retrieval of response tendencies that conflict with the current task.
Working memory is a construct of primary relevance to many areas of psychology. Two types of tasks have been used to measure working memory, primarily in different research areas: Complex span tasks are commonly used in behavioral studies in the cognitive and individual-differences literature, whereas n-back tasks have been used more frequently in cognitive neuroscience studies investigating the neural underpinnings of working memory. Despite both categories of tasks being labeled as "working memory" measures, previous empirical studies have provided mixed evidence regarding the shared amount of overlapping processes between complex span and n-back tasks. The present meta-analysis showed that the complex span and n-back tasks are weakly correlated, although significant heterogeneity across studies was observed. A follow-up analysis of unpublished data indicated that the sample composition affects the relationship between the complex span and n-back tasks, following the law of diminishing returns. Finally, a separate meta-analysis indicated that the simple span and n-back tasks are correlated to the same extent as are the complex span and n-back tasks. The present findings indicate that the complex span and n-back tasks cannot be used interchangeably as working memory measures in research applications.
This study investigated age-related changes in the early processing of novel visual stimuli using ERPs. Well-matched old (n = 30), middle-aged (n = 30), and young (n = 32) subjects were presented standard, target/rare, and perceptually novel visual stimuli under Attend and Ignore conditions. Our results suggest that the anterior P2 component indexes the motivational salience of a stimulus as determined by either task relevance or novelty. Its enhancement by focused attention does not decrease with age. Its responsiveness to novel stimuli is particularly striking in older adults. The age-related increase in the anterior P2 to novel visual stimuli does not appear to be due to impaired inhibitory control associated with aging. Rather, the enhanced anterior P2 to novel stimuli in older adults may be linked to age-related changes in the process of matching unusual visual stimuli to stored representations, which is indexed by the temporally overlapping anterior N2 component whose amplitude substantially decreases with age.
Previous functional imaging studies have pointed to the compensatory recruitment of cortical circuits in old age in order to counterbalance the loss of neural efficiency and preserve cognitive performance. Recent electroencephalographic (EEG) analyses reported age-related deficits in the amplitude of an early positive-negative working memory (PN(wm)) component as well as changes in working memory (WM)-load related brain oscillations during the successful performance of the n-back task. To explore the age-related differences of EEG activation in the face of increasing WM demands, we assessed the PN(wm) component area, parietal alpha event-related synchronization (ERS) as well as frontal theta ERS in 32 young and 32 elderly healthy individuals who successfully performed a highly WM demanding 3-back task. PN(wm) area increased with higher memory loads (3- and 2-back > 0-back tasks) in younger subjects. Older subjects reached the maximal values for this EEG parameter during the less WM demanding 0-back task. They showed a rapid development of an alpha ERS that reached its maximal amplitude at around 800 ms after stimulus onset. In younger subjects, the late alpha ERS occurred between 1,200 and 2,000 ms and its amplitude was significantly higher compared with elders. Frontal theta ERS culmination peak decreased in a task-independent manner in older compared with younger cases. Only in younger individuals, there was a significant decrease in the phasic frontal theta ERS amplitude in the 2- and 3-back tasks compared with the detection and 0-back tasks. These observations suggest that older adults display a rapid mobilization of their neural generators within the parietal cortex to manage very low demanding WM tasks. Moreover, they are less able to activate frontal theta generators during attentional tasks compared with younger persons.
Active and passive measures of short-term memory over a large segment of the adult life span were compared. Two hundred twenty-eight volunteers, aged 30 to 99 years, performed the digit span forward and backward task, the Peterson-Peterson task, and a new working memory task in which active manipulation of information is emphasized. Age differences were slight for passive tasks. For the working memory task, significant declines were found between the ages of 60 to 69 and 70+ years. It is suggested that the age differences may be due to a decrease in the flexibility with which processing changes are made.
Research in aging has emphasized average age-related losses and neglected the substantial heterogeneity of older persons.
The effects of the aging process itself have been exaggerated, and the modifying effects of diet, exercise, personal habits,
and psychosocial factors underestimated. Within the category of normal aging, a distinction can be made between usual aging,
in which extrinsic factors heighten the effects of aging alone, and successful aging, in which extrinsic factors play a neutral
or positive role. Research on the risks associated with usual aging and strategies to modify them should help elucidate how
a transition from usual to successful aging can be facilitated.
The general purpose of this study was to describe differences in intellectual functioning associated with aging in adulthood. Estimates of broad factors identified as fluid intelligence, crystallized intelligence, general visualization, speediness, carefulness and fluency were obtained by combining scores on several tests found to define these factors in previous research. A sample of 297 subjects was divided into five age groupings: 14–17 year-olds, 18–20 year-olds, 21–28 year-olds, 29–39 year-olds and 40–61 year-olds. Analyses of variance and covariance were carried out on these factors and age groupings, using sex and education, as well as the factors themselves, as covariates. These analyses revealed that:(a) The mean level of fluid intelligence was systematically higher for younger adults (relative to older adults),(b) The mean level of crystallized intelligence was systematically higher for older adults (relative to younger adults),(c) The mean for the general visualization function was highest for the grouping of 21–28 year-olds and the means systematically dropped off on either side of the high value,(d) No systematic age trends were discernible for the general speediness, carefulness and fluency factors.These results provided support for the theory of fluid and crystallized intelligence.
In a study (N = 61) comparing older (age range = 60-80 years, M = 67) and younger (age range = 20-33 years, M = 25) people, age deficits were observed in working memory, perceptual speed, and central executive functioning but not in phonological loop functioning. Controlling for age differences in central executive performance removed over 50% of the age-related variance in working memory span. However, controlling for perceptual speed removed all of the age-related variance in working memory span. In addition, age differences in central executive functioning were largely eliminated after controlling for age deficits in perceptual speed. These findings suggest that age differences in central executive functioning are primarily attributable to a general slowdown in the rate at which information is activated within the working memory system and that no specific deficits in the central executive occur as a consequence of aging.
In 3 separate experiments, the same samples of young and older adults were tested on verbal and visuospatial processing speed tasks, verbal and visuospatial working memory tasks, and verbal and visuospatial paired-associates learning tasks. In Experiment 1, older adults were generally slower than young adults on all speeded tasks, but age-related slowing was much more pronounced on visuospatial tasks than on verbal tasks. In Experiment 2, older adults showed smaller memory spans than young adults in general, but memory for locations showed a greater age difference than memory for letters. In Experiment 3, older adults had greater difficulty learning novel information than young adults overall, but older adults showed greater deficits learning visuospatial than verbal information. Taken together, the differential deficits observed on both speeded and unspeeded tasks strongly suggest that visuospatial cognition is generally more affected by aging than verbal cognition.
In 1974, Baddeley and Hitch proposed a three-component model of working memory. Over the years, this has been successful in giving an integrated account not only of data from normal adults, but also neuropsychological, developmental and neuroimaging data. There are, however, a number of phenomena that are not readily captured by the original model. These are outlined here and a fourth component to the model, the episodic buffer, is proposed. It comprises a limited capacity system that provides temporary storage of information held in a multimodal code, which is capable of binding information from the subsidiary systems, and from long-term memory, into a unitary episodic representation. Conscious awareness is assumed to be the principal mode of retrieval from the buffer. The revised model differs from the old principally in focussing attention on the processes of integrating information, rather than on the isolation of the subsystems. In doing so, it provides a better basis for tackling the more complex aspects of executive control in working memory.
The n-back task was hypothesized to be a dual task, permitting the imposition of parametrically increasing attentional and working memory demands, while keeping constant the demands of an embedded matching subtask. Visual targets were presented for 200 ms every 2.2 s at pseudorandomly varying positions on a computer screen. Participants were required to remember the most recent 0, 1, 2, or 3 positions and responded with a choice button push to whether the current target position matched the position presented n items previously. P300 peak latency was constant across n-back tasks, reflecting constant perceptual and cognitive demands of the matching subtask. P300 peak amplitude decreased with increasing memory load, reflecting reallocation of attention and processing capacity away from the matching subtask to working memory activity. These data support a dual-task nature of the n-back, which should be considered when employing this paradigm.
Proclaims that signal detection theory seems to provide a framework for a realistic description of the behavior of the human observer in a variety of perceptual tasks. The particular feature of the theory that was of greatest interest to the authors was the promise of solving an old problem in the field of psychophysics. This is the problem of controlling or specifying the criterion that the observer uses in making a perceptual judgment. This paper begins with a brief review of the theory of statistical decision and then presents a description of the elements of the theory of signal detection appropriate to human observers. Following this, the results of some experimental tests of the applicability of the theory to the detection of visual signals are described. The paper also contains a description of the theory, an account of a previously reported experiment, and the results of four other experiments. The authors believe that the article brings together all of the data collected to date in vision experiments that bear directly on the value of the theory.
The concept of working memory proposes that a dedicated system maintains and stores information in the short term, and that this system underlies human thought processes. Current views of working memory involve a central executive and two storage systems: the phonological loop and the visuospatial sketchpad. Although this basic model was first proposed 30 years ago, it has continued to develop and to stimulate research and debate. The model and the most recent results are reviewed in this article.
Early investigations of working memory capacity (WMC) and reasoning ability suggested that WMC might be the basis of Spearman's g. However, recent work has uncovered details about the basic processes involved in working memory tasks, which has resulted in a more principled approach to task development. As a result, claims now being made about the relation between WMC and g are more cautious. A review of the recent research reveals that WMC and g are indeed highly related, but not identical. Furthermore, WM span tasks involve an executive-control mechanism that is recruited to combat interference and this ability is mediated by portions of the prefrontal cortex. More combined experimental-differential research is needed to understand better the basis of the WMC-g relation.
Cognitive abilities such as working memory (WM) capacity decrease with age. To determine the neurophysiological correlates of age-related reduction in working memory capacity, we studied 10 young subjects (<35 years of age; mean age=29) and twelve older subjects (>55 years of age; mean age=59) with whole brain blood oxygenation-level dependent (BOLD) fMRI on a 1.5 T GE MR scanner using a SPIRAL FLASH pulse sequence (TE=24 ms, TR=56 ms, FA=60 degrees , voxel dimensions=3.75 mm(3)). Subjects performed a modified version of the "n" back working memory task at different levels of increasing working memory load (1-Back, 2-Back and 3-Back). Older subjects performed as well as the younger subjects at 1-Back (p=0.4), but performed worse than the younger subjects at 2-Back (p<0.01) and 3-Back (p=0.06). Older subjects had significantly longer reaction time (RT) than younger subjects (p<0.04) at all levels of task difficulty. Image analysis using SPM 99 revealed a similar distribution of cortical activity between younger and older subjects at all task levels. However, an analysis of variance revealed a significant group x task interaction in the prefrontal cortex bilaterally; within working memory capacity, as in 1-Back when the older subjects performed as well as the younger subjects, they showed greater prefrontal cortical (BA 9) activity bilaterally. At higher working memory loads, however, when they performed worse then the younger subjects, the older subjects showed relatively reduced activity in these prefrontal regions. These data suggest that, within capacity, compensatory mechanisms such as additional prefrontal cortical activity are called upon to maintain proficiency in task performance. As cognitive demand increases, however, they are pushed past a threshold beyond which physiological compensation cannot be made and, a decline in performance occurs.
Working memory and short-term memory are closely related in their cognitive architecture, capacity limitations, and functional neuroanatomy, which only partly overlap with those of long-term memory. The author reviews the functional neuroimaging literature on the commonalities and differences between working memory and short-term memory and the interplay of areas with modality-specific and supramodal representations in the brain networks supporting these fundamental cognitive processes. Sensory stores in the visual, auditory, and somatosensory cortex play a role in short-term memory, but supramodal parietal and frontal areas are often recruited as well. Classical working memory operations such as manipulation, protection against interference, or updating almost certainly require at least some degree of prefrontal support, but many pure maintenance tasks involve these areas as well. Although it seems that activity shifts from more posterior regions during encoding to more anterior regions during delay, some studies reported sustained delay activity in sensory areas as well. This spatiotemporal complexity of the short-term memory/working memory networks is mirrored in the activation patterns that may explain capacity constraints, which, although most prominent in the parietal cortex, seem to be pervasive across sensory and premotor areas. Finally, the author highlights open questions for cognitive neuroscience research of working memory, such as that of the mechanisms for integrating different types of content (binding) or those providing the link to long-term memory.
The empirical and theoretical development of the P300 event-related brain potential (ERP) is reviewed by considering factors that contribute to its amplitude, latency, and general characteristics. The neuropsychological origins of the P3a and P3b subcomponents are detailed, and how target/standard discrimination difficulty modulates scalp topography is discussed. The neural loci of P3a and P3b generation are outlined, and a cognitive model is proffered: P3a originates from stimulus-driven frontal attention mechanisms during task processing, whereas P3b originates from temporal-parietal activity associated with attention and appears related to subsequent memory processing. Neurotransmitter actions associating P3a to frontal/dopaminergic and P3b to parietal/norepinephrine pathways are highlighted. Neuroinhibition is suggested as an overarching theoretical mechanism for P300, which is elicited when stimulus detection engages memory operations.
Recent studies described several changes of endogenous event-related potentials (ERP) and brain rhythm synchronization during memory activation in patients with Alzheimer's disease (AD). To examine whether memory-related EEG parameters may predict cognitive decline in mild cognitive impairment (MCI), we assessed P200 and N200 latencies as well as beta event-related synchronization (ERS) in 16 elderly controls (EC), 29 MCI cases and 10 patients with AD during the successful performance of a pure attentional detection task as compared with a highly working memory demanding two-back task. At 1 year follow-up, 16 MCI patients showed progressive cognitive decline (PMCI) and 13 remained stable (SMCI). Both P200 and N200 latencies in the two-back task were longer in PMCI and AD cases compared with EC and SMCI cases. During the interval 1000 ms to 1700 ms after stimulus, beta ERS at parietal electrodes was of lower amplitude in PMCI and AD compared with EC and SMCI cases. Univariate models showed that P200, N200 and log% beta values were significantly related to the SMCI/PMCI distinction with areas under the receiver operating characteristic curve of 0.93, 0.78 and 0.72, respectively. The combination of all three EEG hallmarks was the stronger predictor of MCI deterioration with 90% of correctly classified MCI cases. Our data reveal that PMCI and clinically overt AD share the same pattern of working memory-related EEG activation characterized by increased P200-N200 latencies and decreased beta ERS. They also show that P200 latency during the two-back task may be a simple and promising EEG marker of rapid cognitive decline in MCI.