Sensitivity of alpha band ERD to individual differences in cognition

Task-irrelevant decorative pictures increase cognitive load during text processing but have no effects on learning or working memory performance: an EEG and eye-tracking study

Decorative pictures (DP) are often used in multimedia task materials and are commonly considered so-called seductive details as they are commonly not task-relevant. Typically, DP result in mixed effects on behavioral performance measures. The current study focused on the effects of DP on the cognitive load during text reading and working memory task performance. The theta and alpha frequency band power of the electroencephalogram (EEG) and pupil dilation served as proxies of cognitive load. The number of fixations, mean fixation durations, and the number of transitions served as proxies of the attentional focus. For both, text reading and n-back working memory tasks, the presence and congruency of DP were manipulated in four task conditions. DP did neither affect behavioral performance nor subjective ratings of emotional-motivational factors. However, in both tasks, DP increased the cognitive load as revealed by the EEG alpha frequency band power and (at least to some extent) by subjective effort ratings. Notably, the EEG alpha frequency band power was a quite reliable and sensitive proxy of cognitive load. Analyzing the EEG data stimulus-locked and fixation-related, the EEG alpha frequency band power revealed a difference in global and local cognitive load. In sum, the current study underlines the feasibility and use of EEG for multimedia research, especially when combined with eye-tracking.

EEG-based neurophysiological indices for expert psychomotor performance - a review

A primary objective of current human neuropsychological performance research is to define the physiological correlates of adaptive knowledge utilization, in order to support the enhanced execution of both simple and complex tasks. Within the present article, electroencephalography-based neurophysiological indices characterizing expert psychomotor performance, will be explored. As a means of characterizing fundamental processes underlying efficient psychometric performance, the neural efficiency model will be evaluated in terms of alpha-wave-based selective cortical processes. Cognitive and motor domains will initially be explored independently, which will act to encapsulate the task-related neuronal adaptive requirements for enhanced psychomotor performance associating with the neural efficiency model. Moderating variables impacting the practical application of such neuropsychological model, will also be investigated. As a result, the aim of this review is to provide insight into detectable task-related modulation involved in developed neurocognitive strategies which support heightened psychomotor performance, for the implementation within practical settings requiring a high degree of expert performance (such as sports or military operational settings).

The Interlinking of Alpha Waves and Visuospatial Cognition in Motor-Based Domains

The manner in which we perceive and respond in accordance to the world is encompassed by our ability to process multimodal input stimuli. In other words, in order to perform any task, especially at a high degree of proficiency, high dependence is placed upon our ability to interact with, interpret, and visualize input stimuli from our environment, known as visuospatial cognition (Chueh et al., 2017). This article will explore and encapsulate the importance of visuospatial cognition, in terms of the link it has with the performance of tasks in various fields, such as artistry, musical performance, and athleticism. Alpha wave investigation will be discussed as a means of both identifying and characterizing the degree of performance within these domains. Findings from this investigation may be used as a modality to optimize performance in the explored domains (e.g., with Neurofeedback techniques). The limitations of using Electroencephalography (EEG) to support the enhancement of this task performance and the recommendations to elicit further research, will also be explored.

Reliability of MUSE 2 and Tobii Pro Nano at capturing mobile application users' real-time cognitive workload changes

Introduction

Despite the importance of cognitive workload in examining the usability of smartphone applications and the popularity of smartphone usage globally, cognitive workload as one attribute of usability tends to be overlooked in Human-Computer Interaction (HCI) studies. Moreover, limited studies that have examined the cognitive workload aspect often measured some summative workloads using subjective measures (e.g., questionnaires). A significant limitation of subjective measures is that they can only assess the overall, subject-perceived cognitive workload after the procedures/tasks have been completed. Such measurements do not reflect the real-time workload fluctuation during the procedures. The reliability of some devices on a smartphone setting has not been thoroughly evaluated.

Methods

This study used mixed methods to empirically study the reliability of an eye-tracking device (i.e., Tobii Pro Nano) and a low-cost electroencephalogram (EEG) device (i.e., MUSE 2) for detecting real-time cognitive workload changes during N-back tasks.

Results

Results suggest that the EEG measurements collected by MUSE 2 are not very useful as indicators of cognitive workload changes in our setting, eye movement measurements collected by Tobii Pro Nano with mobile testing accessory are useful for monitoring cognitive workload fluctuations and tracking down interface design issues in a smartphone setting, and more specifically, the maximum pupil diameter is the preeminent indicator of cognitive workload surges.

Discussion

In conclusion, the pupil diameter measure combined with other subjective ratings would provide a comprehensive user experience assessment of mobile applications. They can also be used to verify the successfulness of a user interface design solution in improving user experience.

Power Spectrum and Connectivity Analysis in EEG Recording during Attention and Creativity Performance in Children

The present research aims at examining the power spectrum and exploring functional brain connectivity/disconnectivity during concentration performance, as measured by the d2 test of attention and creativity as measured by the CREA test in typically developing children. To this end, we examined brain connectivity by using phase synchrony (i.e., phase locking index (PLI) over the EEG signals acquired by the Emotiv EPOC neuroheadset in 15 children aged 9- to 12-years. Besides, as a complement, a power spectrum analysis of the acquired signals was performed. Our results indicated that, during d2 Test performance there was an increase in global gamma phase synchronization and there was a global alpha and theta band desynchronization. Conversely, during CREA task, power spectrum analysis showed a significant increase in the delta, beta, theta, and gamma bands. Connectivity analysis revealed marked synchronization in theta, alpha, and gamma. These findings are consistent with other neuroscience research indicating that multiple brain mechanisms are indeed involved in creativity. In addition, these results have important implications for the assessment of attention functions and creativity in clinical and research settings, as well as for neurofeedback interventions in children with typical and atypical development.

Oscillatory electroencephalographic patterns of arithmetic problem solving in fourth graders

Numerous studies have identified neurophysiological correlates of performing arithmetic in adults. For example, oscillatory electroencephalographic (EEG) patterns associated with retrieval and procedural strategies are well established. Whereas fact retrieval has been linked to enhanced left-hemispheric theta ERS (event-related synchronization), procedural strategies are accompanied by increased bilateral alpha ERD (event-related desynchronization). It is currently not clear if these findings generalize to children. Our study is the first to investigate oscillatory EEG activity related to strategy use and arithmetic operations in children. We assessed ERD/ERS correlates of 31 children in fourth grade (aged between nine and ten years) during arithmetic problem solving. We presented multiplication and subtraction problems, which children solved with fact retrieval or a procedure. We analyzed these four problem categories (retrieved multiplications, retrieved subtractions, procedural multiplications, and procedural subtractions) in our study. In summary, we found similar strategy-related patterns to those reported in previous studies with adults. That is, retrieval problems elicited stronger left-hemispheric theta ERS and weaker alpha ERD as compared to procedural problems. Interestingly, we observed neurophysiological differences between multiplications and subtractions within retrieval problems. Although there were no response time or accuracy differences, retrieved multiplications were accompanied by larger theta ERS than retrieved subtractions. This finding could indicate that retrieval of multiplication and subtraction facts are distinct processes, and/or that multiplications are more frequently retrieved than subtractions in this age group.

Decreased Event-Related Desynchronization of Mental Rotation Tasks in Young Tibetan Immigrants

The present study aimed to explore the cortical activity underlying mental rotation in high-altitude immigrants via the event-related desynchronization (ERD), the electroencephalogram time–frequency analysis, and source localization based on electroencephalographic data. When compared with the low-altitude individuals, the reaction time of mental rotation tasks was significantly slower in immigrants who had lived in high-altitude areas for 3 years. The time–frequency analysis showed that the alpha ERD and the beta ERD within the time window (400–700 ms) were decreased during the mental rotation tasks in these immigrants. The decreased ERD was observed at the parietal–occipital regions within the alpha band and at the central–parietal regions within the beta band. The decreased ERD might embody the sensorimotor-related cortical activity from hypoxia, which might be involved in cognitive control function in high-altitude immigrants, which provided insights into the neural mechanism of spatial cognition change on aspect of embodied cognition due to high-altitude exposure.

Clustering and switching in divergent thinking: Neurophysiological correlates underlying flexibility during idea generation

EEG alpha synchronization, especially in posterior parietal cortical regions of the right hemisphere, is indicative of high internal processing demands that are typically involved in divergent thinking (DT). During the course of DT, as ideation proceeds, ideas tend to become more creative, being more likely to be drawn from new conceptual categories through the use of the cognitive mechanism of flexibility. The present study investigated whether EEG alpha synchronization can be modulated by flexibility in DT by comparing cortical activation patterns during the switch of category (switching) and the stay in the same category (clustering). Twenty participants were required to generate alternative uses of everyday objects during EEG recording. Differential results were specifically found in the lower alpha band (8-10 Hz): whereas clustering showed synchronization typically lateralized in the right posterior parietal areas, switching induced posterior parietal synchronization over both right and left hemispheres. These findings indicate that the two distinct cognitive mechanisms subsuming flexibility (switching and clustering) are associated with a different hemispheric modulation of lower alpha activity, as switching, in comparison to clustering, is related to higher power in the lower alpha band over the left hemisphere. Switching in comparison to clustering may thus require a larger investment of cognitive resources due to the exploratory process of moving from one semantic conceptual category to another in the course of creative ideation.

The effects of visual distractors on cognitive load in a motor imagery brain-computer interface

A brain-computer interface (BCI) is a system that translates neural activity into a practical output. Its functionality, therefore, depends not only on the computer itself, but also on the cognitive system of the user. Distractors have the potential to capture attention, increase cognitive load, and may therefore impact BCI use. The purpose of the current study is to determine the effects of small visual distractors on the cognitive load of users of a motor imagery-BCI, and to examine whether these distractor-mediated effects can be improved by modifying the task interface. Sixteen typically-developed participants completed two sessions of online motor imagery to control an EEG-BCI, under conditions of no distractors, visual distractors, and cognitive strategies (intended to mitigate cognitive load) amid distractors. Cognitive load for each session was assessed through both a ratio of theta to alpha power and the NASA-Task Load Index (NASA-TLX). Task-irrelevant visual stimuli were found to significantly increase the objective measure of cognitive load, particularly for parietal channels. Subjective cognitive load as indexed by the NASA-TLX was predictive of a decrease in BCI performance for participants with below 0.75 classification accuracy (R² = 0.32, p < 0.001), which may indicate a differential susceptibility to changes in workload for "low"-performing participants. Quantifying and addressing the increased cognitive load imparted by distractors on BCI users can aid in the future applicability of the technology in real-world settings.

Effect of Complexity on Frontal Event Related Desynchronisation in Mental Rotation Task

A complexity (orientation and shape of stimuli) in the mental rotation (MR) task often affects reaction time (RT) and response accuracy, but the nature of such reflections in neuroscientific research is commonly undocumented. A number of studies have explored the effect of complexity and subsequently noted down the differences in performance. However, a few studies explored complexity (in the term of angular disparity) and cognitive strategies with respect to correct responses only. In contrast, the present study investigated frontal alpha desynchronization with reference to the complexity and proportions of correct and incorrect responses. Behavioral and neurophysiological responses were investigated to understand the switching between strategies (Analytic vs. Holistic). Results showed longer response time with respect to increased complexity. Frontal alpha desynchronization increased for difficult trials and incorrect responses, suggesting a higher utilization of cognitive resources at the frontal region during the MR task. Higher left frontal desynchronization reflected a trading off between strategies for difficult trials. Taken together, these findings suggest that the effect of stimuli complexity is more nuanced than implied by a simple hemispheric dichotomy for frontal cortex and discuss possible future directions to better understand the multitudinous brain mechanisms involved in MR.

Unsuccessful reduction of high-frequency alpha activity during cognitive activation in schizophrenia

AIMS

Electroencephalogram (EEG) alpha activity during resting state reflects the 'readiness' of an individual to respond to the environment; this includes the performance of cognitive processes. Alpha activity is reported to be attenuated in schizophrenia (SCZ). Understanding the interaction between alpha activity during rest and when cognitively engaged may provide insights into the neural circuitry, which is dysfunctional in SCZ. This study investigated the changes of alpha activity between resting state and cognitive engagement in SCZ patients.

METHODS

Thirty-four SCZ patients and 29 healthy controls (HC) were recruited. EEG was performed in the resting state and during an auditory P300 task. All experimental procedures followed the relevant institutional guidelines and regulations.

RESULTS

In SCZ, high-frequency alpha activity was reduced in the resting state. High-frequency alpha source density was decreased in both the resting-state and a P300 task condition in patients, compared to HC. HC, but not SCZ patients, showed a reduction in high-frequency alpha source density during the P300 task compared to the resting state. The negative correlation between high-frequency alpha source density in the resting state and positive symptoms was significant.

CONCLUSIONS

High-frequency alpha activity in SCZ patients and its unsuccessful reduction during cognitive processing may be biological markers of SCZ.

Evaluation of a Sound Quality Visual Feedback System for Bow Learning Technique in Violin Beginners: An EEG Study

Current music technologies can assist in the process of learning to play a musical instrument and provide objective measures for evaluating the improvement of music students in concrete music tasks. In this paper, we investigated the effects of a sound quality visual feedback system (SQVFS) in violin learning. In particular, we studied the EEG activity of a group of participants with no previous violin playing experience while they learned to produce a stable sound (regarding pitch, dynamics, and timbre) in order to find motor learning biomarkers in a music task. Eighteen subjects with no prior experience in violin playing were divided into two groups: participants in the first group (experimental group, N = 9) practiced with instructional videos and offline feedback from the SQVFS provided in alternation with their performance, while participants in a second group (control group, N = 9) practiced with the instructional videos only. A third group of violin experts (players with more than 6 years of experience) performed the same task for comparative purposes (N = 7). All participants were asked to perform 20 trials (4 blocks of 5 trials) consisting of a violin bowing exercise while their EEG activity and their produced sound was recorded. Significant sound quality improvements along the session were found in all participants with the exception of participants in the expert group. In addition, participants in the experimental group showed increased interest in the learning process and significant improvement after the second block not present in the control group. A significant correlation between the levels of frontal gamma band power and the sound improvement along the task was found in both the experimental and control group. This result is consistent with the temporal binding model which associates gamma band power with the role of integrating (binding) information processed in distributed cortical areas. Task complexity demands more cognitive resources, more binding and thus, gamma band power enhancement, which may be reduced as the demanded task begins to be automated as it is likely to be the case in both beginners groups.

Creative ways to well-being: Reappraisal inventiveness in the context of anger-evoking situations

Neuroscientific studies in the field of creativity mainly focused on tasks drawing on basic verbal divergent thinking demands. This study took a step further by investigating brain mechanisms in response to other types of creative behavior, involving more "real-life" creativity demands in the context of emotion regulation and well-being. Specifically, functional patterns of EEG alpha activity were investigated while participants were required to generate as many and as different ways as possible to reappraise presented anger-eliciting situations in a manner that reduces their anger. Cognitive reappraisal involves some of the same cognitive processes as in conventional verbal creativity tasks, inasmuch as it requires an individual to inhibit or disengage from an emotional event, to shift attention between different perspectives, and to flexibly adopt new solutions. To examine whether alpha oscillations during cognitive reappraisal are different from those during conventional creative ideation, the EEG was also assessed during performance of the Alternative Uses task, requiring individuals to generate as many and as original uses of an object as possible. While cognitive reappraisal was associated with a similar pattern of alpha power as observed in conventional verbal creative ideation, the former yielded significantly stronger alpha power increases at prefrontal sites, along with lower alpha increases at more posterior cortical sites, indicating higher cognitive control and less spontaneous imaginative thought processes in the generation of effective strategies to regulate an ongoing negative emotional state.

Individual differences in oscillatory brain activity in response to varying attentional demands during a word recall and oculomotor dual task

Every day, we face situations that involve multi-tasking. How our brain utilizes cortical resources during multi-tasking is one of many interesting research topics. In this study, we tested whether a dual-task can be differentiated in the neural and behavioral responses of healthy subjects with varying degree of working memory capacity (WMC). We combined word recall and oculomotor tasks because they incorporate common neural networks including the fronto-parietal (FP) network. Three different types of oculomotor tasks (eye fixation, Fix-EM; predictive and random smooth pursuit eye movement, P-SPEM and R-SPEM) were combined with two memory load levels (low-load: five words, high-load: 10 words) for a word recall task. Each of those dual-task combinations was supposed to create varying cognitive loads on the FP network. We hypothesize that each dual-task requires different cognitive strategies for allocating the brain's limited cortical resources and affects brain oscillation of the FP network. In addition, we hypothesized that groups with different WMC will show differential neural and behavioral responses. We measured oscillatory brain activity with simultaneous MEG and EEG recordings and behavioral performance by word recall. Prominent frontal midline (FM) theta (4-6 Hz) synchronization emerged in the EEG of the high-WMC group experiencing R-SPEM with high-load conditions during the early phase of the word maintenance period. Conversely, significant parietal upper alpha (10-12 Hz) desynchronization was observed in the EEG and MEG of the low-WMC group experiencing P-SPEM under high-load conditions during the same period. Different brain oscillatory patterns seem to depend on each individual's WMC and varying attentional demands from different dual-task combinations. These findings suggest that specific brain oscillations may reflect different strategies for allocating cortical resources during combined word recall and oculomotor dual-tasks.

Patients with mild cognitive impairment have an abnormal upper-alpha event-related desynchronization/synchronization (ERD/ERS) during a task of temporal attention

There are several evidences indicating that an impairment in attention-executive functions is present in prodromal Alzheimer's disease and predict future global cognitive decline. In particular, the issue of temporal orienting of attention in patients with mild cognitive impairment (MCI) due to Alzheimer's disease has been overlooked. The present research aimed to explore whether subtle deficits of cortical activation are present in these patients early in the course of the disease. We studied the upper-alpha event-related synchronization/desynchronization phenomenon during a paradigm of temporal orientation of attention. MCI patients (n = 27) and healthy elderly controls (n = 15) performed a task in which periodically omitted tones had to be predicted and their virtual onset time had to be marked by pressing a button. Single-trial responses were measured, respectively, before and after the motor response. Then, upper-alpha responses were compared to upper-alpha power during eyes-closed resting state. The time course of the task was characterized by two different behavioral conditions: (1) a pre-event epoch, in which the subject awaited the virtual onset of the omitted tone, (2) a post-event epoch (after button pressing), in which the subject was in a post-motor response condition. The principal findings are: (1) during the waiting epoch, only healthy elderly had an upper-alpha ERD at the level of both temporal and posterior brain regions; (2) during the post-motor epoch, the aMCI patients had a weaker upper-alpha ERS on prefrontal regions; (3) only healthy elderly showed a laterality effect: (a) during the waiting epoch, the upper-alpha ERD was greater at the level of the right posterior-temporal lead; during the post-motor epoch, the upper alpha ERS was greater on the left prefrontal lead. The relevance of these findings is that the weaker upper-alpha response observed in aMCI patients is evident even if the accuracy of the behavioral performance (i.e., button pressing) is still spared. This abnormal upper-alpha response might represent an early biomarker of the attention-executive network impairment in MCI due to Alzheimer's disease.

Oscillatory EEG correlates of arithmetic strategies: a training study

There has been a long tradition of research on mathematics education showing that children and adults use different strategies to solve arithmetic problems. Neurophysiological studies have recently begun to investigate the brain correlates of these strategies. The existing body of data, however, reflect static end points of the learning process and do not provide information on how brain activity changes in response to training or intervention. In this study, we explicitly address this issue by training participants in using fact retrieval strategies. We also investigate whether brain activity related to arithmetic fact learning is domain-specific or whether this generalizes to other learning materials, such as the solution of figural-spatial problems. Twenty adult students were trained on sets of two-digit multiplication problems and figural-spatial problems. After the training, they were presented with the trained and untrained problems while their brain activity was recorded by means of electroencephalography (EEG). In both problem types, the training resulted in accuracies over 90% and significant decreases in solution times. Analyses of the oscillatory EEG data also revealed training effects across both problem types. Specifically, we observed training-related activity increases in the theta band (3-6 Hz) and decreases in the lower alpha band (8-10 Hz), especially over parietooccipital and parietal brain regions. These results provide the first evidence that a short-term fact retrieval training results in significant changes in oscillatory EEG activity. These findings further corroborate the role of the theta band in the retrieval of semantic information from memory and suggest that theta activity is sensitive to fact retrieval not only in mental arithmetic but also in other domains.

Action-related semantic content and negation polarity modulate motor areas during sentence reading: an event-related desynchronization study

Our study evaluated motor cortex involvement during silent reading of sentences referring to hand actions. We aimed at defining whether sentential polarity (affirmative vs. negative) would modulate motor cortex activation using the event-related desynchronization (ERD) analysis of the mu rhythm. Eleven healthy volunteers performed a reading task involving 160 sentences (80 affirmative: 40 hand-related, 40 abstract; 80 negative: 40 hand-related, 40 abstract). After reading each sentence, subjects had to decide whether the verb was high or low frequency in Italian. Electroencephalographic (EEG) activity was recorded with 32 surface electrodes and mu ERD analyses were performed for each subject. Hand-action related sentences induced a greater mu ERD over the left premotor and motor hand areas compared to abstract sentences. Mu ERD was greater and temporally delayed when the hand-related verbs were presented in the negative versus affirmative form. As predicted by the "embodied semantic" theory of language understanding, motor areas were activated during sentences referring to hand actions. In addition, motor cortex activation was larger for negative than affirmative motor sentences, a finding compatible with the hypothesis that comprehension is more demanding in the specific case of motor content negation.

Gamma oscillatory activity in relation to memory ability in older adults

Human gamma-band activity (GBA) is widely reported to reflect memory processing. Recent studies suggest that GBA is associated with behavioral performance in memory tasks, but it is not clear whether gamma oscillations are related to individual differences in memory ability. To examine this issue, we recruited participants with low memory ability (mild cognitive impairment, or MCI; n=16) as well as age-, education-, and sex-matched controls (n=19) for a study involving a spatial delayed match to sample (DMTS) task. We recorded EEG during task performance and analyzed gamma oscillation changes during the memory maintenance phase of the task. Gamma event-related desynchronization was stronger in the control group than in the MCI group in the mid-frontal area, and mean GBA in this area correlated with clinical memory measures as well as behavioral performance on the DMTS task. These findings suggest that gamma oscillations not only reflect brain activity related to memory processes, but also vary with the memory ability of individuals.

EEG alpha synchronization is related to top-down processing in convergent and divergent thinking

Synchronization of EEG alpha activity has been referred to as being indicative of cortical idling, but according to more recent evidence it has also been associated with active internal processing and creative thinking. The main objective of this study was to investigate to what extent EEG alpha synchronization is related to internal processing demands and to specific cognitive process involved in creative thinking. To this end, EEG was measured during a convergent and a divergent thinking task (i.e., creativity-related task) which once were processed involving low and once involving high internal processing demands. High internal processing demands were established by masking the stimulus (after encoding) and thus preventing further bottom-up processing. Frontal alpha synchronization was observed during convergent and divergent thinking only under exclusive top-down control (high internal processing demands), but not when bottom-up processing was allowed (low internal processing demands). We conclude that frontal alpha synchronization is related to top-down control rather than to specific creativity-related cognitive processes. Frontal alpha synchronization, which has been observed in a variety of different creativity tasks, thus may not reflect a brain state that is specific for creative cognition but can probably be attributed to high internal processing demands which are typically involved in creative thinking.

Neurophysiological evidence for the validity of verbal strategy reports in mental arithmetic

Behavioral research has shown that arithmetic problems (e.g., 6+2=) are solved with various strategies, which can be inferred from the size of the presented problems or from trial-by-trial verbal strategy reports. The validity of these verbal strategy reports, however, has been repeatedly questioned. In the present electroencephalography study, we compared the association of both approaches with the oscillatory brain responses during arithmetic problem solving. Nineteen adults solved small and large addition and subtraction problems and indicated the applied strategy (fact retrieval vs. procedure use) on a trial-by-trial basis by means of verbal strategy reports. Analysis of event-related (de-)synchronization (ERS/ERD) in theta and alpha frequencies revealed a general convergence of verbal strategy reports and the problem size approach, with fact retrieval being accompanied by higher left-hemispheric theta ERS, and procedural strategies being reflected in higher widespread ERD in the lower alpha band and bilateral parietooccipital ERD in the upper alpha band. A direct comparison of the neurophysiological data from both approaches suggests a higher sensitivity of verbal strategy reports to problem solving strategies applied in mental arithmetic, particularly for large problems. Taken together, the current data provide the first neurophysiological evidence for the validity of verbal strategy reports.

The sleep EEG as a marker of intellectual ability in school age children

STUDY OBJECTIVES

To investigate the within-subject stability in the sleep EEG and the association between the sleep EEG and intellectual abilities in 9- to 12-year-old children.

DESIGN

Intellectual ability (WISC-IV, full scale, fluid, and verbal IQ, working memory, speed of processing) were examined and all-night polysomnography was performed (2 nights per subject).

SETTING

Sleep laboratory.

PARTICIPANTS

Fourteen healthy children (mean age 10.5 ± 1.0 years; 6 girls).

MEASUREMENTS AND RESULTS

Spectral analysis was performed on artifact-free NREM sleep epochs (C3/A2). To determine intra-individual stability and inter-individual variability of the sleep EEG, power spectra were used as feature vectors for the estimation of Euclidean distances, and intraclass correlation coefficients (ICC) were calculated for the 2 nights. Sleep spindle peaks were identified for each individual and individual sigma band power was determined. Trait-like aspects of the sleep EEG were observed for sleep stage variables and spectral power. Within-subject distances were smaller than between-subject distances and ICC values ranged from 0.72 to 0.96. Correlations between spectral power in individual frequency bins and intelligence scores revealed clusters of positive associations in the alpha, sigma, and beta range for full scale IQ, fluid IQ, and working memory. Similar to adults, sigma power correlated with full scale (r = 0.67) and fluid IQ (r = 0.65), but not with verbal IQ. Spindle peak frequency was negatively related to full scale IQ (r = -0.56).

CONCLUSIONS

The sleep EEG during childhood shows high within-subject stability and may be a marker for intellectual ability.

Oscillatory EEG correlates of arithmetic strategy use in addition and subtraction

Adults use different strategies in mental arithmetic. For example, they directly retrieve the answer from memory or calculate by means of procedural strategies. Despite growing insight into the hemodynamic and electrophysiological correlates of these strategies, the functional changes in the oscillatory brain dynamics during the use of these strategies remain unknown. In the present high-resolution electroencephalography (EEG) study, we analysed event-related synchronisation (ERS) and desynchronisation (ERD) in the theta and alpha bands while participants solved addition and subtraction problems, which displayed a high probability of retrieval or procedural strategy use. Findings revealed that arithmetic fact retrieval is reflected in left-hemispheric ERS in the theta band, whereas the application of procedural strategies is accompanied by bilateral parietooccipital ERD in the alpha band. The topographical and frequency specificity of the strategy effects provides a start for the development of electrophysiological indices of strategy use in arithmetic.

The creative brain: investigation of brain activity during creative problem solving by means of EEG and FMRI

Cortical activity in the EEG alpha band has proven to be particularly sensitive to creativity-related demands, but its functional meaning in the context of creative cognition has not been clarified yet. Specifically, increases in alpha activity (i.e., alpha synchronisation) in response to creative thinking can be interpreted in different ways: As a functional correlate of cortical idling, as a sign of internal top-down activity or, more specifically, as selective inhibition of brain regions. We measured brain activity during creative thinking in two studies employing different neurophysiological measurement methods (EEG and fMRI). In both studies, participants worked on four verbal tasks differentially drawing on creative idea generation. The EEG study revealed that the generation of original ideas was associated with alpha synchronisation in frontal brain regions and with a diffuse and widespread pattern of alpha synchronisation over parietal cortical regions. The fMRI study revealed that task performance was associated with strong activation in frontal regions of the left hemisphere. In addition, we found task-specific effects in parietotemporal brain areas. The findings suggest that EEG alpha band synchronisation during creative thinking can be interpreted as a sign of active cognitive processes rather than cortical idling.

Abnormally high EEG alpha synchrony during working memory maintenance in twins discordant for schizophrenia

BACKGROUND

The present analyses aimed to test the prediction that schizophrenia patients and their non-schizophrenic co-twins would display reduced efficiency of the neurocognitive mechanisms subserving active maintenance of spatial information in working memory.

METHODS

Upper alpha frequency band EEG event-related desynchronization and synchronization (ERD/ERS) were calculated as percent changes in power relative to an inter-trial baseline across 4 memory loads in a spatial delayed-response task.

RESULTS

During the delay, the diagnostic groups showed equivalent ERD/ERS activity over posterior scalp regions at the lowest memory load; however, as memory load increased, patients, and to an intermediate degree, their non-schizophrenic co-twins (monozygotic and dizygotic pairs collapsed together), showed significantly greater increases in ERD/ERS amplitude as compared with controls.

CONCLUSIONS

These findings demonstrate abnormally increased ERD/ERS amplitudes with increasing memory load in patients with schizophrenia and their co-twins, consistent with inefficiency of the neurocognitive mechanisms supporting active maintenance of information across a delay.