High resolution evoked potential imaging of the cortical dynamics of human working memory

Common and distinct neural substrates of rule- and similarity-based category learning

Categorization is a fundamental ability in human cognition that enables generalization and promotes decision-making. A categorization problem can be solved by employing a rule-based or a similarity-based strategy. The current study aims to elucidate the brain mechanism for category learning by investigating whether the use of the two strategies is supported by common or distinct neural substrates. We conducted three experiments using stimuli with a rule-plus-similarity category structure and applying an EEG-fNIRS fusion methodology. In Experiment 1, participants were explicitly instructed to use either a rule-based (single feature) or a similarity-based strategy, while in Experiment 3, they were instructed to use a rule-based (multi-feature) or a similarity-based strategy. In contrast, in Experiment 2, participants were required to self-discover categorization strategies. After learning, categorization was tested. The results of the three experiments were largely consistent, revealing distinct decision-making processes associated with each strategy. The results revealed that hypothesis testing and semantic processing, as reflected by the larger P300 and N400 components and increased activation in Wernicke's area, were critical for rule-based category learning, suggesting the role of an explicit system. In contrast, complex visual processing and the integration of multiple features, as indicated by a larger P1 component and the heightened activation in the frontopolar cortex, were critical for similarity-based category learning, suggesting the role of an implicit system. These distinct cognitive processes challenge single-system accounts suggesting a unified neural mechanism for both forms of category learning. Instead, our findings are consistent with the COVIS theory, which implies an explicit system for rule-based category learning and an implicit system for similarity-based category learning.

Do emotionally negative events impair working memory as a result of intrusive thoughts?

Individuals exposed to highly stressful negative events show alterations in working memory (WM) function. The correlational nature of these studies makes it impossible to determine whether exposure to negative events itself decreases WM. Such events elicit intrusive thoughts which may cause interference in WM. The main objective of this study was to verify the causal impact of a recent negative event on WM, and to examine the role of intrusive thoughts. One hundred and twenty participants completed a WM task (n-Back). Then, 90 of these participants watched an emotionally negative video and 30 watched a neutral video. The emotional impact of the video was assessed, and the frequency of intrusive thoughts were measured. WM was measured a second time (n-Back) while recording EEG (P300). Contrary to our hypothesis, the negative video did not impair behavioural WM performance compared to the neutral video. However, it disrupted WM neurocognitive processes (lower P300 amplitude) under low WM load. In the high load condition, greater emotional reaction was linked to poorer accuracy and more intrusive thoughts, which in turn slowed response times. Our results suggest that the impact of negative emotions on WM depends on both individual sensitivity and cognitive load.

The mutual influences between working memory and empathy for pain: the role of social distance

Understanding the mechanisms behind the interaction of empathy for pain (EfP) and working memory (WM), particularly how they are influenced by social factors like perceived social distance (SD), is vital for comprehending how humans dynamically adapt to the complexities of social life. However, there is very little known about these mechanisms. Accordingly, we recruited 116 healthy participants to investigate the bidirectional influence and electrophysiological responses between WM and EfP, including the role of SD. Our research results revealed that the interaction between WM load and SD significantly influenced the processing of EfP. Specifically, high WM load and distant SD facilitated early processing of EfP. Conversely, low WM load and close SD promoted late processing of EfP. Furthermore, the interaction between EfP and SD significantly influenced the performance of ongoing WM tasks. Specifically, the kin's pain, compared to kin's nonpain, improved the participant's performance on low-load WM tasks; however, it diminished the participant's performance on tasks with high WM load. Overall, these results provide evidence at both behavioral and neural levels for the mutual influence of WM and EfP during the same temporal process, and SD emerged as a crucial moderating factor during these mutual influences.

Age-related changes in brain oscillatory patterns during an n-back task in children and adolescents

The development of brain oscillatory responses and their possible role in the working memory (WM) performance of children, adolescents and young adults was investigated. A set of 0- and 1-back tasks with letter stimuli were administered to a final sample of 131 subjects (between 6 and 20 years of age). A decrease in response times (RTs) and an increase of the sensitivity index d-prime (d') were seen with increased age. RTs increased and d' decreased with load, indicating higher difficulty for higher loads. Event-related synchronization (ERS) and event-related desynchronization (ERD) were obtained by the convolution of Morlet wavelets on the recorded EEG. Statistical analyses were performed of the absolute and relative power of brain oscillations defined by topography, frequency and latency. Posterior alpha and beta ERD, and frontocentral theta ERS, were induced by the stimuli presented during the n-back task. While relative theta ERS increased with age, absolute theta ERS, absolute and relative alpha and, absolute beta ERD, decreased with age. Age-related improvement in behavioral performance was mediated by relative theta. Alpha and beta ERD were more pronounced for the most difficult task (1-back) and for the target condition. Globally, there was high consistency of the effects of target type and task load across development. Theta ERS maturation is a crucial step for improving WM performance during development, while alpha and beta ERD maturation seem to be less critical for behavioral performance improvement with age, possibly due to a sufficient level of alpha-beta ERD for good performance in young children.

The common factor of executive functions measures nothing but speed of information uptake

There is an ongoing debate about the unity and diversity of executive functions and their relationship with other cognitive abilities such as processing speed, working memory capacity, and intelligence. Specifically, the initially proposed unity and diversity of executive functions is challenged by discussions about (1) the factorial structure of executive functions and (2) unfavorable psychometric properties of measures of executive functions. The present study addressed two methodological limitations of previous work that may explain conflicting results: The inconsistent use of (a) accuracy-based vs. reaction time-based indicators and (b) average performance vs. difference scores. In a sample of 148 participants who completed a battery of executive function tasks, we tried to replicate the three-factor model of the three commonly distinguished executive functions shifting, updating, and inhibition by adopting data-analytical choices of previous work. After addressing the identified methodological limitations using drift-diffusion modeling, we only found one common factor of executive functions that was fully accounted for by individual differences in the speed of information uptake. No variance specific to executive functions remained. Our results suggest that individual differences common to all executive function tasks measure nothing more than individual differences in the speed of information uptake. We therefore suggest refraining from using typical executive function tasks to study substantial research questions, as these tasks are not valid for measuring individual differences in executive functions.

The influence of perceptual and semantic chunking on the neural mechanism of remote association

Studies on remote association tests (RATs) have mainly focused on cognitive processes involved in searching for remote associations. However, factors affecting these search processes and remote associations remain unclear. In order to address this issue, this study compared non-chunking condition (e.g., "//") with perceptual chunking (two red color characters in the three-character item "//") and semantic chunking (high-frequency word-pair in the item; e.g., "//", "," literally "philosophy") conditions in the Chinese Remote Association Test (CRAT). The behavioral results on the CRAT found that the semantic ones resulted in significantly lower successful solving rates and longer response times than the other two conditions. The event-related potential (ERP) results showed that in contrast to the perceptual-chunking and the non-chunking condition, the semantic-chunking elicited enhanced P200, which might be related to the intuitive awareness of the mental fixation. However, relative to the non-chunking condition, the two chunking conditions evoked increased N400 and late positive component (LPC), indexing the late reflection and implementation of cognitive control. Our results suggest that it is the early awareness of the semantic chunk, rather than the general cognitive control process involved in representing and solving the semantically and perceptually chunk-induced interferences, that critically determines the final solving of RATs.

Stroop in motion: Neurodynamic modulation underlying interference control while sitting, standing, and walking

There is conflicting evidence about how interference control in healthy adults is affected by walking as compared to standing or sitting. Although the Stroop paradigm is one of the best-studied paradigms to investigate interference control, the neurodynamics associated with the Stroop task during walking have never been studied. We investigated three Stroop tasks using variants with increasing interference levels - word-reading, ink-naming, and the switching of the two tasks, combined in a systematic dual-tasking fashion with three motor conditions - sitting, standing, and treadmill walking. Neurodynamics underlying interference control were recorded using the electroencephalogram. Worsened performance was observed for the incongruent compared to congruent trials and for the switching Stroop compared to the other two variants. The early frontocentral event-related potentials (ERPs) associated with executive functions (P2, N2) differentially signaled posture-related workloads, while the later stages of information processing indexed faster interference suppression and response selection in walking compared to static conditions. The early P2 and N2 components as well as frontocentral Theta and parietal Alpha power were sensitive to increasing workloads on the motor and cognitive systems. The distinction between the type of load (motor and cognitive) became evident only in the later posterior ERP components in which the amplitude non-uniformly reflected the relative attentional demand of a task. Our data suggest that walking might facilitate selective attention and interference control in healthy adults. Existing interpretations of ERP components recorded in stationary settings should be considered with care as they might not be directly transferable to mobile settings.

Involvement of executive control in neural capacity related to working memory in aging: an ERP P300 study

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 age-related 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.

Repetitive Anodal TDCS to the Frontal Cortex Increases the P300 during Working Memory Processing

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.

Event-Related Potentials as Markers of Efficacy for Combined Working Memory Training and Transcranial Direct Current Stimulation Regimens: A Proof-of-Concept Study

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.

Total Sleep Deprivation Triggers Greater Activation in the Parietal Brain in the Visual Working Memory Updating Processes: An Event-Related Potentials Study

Working memory functions are known to be altered after total sleep deprivation (TSD). However, few studies have explored the deficits of working memory updating (WMU) after TSD, or the underlying electrophysiological mechanisms of these alterations. In the current exploratory study, we enrolled 14 young male volunteers who performed two kinds of WMU tasks—spatial and object two-back tasks—with simultaneous electroencephalography recordings under two sleep conditions: a normal sleep baseline condition and after 36 h of TSD. Repeated-measures analysis of variance showed that compared with those at baseline, the rates of correct responses in the WMU tasks decreased significantly after TSD. Analysis of event-related potentials revealed that the average amplitude of P3 components decreased significantly in the frontal and central brain regions and increased significantly in the parietal brain regions. Our findings suggest that TSD damages WMU behavior, impairs cognitive functions in the frontal and central brain regions, and triggers greater activation in the parietal brain regions. This is the first study to report the existence of event-related compensatory neural activity. This event-related compensatory effect may provide a new perspective for understanding the mechanisms underlying the influences triggered by sleep loss.

EEG/ERP evidence of possible hyperexcitability in older adults with elevated beta-amyloid

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.

Kidney transplantation and action-intentional improvements: Evidence from an ERP study

Reaction slowing observed in dialyzed patients results from deficits in initiating and sustaining motor response mobilization. The present study aimed at investigating whether these deficits are reversible following successful kidney transplantation. To achieve this goal, behavioral and electrophysiological (EEG) data were assessed from healthy control participants as well as kidney transplant and dialyzed patients performing a series of reaction time tasks. The results demonstrated that in patients who received kidney transplant a normalization of response latencies and brain preparatory activity was observed. At the same time, when compared to healthy individuals, increased attention engagement was observed in both clinical groups of patients. No behavioral and electrophysiological indices of impaired monitoring were observed in any of the clinical groups.

Neural and Retinal Characteristics in Relation to Working Memory in Older Adults with Mild Cognitive Impairment

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 densities 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.

Event-related potentials of episodic encoding after traumatic brain injury in older adults

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.

Age-related changes in selection, recognition, updating and maintenance information in WM. An ERP study in children and adolescents

Possible age-related changes in different working memory (WM) subcomponents were assessed by analyzing the event-related-potentials associated with the n-back task. Two versions of the task (0- and 1-back) were administered to 168 subjects between 6 and 20 years of age. In both n-back tasks, lists of symbol-letter pairs were presented. Participants had to select the letter and decide whether it matched the target in memory. Selection-matching of the relevant item, as indexed by an N2pc component, was evident in all age groups, indicating early maturation of this ability. The decreasing amplitude of the P300 with age, coupled with the longer duration of the load effect in young children, suggests that WM updating requires greater processing resources at younger ages. The slow wave, present during the maintenance period, showed an inversion of polarity with age in anterior sites that could reflect age-related changes in the active maintenance of information in WM.

Organization framework and preliminary findings from the Athens First-Episode Psychosis Research Study

AIMS

Athens First-Episode Psychosis (FEP) Research study, aims to explore the potential associations between multiple genetic, environmental and neurometabolic risk factors of psychotic disorders, through the clinical management of FEP patients with minimal exposure (<2 weeks) to antipsychotic treatment at entry. The goal of this paper is to introduce the background, rationale and design of the study and present its preliminary findings.

METHODS

We developed a longitudinal cohort study of FEP patients 16-45 years old, presenting at the emergency units of five psychiatric hospitals across Athens, Greece. Research timeline includes baseline, 1-month and 1-year follow-up. Clinical, genetic, environmental, cognitive and biochemical parameters are measured, using psychometric tools, clinical interviews and laboratory tests. A descriptive analysis of baseline and 1-month assessments was performed including demographic characteristics, family history, medication, clinical picture, traumatic experiences, drug use and cognitive functioning.

RESULTS

During the last 3 years, 130 subjects have been enrolled in the study. Data so far reveal that, despite the severity of baseline presentation, at 1-month the majority (57.4%) met the Andreasen symptom severity criteria for remission, without the time criterion and showed mild functional improvement. Several environmental adversities and poor cognitive performance were identified, which need to be further elaborated.

CONCLUSIONS

Athens FEP Research study is the first gene-environment interaction study in Greece. In this article we introduce the organization and methodological framework of the project, along with its basic initial findings. Future analysis will allow the validation of tractable predictors and risk factors implicated in the development and outcome of psychosis.

Olfactory Influences on Visual Categorization: Behavioral and ERP Evidence

Visual stimuli often dominate nonvisual stimuli during multisensory perception. Evidence suggests higher cognitive processes prioritize visual over nonvisual stimuli during divided attention. Visual stimuli should thus be disproportionally distracting when processing incongruent cross-sensory stimulus pairs. We tested this assumption by comparing visual processing with olfaction, a “primitive” sensory channel that detects potentially hazardous chemicals by alerting attention. Behavioral and event-related brain potentials (ERPs) were assessed in a bimodal object categorization task with congruent or incongruent odor–picture pairings and a delayed auditory target that indicated whether olfactory or visual cues should be categorized. For congruent pairings, accuracy was higher for visual compared to olfactory decisions. However, for incongruent pairings, reaction times (RTs) were faster for olfactory decisions. Behavioral results suggested that incongruent odors interfered more with visual decisions, thereby providing evidence for an “olfactory dominance” effect. Categorization of incongruent pairings engendered a late “slow wave” ERP effect. Importantly, this effect had a later amplitude peak and longer latency during visual decisions, likely reflecting additional categorization effort for visual stimuli in the presence of incongruent odors. In sum, contrary to what might be inferred from theories of “visual dominance,” incongruent odors may in fact uniquely attract mental processing resources during perceptual incongruence.

Neural Evidence of Superior Memory: How to Capture Brain Activities of Encoding Processes Underlying Superior Memory

Relatively little attention has been paid to the neural basis of superior memory despite its potential in providing important insight into efforts to improve memory in the general population or to offset age-related cognitive decline. The current study reports a rare opportunity to reproduce and isolate specific neural activities directly associated with exceptional memory. To capture the brain processes responsible for superior memory, we returned to a laboratory task and analytic approach used to explore the nature of exceptional memory, namely, digit-span task combined with verbal protocol analysis. One participant with average memory received approximately 50 h of digit-span training and the participant's digit-span increased from normative (8 digits) to exceptional (30 digits). Event-related potentials were recorded while the participant's digit span increased from 19 to 30 digits. Protocol analysis allowed us to identify direct behavioral indices of idiosyncratic encoding processes underlying the superior memory performance. EEG indices directly corresponding to the behavioral indices of encoding processes were identified. The results suggest that the early attention-related encoding processes were reflected in theta and delta whereas the later attention-independent encoding processes were reflected in time-domain slow-wave. This fine-grained approach offers new insights into studying neural mechanism mediating superior memory and the cognitive effort necessary to develop it.

Long-term exposure to high altitude attenuates verbal and spatial working memory: Evidence from an event-related potential study

INTRODUCTION

This study aimed to determine the neurocognitive basis underlying the effects of long-term high-altitude (HA) exposure on working memory (WM).

METHODS

Using event-related potentials (ERPs), we compared the performance of an HA group (individuals who had lived at HA for 3 years but were born and raised at low altitude [LA]) to that of an LA group (individuals who had only lived at LA) on verbal and spatial n-back tasks (i.e., 1- and 2-back memory load).

RESULTS

Response accuracy of the HA group was significantly decreased in comparison to the LA group in both the verbal and spatial 2-back tasks. The P2 amplitude was larger in the HA than in the LA group in the spatial, but not the verbal 2-back task. A smaller late-positive potential (LPP) amplitude was found in the HA group in both the verbal and spatial 2-back tasks.

CONCLUSIONS

These results suggest that HA impairs the matching (P2) process in spatial WM tasks and the maintenance (LPP) process in both verbal and spatial WM tasks, indicating that HA had a different effect on verbal and spatial 2-back task performance.

Distress intolerance modulation of neurophysiological markers of cognitive control during a complex go/no-go task

Distress intolerance (DI), a trait-like individual difference reflective of the inability to endure aversive affective states, is relevant to multiple forms of psychopathology, but its relations to theoretically relevant neurobiological systems have received little attention. Altered cognitive control-related neurobiology has been theorized to underlie individual differences in DI, but little empirical work has been conducted. To test this hypothesis, baseline data from a large community sample with elevated high levels of emotional psychopathology and comorbidity was utilized (N = 256). Participants completed a complex go/no-go task while EEG was recorded, and P2, N2, and P3 amplitudes were measured. Based upon prior findings on the relations between these components and response inhibition, a core cognitive control function, we hypothesized that DI would predict reduced no-go N2 and P3 amplitude while controlling for current anxious/depressive symptom severity (i.e., negative affect). Peak amplitudes from the raw data and principal components analysis were used to quantify amplitude of ERP components. Partially consistent with predictions, high DI was independently associated with reduced no-go N2 peak amplitude in the raw ERP data, and was significantly related to a frontal positivity factor in the N2 time window across no-go and go trials. Contrary to predictions, no relations between DI and the P3 were found. Overall, results support the theorized relevance of cognitive control-linked neurobiology to individual differences in tolerance of distress over and above distress severity itself, and suggest specific relations between DI and alterations in early controlled attention/conflict-monitoring but not response inhibition or response inhibition-related sequelae. (PsycINFO Database Record

Attentional responses on an auditory oddball predict false memory susceptibility

Attention and memory are highly integrated processes. Building on prior behavioral investigations, this study assesses the link between individual differences in low-level neural attentional responding and false memory susceptibility on the misinformation effect, a paradigm in which false event memories are induced via misleading post-event information. Twenty-four subjects completed the misinformation effect paradigm after which high-density (256-channel) EEG data was collected as they engaged in an auditory oddball task. Temporal-spatial decomposition was used to extract two attention-related components from the oddball data, the P3b and Classic Slow Wave. The P3b was utilized as an index of individual differences in salient target attentional responding while the slow wave was adopted as an index of variability in task-level sustained attention. Analyses of these components show a significant negative relationship between slow-wave responses to oddball non-targets and perceptual false memory endorsements, suggestive of a link between individual differences in levels of sustained attention and false memory susceptibility. These findings provide the first demonstrated link between individual differences in basic attentional responses and false memory. These results support prior behavioral work linking attention and false memory and highlight the integration between attentional processes and real-world episodic memory.

The Effects of Arousal and Approach Motivated Positive Affect on Cognitive Control. An ERP Study

A growing body of research has demonstrated that affect modulates cognitive control modes such as proactive and reactive control. Several studies have suggested that positive affect decreases proactive control compared to neutral affect. However, these studies only focused on the valence of affect and often omitted two of its components: arousal and approach motivation. Therefore, we designed the present study to test the hypothesis that cognitive control modes would differ as a function of arousal and approach motivated positive affect. In our study, we used an AX-continuous performance task (AX-CPT), commonly used to examine shifts in proactive and reactive control. We also measured P3b, contingent negative variation (CNV), N2 and P3a components of event-related brain potentials (ERPs) as indicators of the use of cognitive control modes. The findings of the present study demonstrated that approach motivated positive affect modified only the P3b and the CNV without effects on the N2 and P3a components. However, arousal induced by pictures modified P3b, CNV and N2 amplitudes. Specifically, the P3b amplitude was larger, and CNV amplitude was less negative in the high than in the low-approach motivated affect. In contrast, the P3b amplitude was larger and both the CNV and N2 amplitudes more negative in low- compared with high-arousal conditions. These ERP results suggest that approach motivated positive affect enhanced proactive control with no effect on reactive control. However, arousal influenced both proactive and reactive control. High arousal decreased proactive control and increased reactive control compared to low arousal. The present study provides novel insights into the relationship between affect, specifically, arousal and approach motivated positive affect and cognitive control modes. In addition, our results help to explain discrepancies found in previous research.

Testing the bottleneck account for post-error slowing beyond the post-error response

The bottleneck account for post-error slowing assumes that cognitive resources are depleted after errors and thus the processing of subsequent events is delayed. To test this, we used a novel speeded-choice task and recorded behavioral measures and ERP (event-related potential) components on five trials following either an erroneous or correct response. We found that participants were slower and less accurate immediately after making an error and that this reduction of performance decayed on the following trials. Moreover, post-correct versus post-error differences in both the visual N1 and the P3 component were found. However, the difference in the P3 component rapidly diminished over time, whereas the differences in the N1 component were still evident in the fourth trial following the erroneous response. The results lay further support to the bottleneck account for post-error slowing and show a combination of early attentional and higher-order processing changes that occur after erroneous responses.

Working Memory Updating Training Improves Mathematics Performance in Middle School Students With Learning Difficulties

Working memory (WM) deficit is considered the key cause of learning difficulties (LDs). Studies have shown that WM is plastic and thus can be improved through training. This positive effect is transferable to fluid intelligence and academic performance. This study investigated whether WM updating ability and academic performance in children with LDs could be improved through WM updating training and explored the effects of this training on the children’s brain activity. We used a running memory task lasting approximately 40 min per day for 28 days to train a group of 23 children with LDs (TLDs group). We also selected two control groups of 22 children with LDs (CLDs group) and 20 children without LDs (normal control [NC] group). The behavioral results of a pretest indicated that WM updating ability and academic performance in the TLDs and CLDs groups were significantly lower than those in the NC group before training. Compared with the CLDs group, the TLDs group exhibited significant performance improvement in a 2-back WM task, as well as in mathematical ability. Event-related potentials (ERPs) results suggested that the amplitudes of N160 (representative of visual recognition) and P300 (representative of updating processing, which is a valid index for updating WM) in the TLDs and CLDs groups were markedly lower than those in the NC group before training. In the TLDs group, these two components increased considerably after training, approaching levels similar to those in the NC group. The results of this study suggest that WM updating training can improve WM updating ability in children with LDs and the training effect can transfer to mathematical performance in such children. Furthermore, the participants’ brain activity levels can exhibit positive changes. This article provides experimental evidence that WM updating training could mitigate the symptoms of LDs to a certain degree.

Cortical oscillations and entrainment in speech processing during working memory load

Neuronal oscillations are thought to play an important role in working memory (WM) and speech processing. Listening to speech in real‐life situations is often cognitively demanding but it is unknown whether WM load influences how auditory cortical activity synchronizes to speech features. Here, we developed an auditory n‐back paradigm to investigate cortical entrainment to speech envelope fluctuations under different degrees of WM load. We measured the electroencephalogram, pupil dilations and behavioural performance from 22 subjects listening to continuous speech with an embedded n‐back task. The speech stimuli consisted of long spoken number sequences created to match natural speech in terms of sentence intonation, syllabic rate and phonetic content. To burden different WM functions during speech processing, listeners performed an n‐back task on the speech sequences in different levels of background noise. Increasing WM load at higher n‐back levels was associated with a decrease in posterior alpha power as well as increased pupil dilations. Frontal theta power increased at the start of the trial and increased additionally with higher n‐back level. The observed alpha–theta power changes are consistent with visual n‐back paradigms suggesting general oscillatory correlates of WM processing load. Speech entrainment was measured as a linear mapping between the envelope of the speech signal and low‐frequency cortical activity (< 13 Hz). We found that increases in both types of WM load (background noise and n‐back level) decreased cortical speech envelope entrainment. Although entrainment persisted under high load, our results suggest a top‐down influence of WM processing on cortical speech entrainment.

Early and late components of EEG delay activity correlate differently with scene working memory performance

Sustained and elevated activity during the working memory delay period has long been considered the primary neural correlate for maintaining information over short time intervals. This idea has recently been reinterpreted in light of findings generated from multiple neural recording modalities and levels of analysis. To further investigate the sustained or transient nature of activity, the temporal-spectral evolution (TSE) of delay period activity was examined in humans with high density EEG during performance of a Sternberg working memory paradigm with a relatively long six second delay and with novel scenes as stimuli. Multiple analyses were conducted using different trial window durations and different baseline periods for TSE computation. Sensor level analyses revealed transient rather than sustained activity during delay periods. Specifically, the consistent finding among the analyses was that high amplitude activity encompassing the theta range was found early in the first three seconds of the delay period. These increases in activity early in the delay period correlated positively with subsequent ability to distinguish new from old probe scenes. Source level signal estimation implicated a right parietal region of transient early delay activity that correlated positively with working memory ability. This pattern of results adds to recent evidence that transient rather than sustained delay period activity supports visual working memory performance. The findings are discussed in relation to synchronous and desynchronous intra- and inter-regional neural transmission, and choosing an optimal baseline for expressing temporal-spectral delay activity change.

SLC2A3 single-nucleotide polymorphism and duplication influence cognitive processing and population-specific risk for attention-deficit/hyperactivity disorder

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) is a common, highly heritable neurodevelopmental disorder with profound cognitive, behavioral, and psychosocial impairments with persistence across the life cycle. Our initial genome-wide screening approach for copy number variants (CNVs) in ADHD implicated a duplication of SLC2A3, encoding glucose transporter-3 (GLUT3). GLUT3 plays a critical role in cerebral glucose metabolism, providing energy for the activity of neurons, which, in turn, moderates the excitatory-inhibitory balance impacting both brain development and activity-dependent neural plasticity. We therefore aimed to provide additional genetic and functional evidence for GLUT3 dysfunction in ADHD.

METHODS

Case-control association analyses of SLC2A3 single-nucleotide polymorphisms (SNPs) and CNVs were conducted in several European cohorts of patients with childhood and adult ADHD (SNP, n = 1,886 vs. 1,988; CNV, n = 1,692 vs. 1,721). These studies were complemented by SLC2A3 expression analyses in peripheral cells, functional EEG recordings during neurocognitive tasks, and ratings of food energy content.

RESULTS

Meta-analysis of all cohorts detected an association of SNP rs12842 with ADHD. While CNV analysis detected a population-specific enrichment of SLC2A3 duplications only in German ADHD patients, the CNV + rs12842 haplotype influenced ADHD risk in both the German and Spanish cohorts. Duplication carriers displayed elevated SLC2A3 mRNA expression in peripheral blood cells and altered event-related potentials reflecting deficits in working memory and cognitive response control, both endophenotypic traits of ADHD, and an underestimation of energy units of high-caloric food.

CONCLUSIONS

Taken together, our results indicate that both common and rare SLC2A3 variation impacting regulation of neuronal glucose utilization and energy homeostasis may result in neurocognitive deficits known to contribute to ADHD risk.

Generalization of Context-Specific Training in Individuals with Mild Cognitive Impairment: An Event-Related Potential Study

Background

This study examined the neural processes associated with the generalization of the effect of context-specific (CS) training to noncontextual situations among individuals with mild cognitive impairment (MCI).

Methods

Fourteen and 16 participants with MCI were randomly allocated to a Chinese calligraphy writing (CW) training or a control group, respectively. The CW participants learned how to write Chinese strokes in a semicursive style to construct characters, tapping on working memory functions. The control group, on the other hand, learned how to use a tablet computer without emphasis on working memory functions. They then performed two 2-back tasks with CS semicursive strokes and non-context-specific (NCS) digits. Event-related electroencephalogram signals were concurrently recorded.

Results

The CW participants had a significantly shorter reaction time in the CS than in the NCS task (p < 0.05). They showed significantly longer latency in working memory updating (N200; t<Sub>11</Sub> = 4.70, p = 0.05) and shorter latency in the evaluation of visual representation (P300; t<Sub>12</Sub> = 4.67; p = 0.05) than the control group when performing the 2-back CS task. Shorter P300 latency was also revealed in the 2-back NCS task (t<Sub>12</Sub> = 5.15, p = 0.041), suggesting a possible generalization of the training effect among the CW participants.

Conclusion

The results suggest that CS working memory is likely to be generalized to NCS domains among individuals with MCI. Future research should extend the scope of the generalization and apply it beyond experimental conditions.

Comparison of the Working Memory Load in N-Back and Working Memory Span Tasks by Means of EEG Frequency Band Power and P300 Amplitude

According to theoretical accounts, both, N-back and complex span tasks mainly require working memory (WM) processing. In contrast, simple span tasks conceptually mainly require WM storage. Thus, conceptually, an N-back task and a complex span task share more commonalities as compared to a simple span task. In the current study, we compared an N-back task, a complex operation span task (Ospan), and a simple digit span task (Dspan) by means of typical WM load-related measures of the Electroencephalogram (EEG) like the parietal alpha and beta frequency band power, the frontal theta frequency band power, and the P300 amplitude, to examine whether these tasks would show commonalities or differences in WM processing-load. We expected that increasing WM-load would generally lead to a decreased alpha and beta frequency band power, an increased theta frequency band power, and a decreased P300 amplitude. Yet, based on the conceptual considerations, we hypothesized that the outcomes of these measures would be more comparable between the N-back and the Ospan as compared to the Dspan. Our hypotheses were partly confirmed. The N-back and the Ospan showed timely more prolonged alpha frequency band power effects as compared to the Dspan. This might indicate higher demands on WM processing in the former two tasks. The theta frequency band power and the P300 amplitude were most pronounced in the N-back task as compared to both span tasks. This might indicate specific demands on cognitive control in the N-back task. Additionally, we observed that behavioral performance measures correlated with changes in EEG alpha power of the N-back and the Ospan, yet not of the Dspan. Taken together, the hypothesized conceptual commonalities between the N-back task and the Ospan (and, for the Dspan, differences) were only partly confirmed by the electrophysiological WM load-related measures, indicating a potential need for reconsidering the theoretical accounts on WM tasks and the value of a closer link to electrophysiological research herein.

Slow Wave Activity Related to Working Memory Maintenance in the N-Back Task

Abstract. Working memory supports our ability to maintain goal-relevant information that guides cognition in the face of distraction or competing tasks. The N-back task has been widely used in cognitive neuroscience to examine the functional neuroanatomy of working memory. Fewer studies have capitalized on the temporal resolution of event-related brain potentials (ERPs) to examine the time course of neural activity in the N-back task. The primary goal of the current study was to characterize slow wave activity observed in the response-to-stimulus interval in the N-back task that may be related to maintenance of information between trials in the task. In three experiments, we examined the effects of N-back load, interference, and response accuracy on the amplitude of the P3b following stimulus onset and slow wave activity elicited in the response-to-stimulus interval. Consistent with previous research, the amplitude of the P3b decreased as N-back load increased. Slow wave activity over the frontal and posterior regions of the scalp was sensitive to N-back load and was insensitive to interference or response accuracy. Together these findings lead to the suggestion that slow wave activity observed in the response-to-stimulus interval is related to the maintenance of information between trials in the 1-back task.

Increasing Working Memory Load Reduces Processing of Cross-Modal Task-Irrelevant Stimuli Even after Controlling for Task Difficulty and Executive Capacity

The classic account of the load theory (LT) of attention suggests that increasing cognitive load leads to greater processing of task-irrelevant stimuli due to competition for limited executive resource that reduces the ability to actively maintain current processing priorities. Studies testing this hypothesis have yielded widely divergent outcomes. The inconsistent results may, in part, be related to variability in executive capacity (EC) and task difficulty across subjects in different studies. Here, we used a cross-modal paradigm to investigate whether augmented working memory (WM) load leads to increased early distracter processing, and controlled for the potential confounders of EC and task difficulty. Twenty-three young subjects were engaged in a primary visual WM task, under high and low load conditions, while instructed to ignore irrelevant auditory stimuli. Demands of the high load condition were individually titrated to make task difficulty comparable across subjects with differing EC. Event-related potentials (ERPs) were used to measure neural activity in response to stimuli presented in both the task relevant modality (visual) and task-irrelevant modality (auditory). Behavioral results indicate that the load manipulation and titration procedure of the primary visual task were successful. ERPs demonstrated that in response to visual target stimuli, there was a load-related increase in the posterior slow wave, an index of sustained attention and effort. Importantly, under high load, there was a decrease of the auditory N1 in response to distracters, a marker of early auditory processing. These results suggest that increased WM load is associated with enhanced attentional engagement and protection from distraction in a cross-modal setting, even after controlling for task difficulty and EC. Our findings challenge the classic LT and offer support for alternative models.

Costs of storing colour and complex shape in visual working memory: Insights from pupil size and slow waves

We investigated the impact of perceptual processing demands on visual working memory of coloured complex random polygons during change detection. Processing load was assessed by pupil size (Exp. 1) and additionally slow wave potentials (Exp. 2). Task difficulty was manipulated by presenting different set sizes (1, 2, 4 items) and by making different features (colour, shape, or both) task-relevant. Memory performance in the colour condition was better than in the shape and both condition which did not differ. Pupil dilation and the posterior N1 increased with set size independent of type of feature. In contrast, slow waves and a posterior P2 component showed set size effects but only if shape was task-relevant. In the colour condition slow waves did not vary with set size. We suggest that pupil size and N1 indicates different states of attentional effort corresponding to the number of presented items. In contrast, slow waves reflect processes related to encoding and maintenance strategies. The observation that their potentials vary with the type of feature (simple colour versus complex shape) indicates that perceptual complexity already influences encoding and storage and not only comparison of targets with memory entries at the moment of testing.

The electrocortical modulation effects of different emotion regulation strategies

The current event-related potential study investigated the modulation effects of different emotion regulation strategies on electrocortical responses. When watching negative or neutral pictures, participants were instructed to perform three tasks: cognitive reappraisal, expressive suppression and passive viewing. We found that negative pictures elicited a larger late positive potential (LPP) than neutral pictures. Moreover, processes involved in strategy also had an effect on LPP amplitude, which was indicated by a larger LPP in reappraisal compared with suppression and viewing tasks when neutral pictures were presented. After the influence of processes on LPP was excluded, results showed that reappraisal effectively decreased the emotion-enhanced LPP than suppression and viewing. The difference in regulatory effect may be determined by the underlying processing mechanism. A larger frontal-central component, N2, was observed in suppression than reappraisal and viewing, which suggested that it involved the processes focusing on behavioral response. While the larger LPP found in reappraisal implicated that it recruited cognitive processes focusing on the picture meaning.

Getting ready for an emotion: specific premotor brain activities for self-administered emotional pictures

Emotional perception has been extensively studied, but only a few studies have investigated the brain activity preceding exposure to emotional stimuli, especially when they are triggered by the subject himself. Here, we sought to investigate the emotional expectancy by means of movement related cortical potentials (MRCPs) in a self-paced task, in which the subjects begin the affective experience by pressing a key. In this experiment, participants had to alternatively press two keys to concomitantly display positive, negative, neutral, and scrambled images extracted from the International Affective Pictures System (IAPS). Each key press corresponded to a specific emotional category, and the experimenter communicated the coupling before each trial so that the subjects always knew the valence of the forthcoming picture. The main results of the present study included a bilateral positive activity in prefrontal areas during expectancy of more arousing pictures (positive and negative) and an early and sustained positivity over occipital areas, especially during negative expectancy. In addition, we observed more pronounced and anteriorly distributed Late Positive Potential (LPPs) components in the emotional conditions. In conclusion, these results show that emotional expectancy can influence brain activity in both motor preparation and stimulus perception, suggesting enhanced pre-processing in the to-be-stimulated areas. We propose that before a predictable emotional stimulus, both appetitive and defensive motivational systems act to facilitate the forthcoming processing of survival-relevant contents by means of an enhancement of attention toward more arousing pictures.

The difference in spatiotemporal dynamics between modus ponens and modus tollens in the Wason selection task: an event-related potential study

High-density, event-related brain potentials (ERPs) were recorded to explore differences in spatiotemporal dynamics between modus ponens (MP) and modus tollens (MT) in the Wason selection task. Results showed that MP elicits a more positive P3b-like component than MT from 400 to 800 ms. MP appeared to occur earlier than MT in various stages of proposition testing, such as stimulus processing and response selection. ERP results showed that MT has a longer duration and more negative later negative component (LNC) than MP at 2,000 ms. This result suggests that MT occupies more cognitive resources than MP in the final stages of proposition testing. The short and small left frontal LNC obtained by MP implies examination of the expectable conclusion, whereas the long and large left frontal LNC elicited by MT may be involved in the retention operation of the card in working memory from the monitoring and inspecting putative conclusion in the later stages of proposition testing.

EEG and MEG: relevance to neuroscience

To understand dynamic cognitive processes, the high time resolution of EEG/MEG is invaluable. EEG/MEG signals can play an important role in providing measures of functional and effective connectivity in the brain. After a brief description of the foundations and basic methodological aspects of EEG/MEG signals, the relevance of the signals to obtain novel insights into the neuronal mechanisms underlying cognitive processes is surveyed, with emphasis on neuronal oscillations (ultra-slow, theta, alpha, beta, gamma, and HFOs) and combinations of oscillations. Three main functional roles of brain oscillations are put in evidence: (1) coding specific information, (2) setting and modulating brain attentional states, and (3) assuring the communication between neuronal populations such that specific dynamic workspaces may be created. The latter form the material core of cognitive functions.

Time-course of cortical networks involved in working memory

Working memory (WM) is one of the most studied cognitive constructs. Although many neuroimaging studies have identified brain networks involved in WM, the time course of these networks remains unclear. In this paper we use dense-array electroencephalography (dEEG) to capture neural signals during performance of a standard WM task, the n-back task, and a blend of principal components analysis and independent components analysis (PCA/ICA) to statistically identify networks of WM and their time courses. Results reveal a visual cortex centric network, that also includes the posterior cingulate cortex, that is active prior to stimulus onset and that appears to reflect anticipatory, attention-related processes. After stimulus onset, the ventromedial prefrontal cortex, lateral prefrontal prefrontal cortex, and temporal poles become associated with the prestimulus network. This second network appears to reflect executive control processes. Following activation of the second network, the cortices of the temporo-parietal junction with the temporal lobe structures seen in the first and second networks re-engage. This third network appears to reflect activity of the ventral attention network involved in control of attentional reorientation. The results point to important temporal features of network dynamics that integrate multiple subsystems of the ventral attention network with the default mode network in the performance of working memory tasks.

Low-arousal speech noise improves performance in N-back task: an ERP study

The relationship between noise and human performance is a crucial topic in ergonomic research. However, the brain dynamics of the emotional arousal effects of background noises are still unclear. The current study employed meaningless speech noises in the n-back working memory task to explore the changes of event-related potentials (ERPs) elicited by the noises with low arousal level vs. high arousal level. We found that the memory performance in low arousal condition were improved compared with the silent and the high arousal conditions; participants responded more quickly and had larger P2 and P3 amplitudes in low arousal condition while the performance and ERP components showed no significant difference between high arousal and silent conditions. These findings suggested that the emotional arousal dimension of background noises had a significant influence on human working memory performance, and that this effect was independent of the acoustic characteristics of noises (e.g., intensity) and the meaning of speech materials. The current findings improve our understanding of background noise effects on human performance and lay the ground for the investigation of patients with attention deficits.

Developmental changes in visuo-spatial working memory in normally developing children: event-related potentials study

OBJECTIVE

Working memory (WM) is very important for normal development. The fronto-parietal neuronal network supporting WM has already been well-studied. Less is known about the cortical activity changes during development of WM. We evaluated the maturation of visual WM network at the electrophysiological level in a group of normally developing children.

METHODS

Multichannel (n=31) event-related potentials (ERP) were measured during a visuo-spatial backmatching task in 69 childrens (6-16 years old). One-backmatching (BM1) and two-backmatching (BM2) tasks were performed. Age-related changes in behavioral parameters (commission and omission errors and reaction times) and ERP parameters (peak amplitudes and latencies) were analyzed between different ages.

RESULTS

Clear improvement in performance from young childhood toward adolescence was seen at the behavioral level: decrease of errors and fastening of reaction times. At the electrophysiological level age-related changes were seen in peak latencies and especially in amplitudes. Different peaks have different dynamics in amplitudes and latencies: early peak amplitude decreased and latency shortened with age, which was not always seen in late peaks. This reflects developmental changes in intensity and speed of WM processing. Later peaks were more clearly seen over the right hemisphere in older children, illustrating hemispheric lateralization in visuo-spatial working memory.

CONCLUSIONS

Our results indicate that not only at the behavioral but also at the electrophysiological level clear age-related dynamics in WM processing can be seen. Furthermore, with ERP we showed that different WM components follow different developmental trajectories.

SIGNIFICANCE

Our work demonstrates that age-related dynamics in intensity and speed of information processing during WM task is reflected in developmental changes in different ERP components. It also states that fronto-parietal visual WM network can be functional even before all its nodes are fully mature.

Neurophysiological pharmacodynamic measures of groups and individuals extended from simple cognitive tasks to more "lifelike" activities

OBJECTIVE

Extend a method to track neurophysiological pharmacodynamics during repetitive cognitive testing to a more complex "lifelike" task.

METHODS

Alcohol was used as an exemplar psychoactive substance. An equation, derived in an exploratory analysis to detect alcohol's EEGs effects during repetitive cognitive testing, was validated in a Confirmatory Study on a new group whose EEGs after alcohol and placebo were recorded during working memory testing and while operating an automobile driving simulator.

RESULTS

The equation recognized alcohol by combining five times beta plus theta power. It worked well (p < .0001) when applied to both tasks in the confirmatory group. The maximum EEG effect occurred 2-2.5 h after drinking (>1 h after peak BAC) and remained at 90% at 3.5-4 h (BAC < 50% of peak). Individuals varied in the magnitude and timing of the EEG effect.

CONCLUSION

The equation tracked the EEG response to alcohol in the Confirmatory Study during both repetitive cognitive testing and a more complex "lifelike" task. The EEG metric was more sensitive to alcohol than several autonomic physiological measures, task performance measures or self-reports.

SIGNIFICANCE

Using EEG as a biomarker to track neurophysiological pharmacodynamics during complex "lifelike" activities may prove useful for assessing how drugs affect integrated brain functioning.

Bipolar disorder ANK3 risk variant effect on sustained attention is replicated in a large healthy population

Independent genome-wide association studies have implicated a common single nucleotide polymorphism within the ANK3 gene (rs10994336) in bipolar disorder (BD) susceptibility, thus establishing rs10994336 marker as a strong candidate predisposing genetic factor for BD. Furthermore, recent findings demonstrate that this variant impacts on cognitive functioning in BD patients, their unaffected relatives, and healthy controls by influencing sustained attention. Here, we aimed to replicate this finding in a large population-based sample of healthy young adults (n=1808). Sustained attention was evaluated using the Continuous Performance Test as in the original study and working memory was assessed with the n-back task. Individuals carrying the BD risk T-allele showed significantly reduced sensitivity in target detection, increased errors of commission, and atypical response latency variability. In addition, we confirmed the lack of an association between the rs10994336 variant and working memory, as well as general intellectual ability, suggesting a specific effect on the Continuous Performance Test performance.

Auditory working memory impairments in individuals at familial high risk for schizophrenia

OBJECTIVES

The search for predictors of schizophrenia has accelerated with a growing focus on early intervention and prevention of psychotic illness. Studying nonpsychotic relatives of individuals with schizophrenia enables identification of markers of vulnerability for the illness independent of confounds associated with psychosis. The goal of these studies was to develop new auditory continuous performance tests (ACPTs) and evaluate their effects in individuals with schizophrenia and their relatives.

METHODS

We carried out two studies of auditory vigilance with tasks involving working memory (WM) and interference control with increasing levels of cognitive load to discern the information-processing vulnerabilities in a sample of schizophrenia patients, and two samples of nonpsychotic relatives of individuals with schizophrenia and controls. Study 1 assessed adults (mean age = 41), and Study 2 assessed teenagers and young adults age 13-25 (M = 19).

RESULTS

Patients with schizophrenia were impaired on all five versions of the ACPTs, whereas relatives were impaired only on WM tasks, particularly the two interference tasks that maximize cognitive load. Across all groups, the interference tasks were more difficult to perform than the other tasks. Schizophrenia patients performed worse than relatives, who performed worse than controls. For patients, the effect sizes were large (Cohen's d = 1.5), whereas for relatives they were moderate (d = ~0.40-0.50). There was no age by group interaction in the relatives-control comparison except for participants <31 years of age.

CONCLUSIONS

Novel WM tasks that manipulate cognitive load and interference control index an important component of the vulnerability to schizophrenia.