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Cognitive control allows to flexibly guide behaviour in a complex and ever-changing environment. It is supported by theta band (4-7 Hz) neural oscillations that coordinate distant neural populations. However, little is known about the precise neural mechanisms permitting such flexible control. Most research has focused on theta amplitude, showing that it increases when control is needed, but a second essential aspect of theta oscillations, their peak frequency, has mostly been overlooked. Here, using computational modelling and behavioural and electrophysiological recordings, in three independent datasets, we show that theta oscillations adaptively shift towards optimal frequency depending on task demands. We provide evidence that theta frequency balances reliable set-up of task representation and gating of task-relevant sensory and motor information and that this frequency shift predicts behavioural performance. Our study presents a mechanism supporting flexible control and calls for a reevaluation of the mechanistic role of theta oscillations in adaptive behaviour. Senoussi et al. present modelling, behavioural and neural evidence that frontal theta oscillations (4-7 Hz) shift their peak frequency in response to task demands to support flexible task implementation.

Objective Studies of the effect of valproate (VPA) on the background EEG have shown varying results. Therefore, we compared the effect of VPA and levetiracetam (LEV) on the EEG alpha peak frequency (APF). Methods We retrospectively examined the APF in resting-state EEG of patients undergoing inpatient video-EEG monitoring (VEM) during withdrawal of VPA or LEV. We assessed APF trends by computing linear fits across individual patients’ APF as a function of consecutive days, and correlated the APF and daily antiseizure medication (ASM) doses on a single-patient and group level. Results The APF in the VPA-group significantly increased over days with falling VPA doses (p = 0.005, n = 13), but did not change significantly in the LEV-group (p = 0.47, n = 18). APF correlated negatively with daily ASM doses in the VPA-group (average of r = −0.74 ± 0.12 across patients, p = 0.0039), but not in the LEV-group (average of r = −0.17 ± 0.18 across patients, p = 0.4072). Conclusions Our results suggest that VPA treatment slows the APF. This APF reduction correlates with the daily dose of VPA and is not present in LEV treatment. Significance Our study identifies a VPA-related slowing of the APF even in patients without electroencephalographic or overt clinical signs of encephalopathy.

Background Cue-reactivity is the array of responses that smokers exhibit when exposed to conditioned and contextual stimuli previously associated to substance use. The difficulty to experimentally recreate the complexity of smokers’ spatial experience and context requires more ecological models. Virtual reality (VR) creates a state of immersion close to reality allowing controlled assessments of behavioral responses. To date, no studies investigated brain activation associated to smoking cue-reactivity in VR using electroencephalography (EEG). Aims To investigate whether a VR cue-reactivity paradigm (a) may increase smoking craving, (b) is feasible with EEG recording, and (c) induces craving levels associated to EEG desynchronization. Methods Smokers (N = 20) and non-smokers (N = 20) were exposed to neutral and smoking-related VR scenarios, without and with smoking conditioned stimuli, respectively. EEG was recorded from occipital and parietal leads throughout the sessions to assess alpha band desynchronization. Smoking and food craving and presence visual analogue scales (VAS) were assessed during the session. Results To be smoker, but not non-smoker, significantly influenced smoking craving VAS induced by smoking cue VR but not by neutral VR. No significant food craving changes was observed during the VR sessions. The new finding was that EEG alpha band power in posterior leads was significantly increased by the smoking context scenario only in smokers, and that the degree of smoking (i.e., heavy vs. light) was significantly associated to this neurophysiological measure. Conclusions This study demonstrated, for the first time, the feasibility of EEG recording in a VR setting, suggesting that EEG desynchronization may be a neurophysiological marker of smoking cue-reactivity.

Objective Chronic pain studies investigating the ability to detect sensory processing differences related to thalamic gating using electroencephalographic (EEG) alpha have yielded conflicting results. Alpha’s basic psychometric properties in pain populations requires further study. The present study reports on the test–retest reliability and internal consistency of EEG alpha power in older adults with chronic knee pain. Methods Repeated EEG alpha power measurements were taken of older adults (N = 31) with chronic knee pain across two sessions separated by a ten-day period associated with a pilot clinical trial study. Recordings included resting periods (eyes open and eyes closed) as well as periods involving a pain management activity. Results Most single alpha-power measures and all within-participant averages of alpha obtained within a session showed high internal consistency (Cronbach’s α > 0.7) and satisfactory-to-excellent re-test reliability (Pearson’s rs > 0.6) of both alpha power and alpha blocking (eyes closed minus eyes open) across repeated conditions. Conclusions EEG alpha power seems mostly reliable and consistent, particularly when participants’ eyes are closed, after a period of habituation, and when alpha measures are averaged as within-participant estimates. Significance This analysis suggests that within-subject averages of EEG alpha are the most reliable for developing indices of chronic knee pain.

Objective Global EEG alpha activity is negatively correlated with skin conductance level (SCL), supporting alpha as an inverse marker of arousal. Frequency Principal Components Analysis (f-PCA) of resting EEG amplitude spectra has demonstrated natural components in the alpha band of healthy persons. This is a preliminary exploration of whether such components differ with arousal, possibly underpinning the anomalous ADHD hypoarousal link to reduced alpha. Method Twenty-seven right-handed undergraduate students participated in three 2 minute blocks of resting eyes-open/closed EEG and SCL: EO1, EC, EO2. For each condition, mean EEG spectra were submitted to separate f-PCAs. Results The inverse alpha/SCL relationship was confirmed for band amplitudes. EO had two alpha components; both correlated negatively with SCL. EC alpha contained four components, but only one had a substantial negative correlation with SCL; two had no relationship, suggesting natural alpha components with different non-arousal functionality in EC. Conclusion Some alpha components in both EC and EO reflect arousal, with other non-arousal components in EC. Our f-PCA approach offers insight into previously-noted alpha anomalies in disorders such as ADHD. Significance This proof of concept demonstration in typical participants may provide the basis for a new research effort in clinical disorders involving atypical arousal patterns.

In this preregistered study (https://osf.io/s4rm9) we investigated the behavioural and neurological [electroencephalography; alpha (attention) and theta (effort)] effects of dynamic non-predictive social and non-social cues on working memory. In a virtual environment realistic human-avatars dynamically looked to the left or right side of a table. A moving stick served as a non-social control cue. Kitchen items were presented in the valid cued or invalid un-cued location for encoding. Behavioural findings showed a similar influence of the cues on working memory performance. Alpha power changes were equivalent for the cues during cueing and encoding, reflecting similar attentional processing. However, theta power changes revealed different patterns for the cues. Theta power increased more strongly for the non-social cue compared to the social cue during initial cueing. Furthermore, while for the non-social cue there was a significantly larger increase in theta power for valid compared to invalid conditions during encoding, this was reversed for the social cue, with a significantly larger increase in theta power for the invalid compared to valid conditions, indicating differences in the cues’ effects on cognitive effort. Therefore, while social and non-social attention cues impact working memory performance in a similar fashion, the underlying neural mechanisms appear to differ.

Our recent study demonstrated that prefrontal transcranial photobiomodulation (tPBM) with 1064-nm laser enables significant changes in EEG rhythms, but these changes might result from the laser-induced heat rather than tPBM. This study hypothesized that tPBM-induced and heat-induced alterations in EEG power topography were significantly distinct. We performed two sets of measurements from two separate groups of healthy humans under tPBM (n = 46) and thermal stimulation (thermo_stim; n = 11) conditions. Each group participated in the study twice under true and respective sham stimulation with concurrent recordings of 64-channel EEG before, during, and after 8-min tPBM at 1064 nm or thermo_stim with temperature of 33–41 °C, respectively. After data preprocessing, EEG power spectral densities (PSD) per channel per subject were quantified and normalized by respective baseline PSD to remove the power-law effect. At the group level for each group, percent changes of EEG powers per channel were statistically compared between (1) tPBM vs light-stimulation sham, (2) thermo_stim vs heat-stimulation sham, and (3) tPBM vs thermo_stim after sham exclusion at five frequency bands using the non-parametric permutation tests. By performing the false discovery rate correction for multi-channel comparisons, we showed by EEG power change topographies that (1) tPBM significantly increased EEG alpha and beta powers, (2) the thermal stimulation created opposite effects on EEG power topographic patterns, and (3) tPBM and thermal stimulations induced significantly different topographies of changes in EEG alpha and beta power. Overall, this study provided evidence to support our hypothesis, showing that the laser-induced heat on the human forehead is not a mechanistic source causing increases in EEG power during and after tPBM.

We tested the role of hypnotic suggestibility, involuntariness, pain expectation, and subjective hypnotic depth in the prediction of placebo analgesia (PA) responsiveness. We also tested the link of lower and upper alpha sub-band (i.e., 'alpha1' and 'alpha2') power changes with tonic PA responding during waking and hypnosis conditions. Following an initial PA manipulation condition, we recorded EEG activity during waking and hypnosis under two treatments: (1) painful stimulation (Pain); (2) painful stimulation after application of a PA cream. Alpha1 and alpha2 power were derived using the individual alpha frequency method. We found that (1) PA in both waking and hypnosis conditions significantly reduced relative pain perception; (2) during waking, all the above mentioned contextual measures were associated with pain reduction, while involuntariness alone was associated with pain reduction within hypnosis. Enhanced alpha2 power at the left-parietal lead was solely associated with pain reduction in waking, but not in hypnosis condition. Using multiple regression and mediation analyses we found that: (i) during waking, the enhancement of relative left-parietal alpha2 power, directly influenced the enhancement in pain reduction, and, indirectly, through the mediating positive effect of involuntariness; (j) during hypnosis, the enhancement of left-temporoparietal alpha2 power, through the mediation of involuntariness, influenced pain reduction. Current findings obtained during waking suggest that enhanced alpha2 power may serve as a direct-objective measure of the subjective reduction of tonic pain in response to PA treatment. Overall, our findings suggest that placebo analgesia during waking and hypnosis involves different processes of top-down regulation.

For decades, the frontal alpha asymmetry (FAA) – a disproportion in EEG alpha oscillations power between right and left frontal channels – has been one of the most popular measures of depressive disorders (DD) in electrophysiology studies. Patients with DD often manifest a left-sided FAA: relatively higher alpha power in the left versus right frontal lobe. Recently, however, multiple studies failed to confirm this effect, questioning its reproducibility. Our purpose is to thoroughly test the validity of FAA in depression by conducting a multiverse analysis – running many related analyses and testing the sensitivity of the effect to changes in the analytical approach – on data from five independent studies. Only 13 of the 270 analyses revealed significant results. We conclude the paper by discussing theoretical assumptions underlying the FAA and suggest a list of guidelines for improving and expanding the EEG data analysis in future FAA studies.

Recent evidence suggests that relative to nonshy children, shy children exhibit a lower overall frontal EEG alpha/delta ratio (ADR) during middle childhood, possibly reflecting relatively less frontal brain maturation at this age. We examined this same ADR measure in relation to the stability of observed shyness and parent-reported child social anxiety measured across two laboratory visits separated by approximately 1 year during late childhood in 51 children (33% female, age range 10-16 years). We found that the overall frontal ADR score was significantly lower among children with high, stable observed shyness and parent-reported child social anxiety compared to children in the low, stable class. Findings provide convergent evidence suggesting that the stability of shyness in late childhood may be linked to relatively less overall frontal brain maturation at this age. We speculate on the adaptive function of delaying frontal brain maturation in the origins and maintenance of children's shyness.

What is your brain doing while your mind is wandering? This study used a within-subjects experience-sampling design to test whether episodes of mind-wandering during a demanding cognitive task are associated with increases in EEG alpha power. Alpha refers to cyclic oscillations in EEG activity at 8-12 Hz, and has been previously correlated with internally rather than externally directed cognition. Participants completed a speeded performance task with more than 800 trials while EEG was recorded. Intermittent experience-sampling probes asked participants to indicate whether their mind was wandering or on-task. Participants reported mind-wandering in response to approximately half of the probes. EEG alpha power was significantly higher preceding probes to which participants reported mind-wandering, compared with probes to which participants reported being on task. These findings imply that dynamic changes in alpha power may prove a valuable tool in studying momentary fluctuations in mind-wandering.

Working memory contents can be prioritized by retroactively deploying attention within memory. This is broadly interpreted as evidence of a concentration of memory resources to the attended, to-be-remembered stimulus. However, online attentional selection is known to additionally depend on distractor inhibition, raising the viable alternative that attentional deployment in working memory involves inhibitory control processes. Here, we demonstrate that active inhibition plays a central role in the deployment of attention in working memory. We do so using a retroactive cueing paradigm, where a briefly presented memory array is followed by a cue indicating a to-be-remembered target (Experiment 1) or a to-be-forgotten distractor (Experiment 2). We identify discrete indices of target selection and distractor inhibition in lateralized oscillatory activity over visual areas. When a retroactive cue identifies the location of a target, results show rapid decrease of lateral, target-elicited alpha band activity, representing attentional orienting toward the target. This is followed only later by emergence of an increase in distractor-elicited alpha activity, reflecting distractor inhibition. In contrast, when the retroactive cue identifies a distractor, evidence of distractor inhibition emerges first, only later followed by target selection. These results thus demonstrate that separate excitatory and inhibitory processes underlie the deployment of attention on the level of working memory representations.

The allocation of mental workload is critical to maintain cognitive-motor performance under various demands. While mental workload has been investigated during performance, limited efforts have examined it during cognitive-motor learning, while none have concurrently manipulated task difficulty. It is reasonable to surmise that the difficulty level at which a skill is practiced would impact the rate of skill acquisition and also the rate at which mental workload is reduced during learning (relatively slowed for challenging compared to easier tasks). This study aimed to monitor mental workload by assessing cortical dynamics during a task practiced under two difficulty levels over four days while perceived task demand, performance, and electroencephalography (EEG) were collected. As expected, self-reported mental workload was reduced, greater working memory engagement via EEG theta synchrony was observed, and reduced cortical activation, as indexed by progressive EEG alpha synchrony was detected during practice. Task difficulty was positively related to the magnitude of alpha desynchrony and accompanied by elevations in the theta-alpha ratio. Counter to expectation, the absence of an interaction between task difficulty and practice days for both theta and alpha power indicates that the refinement of mental processes throughout learning occurred at a comparable rate for both levels of difficulty. Thus, the assessment of brain dynamics was sensitive to the rate of change of cognitive workload with practice, but not to the degree of difficulty. Future work should consider a broader range of task demands and additional measures of brain processes to further assess this phenomenon.

EEG resting state alpha asymmetry is one of the most widely investigated forms of functional hemispheric asymmetries in both basic and clinical neuroscience. However, studies yield very inconsistent results. One crucial prerequisite to obtain reproducible results is the reliability of the index of interest. There is a body of research suggesting a moderate to good reliability of EEG resting state alpha asymmetry, but unfortunately sample sizes in these studies are typically small. This study presents the first large scale short-term reliability study of frontal and parietal EEG resting state alpha asymmetry. We used the Dortmund Vital Study data set containing 541 participants. In each participant, EEG resting state was recorded eight times, twice with their eyes opened, twice with their eyes closed, each on two different EEG systems. We found good reliability of EEG alpha power and alpha asymmetry on both systems. Interestingly, we found no reliable alpha asymmetry in frontomedial brain regions, one of the most investigate brain regions in alpha asymmetry research. Furthermore, we investigated the link between EEG alpha asymmetry and handedness, since previous studies showed that right-handedness is associated with higher rightward alpha asymmetry. Our results only partly replicate this association. In conclusion, our results suggest that while EEG alpha asymmetry is an overall reliable measure, frontal alpha asymmetry should be assessed by using multiple electrode pairs. Furthermore, the question of EEG alpha asymmetry’s association with handedness remains unsettled and needs further investigation.

Although there is consistent evidence that exposure to radiofrequency electromagnetic fields (RF-EMF) increases the spontaneous resting alpha spectral power of the electroencephalogram (EEG), the reliability of this evidence is uncertain as some studies have also failed to observe this effect. The present study aimed to determine whether the effect of RF-EMF exposure on EEG alpha power depends on whether EEG is derived from eyes open or closed conditions and assessed earlier (5-min) versus later (25-min) in the exposure interval. Thirty-six adults participated in three experimental sessions, each involving one exposure: "Sham," "Low," and "High" RF-EMF corresponding to peak spatial specific absorption rates averaged over 10 g of 0, 1, and 2 W/kg, respectively. Resting EEG was recorded at baseline (no exposure), during, and after exposure. Alpha power increase was found to be greater for the eyes open than eyes closed EEG during both the High (P = 0.04) and Low (P = 0.04) RF-EMF exposures. There was also a trend toward it being larger at the end, versus the start of the "High" 30-min exposure (P 0.01; eyes open condition). This suggests that the use of eyes closed conditions, and insufficient RF-EMF exposure durations, are likely explanations for the failure of some studies to detect an RF-EMF exposure-related increase in alpha power, as such methodological choices decrease signal-to-noise ratios and increase type II error.

Transcranial Direct Current Stimulation (tDCS) has been used as an alternative treatment for pain reduction in fibromyalgia. In this study, in addition to behavioral measures, we analyzed oscillations in alpha 2 frequency band in the frontal, occipital, and parietal regions, in response to the application of two neuromodulation protocols in fibromyalgia. The study was a randomized, double-blind, placebo-controlled clinical trial with 31 women diagnosed with fibromyalgia. The participants were allocated to three groups with the anodic stimulation applied on the left motor cortex: Group 1, for five consecutive days; Group 2, for 10 consecutive days; and Group 3, sham stimulation for five consecutive days. Statistical analysis showed a reduction in pain intensity after treatment for groups in general [F (1.28) = 8.02; p = 0.008; η2 = 0.223], in addition to a reduction in alpha 2 in the frontal (p = 0.039; d = 0.384) and parietal (p = 0.021; d = 0.520) regions after the treatment on five consecutive days. We conclude that neuromodulation protocols produced similar effects on pain reduction, but differed with respect to the changes in the alpha 2 frequency band in the frontal and parietal regions.

Resting frontal EEG alpha asymmetry has been extensively examined as a marker of motivational disposition. Recent research has examined how this trait-level marker of motivation influences an individual’s internal error monitoring (indexed by the error-related negativity; ERN), with mixed findings as to whether more negative ERNs are associated with greater left or right alpha power. Data from 339 children who completed an incentivized Go/No-Go task annually from Kindergarten through 2nd grade were examined for an association between ERN amplitude and EEG asymmetry, and for whether the association was developmentally stable. Results indicate an association between left-dominant activation and a more negative amplitude in Kindergarten, with an inversion of this association emerging by 2nd grade, such that a more negative ERNs were associated with right-dominant activation. We suggest that the association between EEG asymmetry and ERN amplitude is likely modulated by task condition (e.g., incentivization) and experience over time (e.g., habituation).

Objective This study aims to understand the neural and hemodynamic responses during general anesthesia in order to develop a comprehensive multimodal anesthesia depth monitor using simultaneous functional Near Infrared Spectroscopy (fNIRS) and Electroencephalogram (EEG). Methods 37 adults and 17 children were monitored with simultaneous fNIRS and EEG, during the complete general anesthesia process. The coupling of fNIRS signals with neuronal signals (EEG) was calculated. Measures of complexity (sample entropy) and phase difference were also quantified from fNIRS signals to identify unique fNIRS based biomarkers of general anesthesia. Results A significant decrease in the complexity and power of fNIRS signals characterize the anesthesia maintenance phase. Furthermore, responses to anesthesia vary between adults and children in terms of neurovascular coupling and frontal EEG alpha power. Conclusions This study shows that fNIRS signals could reliably quantify the underlying neuronal activity under general anesthesia and clearly distinguish the different phases throughout the procedure in adults and children (with less accuracy). Significance A multimodal approach incorporating the specific differences between age groups, provides a reliable measure of anesthesia depth.

Motivationally/emotionally engaging stimuli are strong competitors for the limited capacity of sensory and cognitive systems. Thus, they often act as distractors, interfering with performance in concurrent primary tasks. Keeping task-relevant information in focus while suppressing the impact of distracting stimuli is one of the functions of working memory (WM). Macroscopic brain oscillations in the alpha band (8-13 Hz) have recently been identified as a neural correlate of WM processing. Using electroencephalography, we examined the extent to which changes in alpha power and inter-site connectivity during a typical WM task are sensitive to load and emotional distraction. Participants performed a lateralized change-detection task with two levels of load (four vs. two items), which was preceded by naturalistic scenes rated either as unpleasant or neutral, acting as distractors. The results showed the expected parieto-occipital alpha reduction in the hemisphere contralateral to the WM task array, compared to the ipsilateral hemisphere, during the retention interval. Selectively heightened oscillatory coupling between frontal and occipital sensors was observed (1) during the retention interval as a function of load, and (2) upon the onset of the memory array, after viewing neutral compared to unpleasant distractors. At the end of the retention interval, we observed greater coupling during the unpleasant compared to the neutral condition. These findings are consistent with the notions that (1) representing more items in WM requires greater interconnectivity across cortical areas, and (2) unpleasant emotional distractors interfere with subsequent WM processing by disrupting processing during the encoding stage.

Prior research has shown that greater EEG alpha power (8–13 ​Hz) is characteristic of more creative individuals, and more creative task conditions. The present study investigated the potential for machine learning to classify more and less creative brain states. Participants completed an Alternate Uses Task, in which they thought of Normal or Uncommon (more creative) uses for everyday objects (e.g., brick). We hypothesized that alpha power would be greater for Uncommon (vs. Common) uses, and that a machine learning (ML) approach would enable the reliable classification data from the two conditions. Further, we expected that ML would be successful at classifying more (vs. less) creative individuals. As expected, alpha power was significantly greater for the Uncommon than for the Normal condition. Using spectrally weighted common spatial patterns to extract EEG features, and quadratic discriminant analysis, we found that classification accuracy for the two conditions varied widely among individuals, with a mean of 63.9%. For more vs. less creative individuals, 82.3% classification accuracy was attained. These findings indicate the potential for broader adoption of machine learning in creativity research.

© 2020 Elsevier B.V. This study tested the validity of EEG left-temporal alpha power and upper-alpha T7-Fz connectivity as indices of verbal activity and conscious motor control. Participants (n = 20) reached for, and transported, a jar under three conditions: a control condition and two self-talk conditions aimed at eliciting either task-unrelated verbal processing or task-related conscious control, while EEG and hand kinematics were recorded. Compared to the control condition, both self-talk conditions increased self-reported verbal processing, but only the task-related self-talk condition increased left-temporal activity (i.e., alpha power decreased). However, as cortical activity increased across the entire scalp topography, conscious control likely elicits a multitude of processes that may not be explained by left-temporal activity or verbal processing alone, but by a widespread decrease in neural efficiency. No significant effects for T7-Fz connectivity were detected. Results suggest that left-temporal EEG alpha oscillations are unlikely to uniquely reflect verbal processing during conscious motor control.

Cognitive reappraisal is an important emotion regulation skill for psychological health and well-being, however, some people cannot use this strategy effectively. We investigated EEG alpha asymmetry by calculating lateral index (LI) when twenty-six healthy participants were instructed to complete the emotion cognitive reappraisal task of viewing neutral pictures, watching negative pictures and reappraising negative pictures. According to self-reported valence and arousal, the participants were divided into effective and ineffective groups. Habitual use of rumination was also assessed using the Cognitive Emotion Regulation Questionnaire (CERQ). EEG alpha asymmetry results demonstrated that, ineffective group showed greater relative right temporal activity than effective group in the early stage of reappraisal, indicating higher subjective arousal. Both groups showed greater relative left frontal alpha activity in the late stages of reappraisal compared with watching negative images, indicating the recruitment of corresponding functions in prefrontal regulatory circuitry during the effort of reappraisal. CERQ analysis results showed that, ineffective group got significantly higher score than effective group in habitual use of rumination. Partial correlation revealed that, in male participants, temporal LI change (negative-reappraisal minus negative-watch) was negatively correlated with self-reported arousal and habitual use of rumination. In addition, by using K-means cluster analysis, temporal LI combined with CERQ-rumination score achieved a classification accuracy of 84.6 %. These findings suggested that, EEG alpha asymmetry as well as the habitual use of rumination accounted for the reappraisal effectiveness.

Objective The aim of this study is to evaluate the effectiveness of a seat-integrated mobilization system for maintaining vigilance under monotonous driving situations. Method For this purpose, vigilance indicators were compared intra-individually in a test condition with mobilization (seat-integrated stimulation) and a placebo condition under standardized conditions in a real driving study (N = 31). During a monotonous two-hour ride, physiological (brain activity by the EEG alpha spindle rate), performance-based (reaction times) and subjective indicators were recorded. Results The necessary precondition for the paradigm of inducing fatigue through monotony was confirmed by a significant increase in the EEG alpha spindle rate and the subjective vigilance indices. The mobilization system had a significant impact on the most fatigue-sensitive parameter of the alpha spindle rate, whereas the other parameters of vigilance did not reflect a significant effect of mobilization. Conclusion The Mobilization Seat is an effective measure to prevent drivers’ fatigue during monotonous situations.

Summary To behave adaptively with sufficient flexibility, biological organisms must cognize beyond immediate reaction to a physically present stimulus. For this, humans use visual mental imagery [1, 2], the ability to conjure up a vivid internal experience from memory that stands in for the percept of the stimulus. Visually imagined contents subjectively mimic perceived contents, suggesting that imagery and perception share common neural mechanisms. Using multivariate pattern analysis on human electroencephalography (EEG) data, we compared the oscillatory time courses of mental imagery and perception of objects. We found that representations shared between imagery and perception emerged specifically in the alpha frequency band. These representations were present in posterior, but not anterior, electrodes, suggesting an origin in parieto-occipital cortex. Comparison of the shared representations to computational models using representational similarity analysis revealed a relationship to later layers of deep neural networks trained on object representations, but not auditory or semantic models, suggesting representations of complex visual features as the basis of commonality. Together, our results identify and characterize alpha oscillations as a cortical signature of representations shared between visual mental imagery and perception., Highlights • Perception and imagery share neural representations in the alpha frequency band • Shared representations stem from parieto-occipital sources • Modeling suggests contents of shared representations are complex visual features, Visual imagination is a key cognitive function with the feel of weak visual perception. Xie et al. show that this phenomenal likeness is mirrored by neural likeness in shared representations of complex visual features in the alpha frequency band activity arising from parieto-occipital cortex.

The evolution of virtual reality (VR) technologies requires setting boundaries of its use. In this study, 3 female participants were experiencing VR scenarios with stressful content and their activity of the autonomic nervous system and EEG were recorded. It has been discovered that virtual reality can evoke acute stress reactions accompanied by activation of the sympathetic nervous system and a decrease in the activity of the parasympathetic nervous system. The high-stress response is accompanied by a decrease in the power of the EEG, and, on the contrary, the activation of the avoidance reaction is accompanied by an increase in the power of the EEG alpha waves. Therefore, the use of stressful VR content can cause high emotional stress to a user and restrictions should be considered.

In recent years, the influence of alpha (7–13 Hz) phase on visual processing has received a lot of attention. Magneto‐/encephalography (M/EEG) studies showed that alpha phase indexes visual excitability and task performance. Studies with transcranial alternating current stimulation (tACS) aim to modulate oscillations and causally impact task performance. Here, we applied right occipital tACS (O2 location) to assess the functional role of alpha phase in a series of experiments. We presented visual stimuli at different pre‐determined, experimentally controlled, phases of the entraining tACS signal, hypothesizing that this should result in an oscillatory pattern of visual performance in specifically left hemifield detection tasks. In experiment 1, we applied 10 Hz tACS and used separate psychophysical staircases for six equidistant tACS‐phase conditions, obtaining contrast thresholds for detection of visual gratings in left or right hemifield. In experiments 2 and 3, tACS was at EEG‐based individual peak alpha frequency. In experiment 2, we measured detection rates for gratings with (pseudo‐)fixed contrast. In experiment 3, participants detected brief luminance changes in a custom‐built LED device, at eight equidistant alpha phases. In none of the experiments did the primary outcome measure over phase conditions consistently reflect a one‐cycle sinusoid. However, post hoc analyses of reaction times (RT) suggested that tACS alpha phase did modulate RT for specifically left hemifield targets in both experiments 1 and 2 (not measured in experiment 3). This observation requires future confirmation, but is in line with the idea that alpha phase causally gates visual inputs through cortical excitability modulation., In a series of experiments, visual stimuli were presented at pre‐determined phases of an alpha‐frequency tACS signal applied to right occipital cortex. Curve‐fitting analyses revealed no effects on visual detection or thresholds, but possible post hoc effects on reaction times in left visual field.

Visual working memory (VWM) distinguishes between representations relevant for imminent versus future perceptual goals. We investigated how the brain sequentially prioritizes visual working memory representations that serve consecutive tasks. Observers remembered two targets for a sequence of two visual search tasks, thus making one target currently relevant, and the other prospectively relevant. We show that during the retention interval prior to the first search, lateralized parieto-occipital EEG alpha (8–14 Hz) suppression is stronger for current compared with prospective search targets. Crucially, between the first and second search task, this difference in posterior alpha lateralization reverses, reflecting the change in priority states of the two target representations. Connectivity analyses indicate that this switch in posterior alpha lateralization is driven by frontal delta/low-theta (2–6 Hz) activity. Moreover, this frontal low-frequency signal also predicts task performance after the switch. We thus obtained evidence for large-scale network interactions underlying the flexible shifting between the priority states of multiple memory representations in VWM.

Acute physical exercise (APE) induces an increase in the individual alpha peak frequency (iAPF), a cortical parameter associated with neural information processing speed. The aim of this study was to further scrutinize the influence of different APE intensities on post-exercise iAPF as well as its time course after exercise cessation. 95 healthy young (18-35 years) subjects participated in two randomized controlled experiments (EX1 and EX2). In EX1, all participants completed a graded exercise test (GXT) until exhaustion and were randomly allocated into different delay groups (immediately 0, 30, 60 and 90 min after GXT). The iAPF was determined before, immediately after as well as after the group-specific delay following the GXT. In EX2, participants exercised for 35 min at either 45-50%, 65-70% or 85-90% of their maximum heart rate (HRmax). The iAPF was determined before, immediately after as well as 20 min after exercise cessation. In EX1, the iAPF was significantly increased immediately after the GXT in all groups. This effect was not any more detectable after 30 min following exercise cessation. In EX2, a significant increase of the iAPF was found only after high-intensity (85-90% HRmax) exercise. The results indicate intense or exhaustive physical exercise is required to induce a transient increase in the iAPF that persists about 30 min following exercise cessation. Based on these findings, further research will have to scrutinize the behavioral implications associated with iAPF modulations following exercise.

In the majority of studies investigating cortical alpha oscillations the alpha frequency is defined as a fixed band thus, neglecting recommendations in the EEG literature to adjust the alpha band according to the individual alpha peak frequency (iAPF). Based on our previous findings indicating exhaustive exercise induces an increase of the post-exercise iAPF, we scrutinized the influence of exercise on post-exercise alpha power by comparing fixed and iAPF-adjusted alpha frequency bands. Resting EEG was recorded from 13 scalp locations in nine subjects before, immediately after as well as ten minutes following an exhaustive exercise protocol on a cycle ergometer. Lower and upper band alpha power was calculated for fixed and iAPF-adjusted frequency bands. Post-exercise lower alpha power increased in both fixed and individually defined bands while a higher upper alpha power was only observed in the fixed frequency band condition. Further, the increase in iAPF was positively related to the changes in fixed-band upper alpha power. It is concluded that lower alpha power is significantly increased following exhaustive exercise whereas the results for upper alpha power are substantially influenced by the method of frequency band definition. Therefore, caution is indicated when analyzing and interpreting exercise-induced changes in alpha power.

Do physiological and behavioral performance indicators of effortful cognitive self-regulation converge additively or interactively in their statistical prediction of individual differences in harsh parenting? To answer this question, we examined heart rate (HR) and electroencephalography alpha (α) reactivity during executive function (EF) tasks, along with observed and self-reported indicators of harsh parenting. A socioeconomically diverse sample of 115 mothers with 3- to 7-year-old children completed questionnaires and a laboratory visit. Three quarters of the mothers showed typical patterns of task reactivity that were interpretable (i.e., increases in HR and decreases in α). Among them, we found no evidence to suggest that variance in harsh parenting was associated with magnitude of HR or α reactivity independently. Instead, the physiological variables interacted to enhance the EF statistical effect. EF explained one third of the variance in harsh parenting among mothers showing the largest α decreases when accompanied by modest to moderate (rather than substantial) HR increases. Physiological indicators can clarify the role and estimation of the strength of the effect of direct behavioral measures of cognitive regulation in the etiology of harsh parenting behaviors. (PsycINFO Database Record

Frontal electroencephalographic (EEG) alpha asymmetry is widely researched in studies of emotion, motivation, and psychopathology, yet it is a metric that has been quantified and analyzed using diverse procedures, and diversity in procedures muddles cross-study interpretation. The aim of this article is to provide an updated tutorial for EEG alpha asymmetry recording, processing, analysis, and interpretation, with an eye towards improving consistency of results across studies. First, a brief background in alpha asymmetry findings is provided. Then, some guidelines for recording, processing, and analyzing alpha asymmetry are presented with an emphasis on the creation of asymmetry scores, referencing choices, and artifact removal. Processing steps are explained in detail, and references to MATLAB-based toolboxes that are helpful for creating and investigating alpha asymmetry are noted. Then, conceptual challenges and interpretative issues are reviewed, including a discussion of alpha asymmetry as a mediator/moderator of emotion and psychopathology. Finally, the effects of two automated component-based artifact correction algorithms—MARA and ADJUST—on frontal alpha asymmetry are evaluated.

Adolescent idiopathic scoliosis (AIS) is a multifactorial disorder characterized by a tridimensional deformation of the spine. AIS pathophysiology is still unclear and its aetiology is unknown. Results from several studies revealed balance control alterations in adolescents with AIS suggesting cortical sensorimotor processing impairments. Studies assessing cortical activity involved in balance control revealed an increase in alpha peak frequency (APF), which is a neurophysiological marker of thalamo-cortical transmission, related to a more challenging balance task. The objective of this study is to assess APF of adolescents with AIS during balance control in upright standing posture using electroencephalography (EEG). EEG was recorded in 16 girls with AIS and 15 control girls in normal standing posture on a force platform. The participants stood upright for 2 min with eyes open and 2 min with eyes closed. Fast Fourier transformations of EEG data were calculated to obtain APF. Balance performances were assessed through the area of an ellipse covering the center of pressure (COP) displacement and the root mean square value of the COP velocity. Compared to the control group, APF was higher in the AIS group at central, frontal, parietal and occipital regions. Further, COP analyses did not reveal any difference between AIS and control groups. A higher APF may indicate the need for increased cortical processing to maintain balance control in normal upright standing in adolescents with AIS compared to healthy controls. We suggest that this may be a compensatory strategy to overcome balance control challenges.

Oscillatory neural activity is a fundamental characteristic of the mammalian brain spanning multiple levels of spatial and temporal scale. Current theories of neural oscillations and analysis techniques employed to investigate their functional significance are based on an often implicit assumption: In the absence of experimental manipulation, the spectral content of any given EEG- or MEG-recorded neural oscillator remains approximately stationary over the course of a typical experimental session (~1 hour), spontaneously fluctuating only around its dominant frequency. Here, we examined this assumption for ongoing neural oscillations in the alpha-band (8:13 Hz). We found that alpha peak frequency systematically decreased over time, while alpha-power increased. Intriguingly, these systematic changes showed partial independence of each other: Statistical source separation (independent component analysis) revealed that while some alpha components displayed concomitant power increases and peak frequency decreases, other components showed either unique power increases or frequency decreases. Interestingly, we also found these components to differ in frequency. Components that showed mixed frequency/power changes oscillated primarily in the lower alpha-band (~8-10Hz), while components with unique changes oscillated primarily in the higher alpha-band (~9-13Hz). Our findings provide novel clues on the time-varying intrinsic properties of large-scale neural networks as measured by M/EEG, with implications for the analysis and interpretation of studies that aim at identifying functionally relevant oscillatory networks or at driving them through external stimulation.

Apathy is a common non-motor symptom of Parkinson's disease (PD) that is difficult to quantify and poorly understood. Some studies have used incentivized motor tasks to assess apathy, as the condition is often associated with a reduction in motivated behavior. Normally event-related desynchronization, a reduction of power in specific frequency bands, is observed in the motor cortex during the peri-movement period. Also, alpha (8–12 Hz) and theta (4–7 Hz) oscillations are sensitive to rewards that are closely related to motivational states however these oscillations have not been widely investigated in relation to apathy in PD. Using EEG recordings, we investigated the neural oscillatory characteristics of apathy in PD during an incentivized motor task with interleaved rest periods. Apathetic and non-apathetic PD subjects on dopaminergic medication and healthy control subjects were instructed to squeeze a hand grip device for a monetary reward proportional to the subject's grip force and the monetary value attributed to that trial. Apathetic PD subjects exhibited higher alpha and theta powers in the pre-trial baseline rest period compared to non-apathetic PD subjects and healthy subjects. Further, we found that both resting power and relative power in alpha and theta bands during incentivized movement predicted PD subjects' apathy scores. Our results suggest that apathetic PD patients may need to overcome greater baseline alpha and theta oscillatory activity in order to facilitate incentivized movement. Clinically, resting alpha and theta power as well as alpha and theta event-related desynchronization during movement may serve as potential neural markers for apathy severity in PD., Highlights • Apathetic patients with Parkinson's disease on dopaminergic medication have distinct neural oscillatory characteristics. • Apathetic patients exhibit a higher resting EEG theta and alpha power compared to non-apathetic patients. • Both resting power and relative event-related theta and alpha desynchronization during squeezing are able to predict patient apathy scores.

There are ample inter-individual differences in the frequency with which people perceive meaningful coincidences. Previous research has identified increased proactive interference, that is a reduced working memory capacity, as one possible mechanism associated with this phenomenon. The present study aimed at extending this finding into the domain of neuroscience, (1) by assessing EEG alpha oscillations during the retention of information, (2) by replicating the behavioral link between meaningful coincidences and proactive interference. In a sample of 52 participants, the behavioral replication was successful. Furthermore, participants who perceived more meaningful coincidences showed higher alpha power increases at parietal-occipital sites, and at the same time, displayed lower alpha power increases at frontal areas, during retention of information. This neurophysiological activation pattern further underlines the assumption that participants who perceive more meaningful coincidences show lower working memory capacities, since increased alpha power at parietal areas reflects a higher load on working memory demands.

The objective of this study was to compare the development of sleepiness during manual driving versus level 2 partially automated driving, when driving on a motorway in Sweden. The hypothesis was that partially auto-mated driving will lead to higher levels of fatigue due to underload. Eighty-nine drivers were included in the study using a 2 ? 2 design with the conditions manual versus partially automated driving and daytime (full sleep) versus night-time (sleep deprived). The results showed that night-time driving led to markedly increased levels of sleepiness in terms of subjective sleepiness ratings, blink durations, PERCLOS, pupil diameter and heart rate. Partially automated driving led to slightly higher subjective sleepiness ratings, longer blink durations, decreased pupil diameter, slower heart rate, and higher EEG alpha and theta activity. However, elevated levels of sleepiness mainly arose from the night-time drives when the sleep pressure was high. During daytime, when the drivers were alert, partially automated driving had little or no detrimental effects on driver fatigue. Whether the negative effects of increased sleepiness during partially automated driving can be compensated by the positive effects of lateral and longitudinal driving support needs to be investigated in further studies. Funding Agencies|ADASME [688900]; Mediator projects - European Unions Horizon 2020 research and innovation programme [814735]; Autoliv Development; SmartEye AB

Background EEG mu rhythm suppression is assessed in experiments on the execution, observation and imagination of movements. It is utilised for studying of actions, language, empathy in healthy individuals and preservation of sensorimotor system functions in patients with schizophrenia and autism spectrum disorders. While EEG alpha and mu rhythms are recorded in the same frequency range (8−13 Hz), their specification becomes a serious issue. The new method is based on the spatial and functional characteristics of the mu wave, which are: (1) the mu rhythm is located over the sensorimotor cortex; (2) it desynchronises during movement processing and does not respond on the eyes opening. In EEG recordings, we analysed the mu rhythm under conditions with eyes opened and eyes closed (baseline), and during a motor imagery task with eyes closed. EEG recordings were processed by principal component analysis (PCA). Results The analysis of EEG data with the proposed approach revealed the maximum spectral power of mu rhythm localised in the sensorimotor areas. During motor imagery, mu rhythm was suppressed more in frontal and central sites than in occipital sites, whereas alpha rhythm was suppressed more in parietal and occipital sites. Mu rhythm desynchronization in sensorimotor sites during motor imagery was greater than alpha rhythm desynchronization. The proposed method enabled EEG mu rhythm separation from its mix with alpha rhythm. Conclusions EEG mu rhythm separation with the proposed method satisfies its classical definition.

Objective The present study examined whether neural indices of working memory maintenance differ between young adults with ADHD and their healthy peers (Study 1), and whether this neural index would change after working memory training (Study 2). Methods Study 1 involved 136 college students with ADHD and 41 healthy peers (aged 18–35 years) and measured their posterior alpha activity during a visual delayed-match-to-sample task using electroencephalography (EEG). Study 2 involved 99 of the participants with ADHD who were randomized into a standard-length or shortened-length Cogmed working memory training program or a waitlist control group. Results The ADHD group tended to be less accurate than the peers. Similarly, the ADHD group exhibited lower posterior alpha power at a trend level compared to their healthy peers. There were no training effects on participants’ performance and only marginal increases in posterior alpha power in training groups compared to the waitlist group. Conclusions Considering that the training effects were small and there was no load and dose effect, we conclude that the current study provides no convincing evidence for specific effects of Cogmed. Significance These findings provide unique insights into neuroplasticity, or lack thereof, with near-transfer tasks in individuals with ADHD.

We use a unique environment of Whole Body Perceptual Deprivation (WBPD) to induce an altered state of consciousness (ASC) in our participants, and employ online EEG recording. We present individual EEG alpha profiles, and show how these data can be analyzed at the individual level. Our goal is to investigate to what degree subjective experience matches EEG alpha profile, and in particular, the various alpha hemispheric asymmetries observed in the frontal, parietal, and occipital lobes. Specifically, we consider positive (frontal LR) or negative (frontal LR) affect; a more verbal (LR) or a more imagistic (RL) mode of thinking; and a more trancelike (frontalparietal) or more reflective (frontalparietal) state of consciousness. Our results indicate that the individual alpha profiles are reflected in individual differences in subjective experience. However, the alpha profiles are confounded with the gender of the participant. Specifically, there is a predominant RL asymmetry found for male participants, and a predominant LR asymmetry found for female participants.

In a community-based sample of 104 infants and their mothers, we hypothesized a pathway from postnatal maternal symptoms of depression to child emotion dysregulation, and tested at 6 months of age the mediation role of alpha asymmetry at frontal and parietal sites. We recorded infant resting-state EEG at 6 months of age. Child emotion dysregulation was measured at 24 months by the Child Behavior Checklist Dysregulation Profile derived from the CBCL 1½-5. Maternal depression symptoms were scored 6 months after the delivery by the Anxious/Depressed scale of the Adult Self-Report. We used structural equation modeling to test the mediation model from maternal depression symptoms to child emotion dysregulation mediated by frontal and parietal alpha asymmetry. The mediation model provided an excellent fit to the data [χ2(3) = 3.088, p = .378; RMSEA = .017, CFI = .1.00; SRMR = 0.040] and explained 23.3% of the variance in child emotion dysregulation. The indirect path via parietal alpha asymmetry was significant (β = .065; SE = .033; 95% CI = .001–.139; p = .048), i.e. greater levels of maternal depression symptoms predicted left parietal alpha asymmetry, which predicted higher levels of child emotion dysregulation. The direct effect, i.e. the pathway linking maternal depression symptoms and child emotion dysregulation above and beyond the indirect effects, was also significant. We found evidence for a partial mediation role of left parietal alpha asymmetry in a longitudinal pathway from postnatal maternal symptoms of depression to child emotion dysregulation, providing support for left parietal asymmetry as an index of biological vulnerability to emotion dysregulation in the first years of life.

Affective dispositions may shape students' typical ways of coping when faced with demanding performance situations in their educational lives. We recorded frontal EEG alpha asymmetry responses in psychology students (n = 62) during the course of a scenario designed to simulate a real examination, which required oral explanation of statistical concepts. While students with lower levels of trait positive affect (PANAS) showed relative right hemispheric activation, sustained relative left hemispheric activation was observed in students with higher levels of trait positive affect. In line with relevant models of frontal brain asymmetry, the findings suggest that students' coping behaviors in the context of academic performance situations are in part instantaneously initiated, which is reflected in spontaneous activation of relative approach versus avoidance motivation. Independently of negative affect and momentary affective states, trait positive affectivity seems to be linked to recruitment of brain processes supporting a more adaptive response in that matter.

Objective Greater relative right- than left-frontal cortical activity has been frequently found in adults with major depression (MD). As the few studies in adolescents with MD have been inconclusive, the aim of this study was to assess frontal alpha asymmetry (FAA) in an adolescent sample with MD whilst taking into account possible confounding variables such as disease state and comorbid anxiety disorder. Methods An 8-minute resting frontal EEG was assessed in 34 healthy controls (HCs), 16 adolescents with MD in remission without comorbid anxiety disorder (rMDa−), 22 adolescents with acute depression without comorbid anxiety disorder (MDa−), and 23 adolescents with acute depression and comorbid anxiety disorder (MDa+). Alpha power was analyzed over corresponding frontal Regions of Interests. Results Compared to HCs, MDa+ adolescents demonstrated more left- than right-sided EEG alpha power, indicating greater right-than left-frontal cortical activity. No other group differences emerged. Conclusions The results suggest that greater relative right-frontal cortical activity in adolescent MD is not a result of disease state but can be attributed to comorbid anxiety disorder. Significance Results suggest that FAA is not linked to adolescent depression per se and highlight the importance of considering comorbid disorders when examining asymmetry patterns in adolescent MD.

Nonlinear analysis of EEG recordings allows detection of characteristics that would probably be neglected by linear methods. This study aimed to determine a suitable epoch length for nonlinear analysis of EEG data based on its recurrence rate in EEG alpha activity (electrodes Fz, Oz, and Pz) from 28 healthy and 64 major depressive disorder subjects. Two nonlinear metrics, Lempel-Ziv complexity and scaling index, were applied in sliding windows of 20 seconds shifted every 1 second and in nonoverlapping windows of 1 minute. In addition, linear spectral analysis was carried out for comparison with the nonlinear results. The analysis with sliding windows showed that the cortical dynamics underlying alpha activity had a recurrence period of around 40 seconds in both groups. In the analysis with nonoverlapping windows, long-term nonstationarities entailed changes over time in the nonlinear dynamics that became significantly different between epochs across time, which was not detected with the linear spectral analysis. Findings suggest that epoch lengths shorter than 40 seconds neglect information in EEG nonlinear studies. In turn, linear analysis did not detect characteristics from long-term nonstationarities in EEG alpha waves of control subjects and patients with major depressive disorder patients. We recommend that application of nonlinear metrics in EEG time series, particularly of alpha activity, should be carried out with epochs around 60 seconds. In addition, this study aimed to demonstrate that long-term nonlinearities are inherent to the cortical brain dynamics regardless of the presence or absence of a mental disorder.

An experimentally tested neural field theory of the corticothalamic system is used to model brain activity and resulting experimental EEG data, and to elucidate the neural mechanisms and physiological basis of alpha-BOLD anticorrelation observed in concurrent EEG and fMRI measurements. Several studies have proposed that the anticorrelation originates from a causal link between changes in the alpha power and BOLD signal. However, the results in this study reveal that fluctuations in alpha and BOLD power do not generate one another but instead respectively result from high- and low-frequency components of the same underlying cortical activity, and that they are inversely correlated via variations in the strengths of corticothalamic and intrathalamic feedback, thereby explaining their anticorrelation.

Objective We previously identified posterior EEG alpha as a potential biomarker for antidepressant treatment response. To meet the definition of a trait biomarker or endophenotype, it should be independent of the course of depression. Accordingly, this report evaluated the temporal stability of posterior EEG alpha at rest. Methods Resting EEG was recorded from 70 participants (29 male; 46 adults), during testing sessions separated by 12 ± 1.1 years. EEG alpha was identified, separated and quantified using reference-free methods that combine current source density (CSD) with principal components analysis (PCA). Measures of overall (eyes closed-plus-open) and net (eyes closed-minus-open) posterior alpha amplitude and asymmetry were compared across testing sessions. Results Overall alpha was stable for the full sample (Spearman-Brown [ r SB ] = .834, Pearson's r = .718), and showed excellent reliability for adults ( r SB = .918; r = 0.848). Net alpha showed acceptable reliability for adults ( r SB = .750; r = .600). Hemispheric asymmetries (right-minus-left hemisphere) of posterior overall alpha showed significant correlations, but revealed acceptable reliability only for adults ( r SB = .728; r = .573). Findings were highly comparable between 29 male and 41 female participants. Conclusions Overall posterior EEG alpha amplitude is reliable over long time intervals in adults. Significance The temporal stability of posterior EEG alpha oscillations at rest over long time intervals is indicative of an individual trait.

Resting and task-related EEG alpha are used in studies of cognition and psychopathology. Although Laplacian methods have been applied, apprehensions about loss of global activity dissuade researchers from greater use except as a supplement to reference-dependent measures. The unfortunate result has been continued reliance on reference strategies that differ across labs, and a systemic preference for a montage-dependent average reference over true reference-free measures. We addressed these concerns by comparing resting- and task-related EEG alpha using three EEG transformations: nose- (NR) and average-referenced (AR) EEG, and the corresponding CSD. Amplitude spectra of resting and prestimulus task-related EEG (novelty oddball) and event-related spectral perturbations were scaled to equate each transformation. Alpha measures quantified for 8–12 Hz bands were: 1) net amplitude (eyes-closed minus eyes-open) and 2) overall amplitude (eyes-closed plus eyes-open); 3) task amplitude (prestimulus baseline) and 4) task event-related desynchronization (ERD). Mean topographies unambiguously represented posterior alpha for overall, net and task, as well as poststimulus alpha ERD. Topographies were similar for the three transformations, but differed in dispersion, CSD being sharpest and NR most broadly distributed. Transformations also differed in scale, AR showing less attenuation or spurious secondary maxima at anterior sites, consistent with simulations of distributed posterior generators. Posterior task alpha and alpha ERD were positively correlated with overall alpha, but not with net alpha. CSD topographies consistently and appropriately represented posterior EEG alpha for all measures.

Previous studies on insight problem solving using Chinese logogriphs as insight problems only investigated the time- and phase-locked changes of electrocortical responses triggered by Chinese logogriphs, but did not focus on what kind of brain state facilitates individuals to solve insight problems. To investigate this, we focused on participants' alpha activities (8-12 Hz) that closely correlates with insight problem solving and defocused attention while they were solving Chinese logogriphs. Results indicated that in the time window of 800-1400 ms after the presentation of target logogriphs, alpha power over parieto-central electrodes decreased relative to the reference interval in both the successful and unsuccessful logogriphs solving conditions. However, alpha power increased at parieto-occipital electrode sites in successful conditions compared with that in unsuccessful condition. The decrease in alpha activity in both conditions may reflect the cognitive demands in solving the target logogriphs. Furthermore, difference in alpha power between the successful and unsuccessful conditions at parieto-occipital electrode sites is associated with the process of heuristic information. Alpha synchronization observed in the successful condition compared to the unsuccessful condition might reflect a state of defocused attention that facilitates insight problem solving.

The beneficial effects of placebo treatments on fear and anxiety (placebo anxiolysis) are well known from clinical practice, and there is strong evidence indicating a contribution of treatment expectations to the efficacy of anxiolytic drugs. Although clinically highly relevant, the neural mechanisms underlying placebo anxiolysis are poorly understood. In two studies in humans, we tested whether the administration of an inactive treatment along with verbal suggestions of anxiolysis can attenuate experimentally induced states of phasic fear and/or sustained anxiety. Phasic fear is the response to a well defined threat and includes attentional focusing on the source of threat and concomitant phasic increases of autonomic arousal, whereas in sustained states of anxiety potential and unclear danger requires vigilant scanning of the environment and elevated tonic arousal levels. Our placebo manipulation consistently reduced vigilance measured in terms of undifferentiated reactivity to salient cues (indexed by subjective ratings, skin conductance responses and EEG event-related potentials) and tonic arousal [indexed by cue-unrelated skin conductance levels and enhanced EEG alpha (8–12 Hz) activity], indicating a downregulation of sustained anxiety rather than phasic fear. We also observed a placebo-dependent sustained increase of frontal midline EEG theta (4–7 Hz) power and frontoposterior theta coupling, suggesting the recruitment of frontally based cognitive control functions. Our results thus support the crucial role of treatment expectations in placebo anxiolysis and provide insight into the underlying neural mechanisms.

International audience; Insomniacs report decreased performance in daily routines, which may have detrimental consequences for car driving. We compared changes over time in driving performance (measured as Standard Deviation of Lateral Position – SDLP) and background EEG between 20 untreated insomnia patients (52–70 years old) and 21 normal sleepers (54–73 years old) during a 1 h on-the-road driving test after a normal night of sleep, in the morning. SDLP did not differ between groups and increased slightly over time to similar degrees in both groups. EEG alpha and beta power were lower in insomniacs as compared to normal sleepers. Alpha and beta power slightly reduced during driving in normal sleepers but remained at a constant low level in insomniacs. Changes in EEG power and SDLP were not related. It is concluded that on-the-road driving performance does not differ between older insomniacs and older normal sleepers and that changes in spectral EEG measures of cortical arousal and in driving performance are not related.

Working memory (WM) capacity affects our daily life in many ways, and its decrease often associates with neural disorders (e.g. Alzheimer's disease). Several studies have confirmed that alpha rhythms play an active role in memory mechanism. In the present study, we designed a digit verbal span experiment to find out that how the alpha power change during working memory encoding, and the relationship between alpha power and individual WM performance. Consistent with previous studies, our results confirm that alpha power is positively related to WM performance. Participants who had higher alpha power during WM encoding achieved better memory performance. We can conclude that the reason is alpha rhythms reflect inhibition of task-irrelevant information. Howbeit, a linear relationship between WM load and alpha power amplitude during memory encoding cannot be deduced in our experiment.