Oscillatory cortical activity during a motor task in a deafferented patient

Little is known about the influence of the afferent peripheral feedback on the sensorimotor cortex activation. To answer this open question we investigated the alpha and beta band task-related spectral power decreases (TRPow) in the deafferented patient G.L. and compared the results to those of six healthy subjects. The patient has been deafferented up to the nose for 24 years but her motor fibers are unaffected and she can perform complex motor tasks under visual control. We recorded EEG (58 scalp positions) as well as the exerted force during a visuomotor task. The subjects had to maintain in precision grip an isometric force at 15% of the maximal voluntary contraction. In the patient we found a significantly higher alpha band spectral power during rest and larger alpha TRPow decreases during the motor task when compared to the healthy subjects’ data. In contrast, we did not observe any significant differences between patient and controls for the beta band TRPow. The results indicate an altered functional alpha band network state in the patient, probably due to the chronic deafferentation leading to a deep ‘idling’ state of the contralateral sensorimotor area.     

Changes in alpha rhythm asymmetry during learning of verbal and visuospatial tasks.

Alpha activity in the two cortical hemispheres was examined during learning and overlearning of a verbal and a visuospatial task. Compared to a pretask baseline condition, the amount of alpha activity during the tasks was decreased. An increase in alpha activity was found from learning to overlearning in both tasks. A greater amount of alpha was found in the right hemisphere for both tasks. In addition, no difference in the degree of alpha asymmetry was found between the tasks. This was discussed in light of prior contrary findings. A significant positive correlation was found between change in learning rate and change in alpha asymmetry during the verbal task. An interpretation of this finding was offered in terms of the level of hemispheric activation reflecting the degree of task engagement.     

Sensory stimulation triggers spindles during sleep stage 2

STUDY OBJECTIVES: Toward understanding the function of sleep spindle, we examined whether sensory stimulation triggers sleep spindles. PARTICIPANTS: Eleven normal subjects participated in the experiments. INTERVENTION: The subjects had a nap in the afternoon, and sensory stimulation was applied during sleep stage 2. MEASUREMENTS: 21-channel EEG was recorded during the 2-3 hour experiment carried out between 13:00 and 16:00. Somatosensory, auditory, or visual stimulation was performed over a 5-minute period during stage 2. The frequency and duration of spindles were compared in 2 different segments of 5 minutes, with and without sensory stimulation. The latency from the onset of a sensory stimulus to the succeeding spindle was also analyzed. To estimate the active brain regions during a spindle, the EEG recordings were modeled with a single equivalent moving dipole (SEMD) model. RESULTS: In the period with stimulation, spindle frequency and duration increased compared with the period without stimulation. Statistical tests revealed that with stimulation, the interval between 2 consecutive spindles was significantly shorter (p < 0.05, regardless of the modality) and that the duration of the spindles was significantly longer with stimulation (p < 0.05, regardless of the modality). The latency was approximately 2 s. During a spindle after somatosensory stimulation brain activities were observed near the somatosensory area, while with auditory stimulation active regions were observed near the auditory cortex. CONCLUSIONS: A sensory stimulus appeared to trigger a sleep spindle during sleep stage 2. SEMD trajectories suggest that active brain regions during spindle are different according to the modality of the preceding stimulus.     

Effects of mental workload on long-latency auditory-evoked-potential,salivary cortisol,and immunoglobulin A

This paper researches on the effects of mental workload on long-latency auditory-evoked-potential (AEP), salivary cortisol, and immunoglobulin A (IgA). 20 Healthy subjects (11 males and 9 females) participated in the experiment voluntarily. The mental task consisted of two parts: arithmetic task and reading comprehension task. The Latencies of N1, P2, N2, P3, and mismatch negativity (MMN) all increased significantly after the mental tasks were adopted at all of the three recording sites: Cz, Fz, and Pz (p < 0.05). In this experiment, changes of salivary cortisol and s-IgA levels due to mental tasks were not significant. With the introduction of mental tasks, more processing resources are allocated to the primary task (mental task), and decreased processing resources available for the secondary task (auditory task), which is reflected on the increases in the latencies of probe-evoked AEP components.     

Event-Related Desynchronization evoked by auditory stimuli

Summary Event-Related Desynchronization (ERD) and Synchronization (ERS) of several EEG alpha frequencies was studied in 19 subjects during the presentation of linguistic and/or melodic auditory stimuli. The stimulus length was 1300 msec (+/–100 msec) and the interstimulus interval was 2000 msec. A significant ERD was found during auditory stimulation in the 8–10 Hz and 10–12 Hz alpha frequency bands, and there were also significant differences in the spatiotemporal pattern of the ERD between these frequency bands. Significant ERD was elicited also in the 10–11 and 11–12 Hz frequency bands by auditory stimulation. There were no significant differences between these one-hertz frequency bands. The subjects were assigned to two analysis groups according to their individual alpha peak frequency (10–11 or 11–12 Hz) at rest. The ERD in these groups reached statistical significance and there were significant differences between the groups. The ERD of the two groups differed significantly also when their EEG data was studied in the 10–12 Hz frequency band. The results from this study show that ERD is not modality-specific, i.e., it can be elicited also by auditory stimuli. Moreover, they indicate that it is important to control over interindividual variation in the EEG when studying the ERD phenomenon.This study was financially supported by the The Cultural Scholarship Foundation of Southwestern Finland (Varsinais-Suomen Kulttruurirahasto) and by the Council for Social Sciences, Academy of Finland (project 7338).     

Cerebral cortical dynamics during visuomotor transformation: adaptation to a cognitive-motor executive challenge

EEG was employed during cognitive-motor adaptation to a visuomotor transformation that required inhibition of an established motor plan. Performance was positively related to frontal alpha and theta power during both planning and execution of reaching movements to visual targets. EEG changes suggest initial involvement of frontal executive functioning to suppress established visuomotor mappings followed by progressive idling (i.e., alpha synchrony). Also, progressive idling of the temporal and parietal sites over the trials was observed, suggesting a decreasing role of working memory and encoding of the new visuomotor map, respectively. The regional changes in the cortical dynamics translated into the quality of motor behavior. This study expands our understanding of the role of frontal executive processes beyond the cognitive domain to the cognitive-motor domain.     

Effects of bromazepam in frontal theta activity on the performance of a sensorimotor integration task: A quantitative electroencephalography study

Our objective is to verify the modulatory effects of bromazepam on EEG theta absolute power when subjects were submitted to a visuomotor task (i.e., car driver task). Sample was composed of 14 students (9 males and 5 females), right handed, with ages varying between 23 and 42 years (mean = 32.5 ± 9.5), absence of mental or physical impairments, no psychoactive or psychotropic substance use and no neuromuscular disorders (screened by a clinical examination). The results showed an interaction between condition and electrodes (p = 0.034) in favor of F8 electrode compared with F7 in both experimental conditions (t-test; p = 0.001). Additionally, main effects were observed for condition (p = 0.001), period (p = 0.001) and electrodes (p = 0.031) in favor of F4 electrode compared with F3. In conclusion, Br 6 mg of bromazepam may interfere in sensorimotor processes in the task performance in an unpredictable scenario allowing that certain visuospatial factors were predominant. Therefore, the results may reflect that bromazepam effects influence the performance of the involved areas because of the acquisition and integration of sensory stimuli processes until the development of a motor behavior based on the same stimuli.     

Effect of working memory load on electrophysiological markers of visuospatial orienting in a spatial cueing task simulating a traffic situation

Visuospatial attentional orienting has typically been studied in abstract tasks with low ecological validity. However, real‐life tasks such as driving require allocation of working memory (WM) resources to several subtasks over and above orienting in a complex sensory environment. The aims of this study were twofold: firstly, to establish whether electrophysiological signatures of attentional orienting commonly observed under simplified task conditions generalize to a more naturalistic task situation with realistic‐looking stimuli, and, secondly, to assess how these signatures are affected by increased WM load under such conditions. Sixteen healthy participants performed a dual task consisting of a spatial cueing paradigm and a concurrent verbal memory task that simulated aspects of an actual traffic situation. Behaviorally, we observed a load‐induced detriment of sensitivity to targets. In the EEG, we replicated orienting‐related alpha lateralization, the lateralized ERPs ADAN, EDAN, and LDAP, and the P1‐N1 attention effect. When WM load was high (i.e., WM resources were reduced), lateralization of oscillatory activity in the lower alpha band was delayed. In the ERPs, we found that ADAN was also delayed, while EDAN was absent. Later ERP correlates were unaffected by load. Our results show that the findings in highly controlled artificial tasks can be generalized to spatial orienting in ecologically more valid tasks, and further suggest that the initiation of spatial orienting is delayed when WM demands of an unrelated secondary task are high.     

Spectra-temporal patterns underlying mental addition: An ERP and ERD/ERS study

Functional neuroimaging data have shown that mental calculation involves fronto-parietal areas that are composed of different subsystems shared with other cognitive functions such as working memory and language. Event-related potential (ERP) analysis has also indicated sequential information changes during the calculation process. However, little is known about the dynamic properties of oscillatory networks in this process. In the present study, we applied both ERP and event-related (de-)synchronization (ERS/ERD) analyses to EEG data recorded from normal human subjects performing tasks for sequential visual/auditory mental addition. Results in the study indicate that the late positive components (LPCs) can be decomposed into two separate parts. The earlier element LPC1 (around 360 ms) reflects the computing attribute and is more prominent in calculation tasks. The later element LPC2 (around 590 ms) indicates an effect of number size and appears larger only in a more complex 2-digit addition task. The theta ERS and alpha ERD show modality-independent frontal and parietal differential patterns between the mental addition and control groups, and discrepancies are noted in the beta ERD between the 2-digit and 1-digit mental addition groups. The 2-digit addition (both visual and auditory) results in similar beta ERD patterns to the auditory control, which may indicate a reliance on auditory-related resources in mental arithmetic, especially with increasing task difficulty. These results coincide with the theory of simple calculation relying on the visuospatial process and complex calculation depending on the phonological process.     

Effect of Self-Enhanced EEG Alpha on Performance and Mood After Two Nights of Sleep Loss

Can the deleterious effects of acute sleep loss on performance and mood be ameliorated by self-enhanced alpha activity? Fourteen Naval volunteers were divided equally into an experimental (alpha-contingent auditory feedback) group and a yoked control (pseudo feedback) group. All subjects received feedback plus performance and mood tests during 3 baseline days and following 2 days and 2 nights without sleep. Feedback was given for 45 min in the morning and 45 mm in the afternoon, preceding performance and mood tests. The self-enhanced alpha (experimental) subjects did produce more alpha than the yoked controls during all feedback sessions except for one pair that was discarded. Of eleven measures that were sensitive to deep loss, two performance scores and one mood score showed significantly less sleep-loss decrement for the self-enhanced alpha group (at the usual univariate. 05 level). Two recall scores and an anxiety score showed more impairment for the self-enhanced alpha group following sleep loss. The differences were not significant, however, by (he conservative Dunn-Bonferroni multivariate criterion, so our results are not conclusive. Alpha enhancement may help maintain performance that requires continuous attention, such us counting and auditory discrimination, but does not ameliorate the sleep-loss effect for anxiety, memory, and addition.     

Event-related desynchronization in the EEG during emotional and cognitive information processing: differential effects of extraversion

The aim of the present study was to analyze the influence of the personality dimension extraversion/introversion (E) on the level and topographical distribution of event-related desynchronization (ERD) in the EEG whilst participants were engaged in emotional face and cognitive information processing. In this context we build up on former studies dealing with the role of E as a possible moderator variable in cortical activation patterns during performance of mental speed, reasoning and working memory tasks (i.e., cognitive information processing). In a sample of 33 introverts and 33 extraverts (31 were male, 35 female) we found extraverted individuals displaying a lower (left-hemispheric) cortical activation than introverts when their task was to judge the identity of two simultaneously presented facial emotions. This effect was only observed in the upper alpha frequency band (9.6–11.6 Hz). In analyzing E differences during cognitive information processing (i.e., performance of a verbal and a figural-spatial task) E effects – which were moderated by participants’ sex – were restricted to lower EEG (alpha) frequency ranges (5.6–9.6 Hz). The results generally suggest that E is differently involved when different kinds of information are processed.     

Learning to multitask: effects of video game practice on electrophysiological indices of attention and resource allocation

Changes in attention allocation with complex task learning reflect processing automatization and more efficient control. We studied these changes using ERP and EEG spectral analyses in subjects playing Space Fortress, a complex video game comprising standard cognitive task components. We hypothesized that training would free up attentional resources for a secondary auditory oddball task. Both P3 and delta EEG showed a processing trade-off between game and oddball tasks, but only some game events showed reduced attention requirements with practice. Training magnified a transient increase in alpha power following both primary and secondary task events. This contrasted with alpha suppression observed when the oddball task was performed alone, suggesting that alpha may be related to attention switching. Hence, P3 and EEG spectral data are differentially sensitive to changes in attentional processing occurring with complex task training.     

Working memory capacity affects the interference control of distractors at auditory gating

It is important to understand the role of individual differences in working memory capacity (WMC). We investigated the relation between differences in WMC and N1 in event-related brain potentials as a measure of early selective attention for an auditory distractor in three-stimulus oddball tasks that required minimum memory. A high-WMC group (n = 13) showed a smaller N1 in response to a distractor and target than did a low-WMC group (n = 13) in the novel condition with high distraction. However, in the simple condition with low distraction, there was no difference in N1 between the groups. For all participants (n = 52), the correlation between the scores for WMC and N1 peak amplitude was strong for distractors in the novel condition, whereas there was no relation in the simple condition. These results suggest that WMC can predict the interference control for a salient distractor at auditory gating even during a selective attention task.     

Alpha amplitude and phase locking in obsessive-compulsive disorder during working memory

Alpha event-related desynchronization (ERD) and synchronization are known to reflect brain activation and inhibition, respectively. Alpha phase locking seems to reflect the timing in the cortical process. In a previous study, lower alpha ERD was related to working memory in obsessive-compulsive disorder (OCD) patients than in controls during the retention and retrival phases, but not in the encoding phase. However, memory deficits in OCD patients are known to be related to executive failure during the encoding phase. Thus, focusing on the encoding phase, we tested the level of alpha amplitude and phase locking in OCD patients according to memory load. The EEGs of fifteen OCD patients and fifteen controls were recorded during a Sternberg working memory task. The behavioral performance of the OCD patients was normal. However, the OCD group yielded significantly lower ERD and stronger phase locking. As memory load rose, ERD and phase locking significantly increased in both groups. A difference in event-related alpha oscillation was observed in the encoding phase. Lower alpha modulation in the OCD patient simplied abnormality of the excitatory/inhibitory process in the brain, and increased phase locking might reflect excessive attentional excitability.     

Prestimulus EEG alpha phase synchronicity influences N100 amplitude and reaction time

The influence of the level of prestimulus alpha phase synchronicity on the N100 component and reaction time (RT) was examined, in target auditory oddball data from 25 normal subjects. Alpha phase synchronicity is a new measure consisting (for a given stimulus presentation) of the angular or circular variance of the alpha phase at stimulus onset across the parieto-occipital sites. The lower the angular variance, the higher the phase synchronicity (the more closely in phase the alpha activity across these sites) and vice versa. Subaveraged event-related potentials (ERPs) were formed for high and low prestimulus alpha phase synchronicity stimulus presentations. N100 amplitude was significantly greater in the high than the low phase synchronicity subaverages. In addition, RT was significantly reduced in the high prestimulus alpha phase synchronicity cases. Alpha phase synchronicity reflects an aspect of brain state that influences subsequent stimulus processing.     

Deficient attention modulation of lateralized alpha power in schizophrenia

Modulation of 8–14 Hz (alpha) activity in posterior brain regions is associated with covert attention deployment in visuospatial tasks. Alpha power decrease contralateral to to‐be‐attended stimuli is believed to foster subsequent processing, such as retention of task‐relevant input. Degradation of this alpha‐regulation mechanism may reflect an early stage of disturbed attention regulation contributing to impaired attention and working memory commonly found in schizophrenia. The present study tested this hypothesis of early disturbed attention regulation by examining alpha power modulation in a lateralized cued delayed response task in 14 schizophrenia patients (SZ) and 25 healthy controls (HC). Participants were instructed to remember the location of a 100‐ms saccade‐target cue in the left or right visual hemifield in order to perform a delayed saccade to that location after a retention interval. As expected, alpha power decrease during the retention interval was larger in contralateral than ipsilateral posterior regions, and SZ showed less of this lateralization than did HC. In particular, SZ failed to show hemifield‐specific alpha modulation in posterior right hemisphere. Results suggest less efficient modulation of alpha oscillations that are considered critical for attention deployment and item encoding and, hence, may affect subsequent spatial working memory performance.     

Effects of mental tasks on the cardiorespiratory synchronization

The cardiovascular and respiratory systems are functionally related to each other, but it is unclear if the cerebral cortex can affect their interaction. The effect of a mental task on the synchronization between cardiovascular and respiratory systems was investigated in the article. Electroencephalogram (EEG), electrocardiogram (ECG) and respiratory signal (RES) were collected from 29 healthy male subjects during the mental arithmetic (MA) task and the synchrogram was used to estimate the strength of cardiorespiratory synchronization. Our results showed that MA task significantly increased the breath rate, the heart rate and the EEG power spectral energy in theta band at FC3, FC4 and C4 electrodes (p < 0.01), decreased the duration of cardiorespiratory synchronization epochs (p < 0.05). Moreover the duration of cardiorespiratory synchronization epochs during MA task was negatively correlated with the EEG power spectral energy in theta band at FC3, FC4 and C4 electrodes and the sympathetic activity (p < 0.05). The results demonstrated that ANS and cerebral cortex are implicated in the changes of cardiorespiratory synchronization during MA task.     

Theta oscillation during auditory change detection: An MEG study

To study the phase and power characteristics of brain oscillations during the preattentive detection of auditory deviance, we recorded magnetoencephalographic responses in 10 healthy subjects with an oddball paradigm. As the subject was watching a silent movie, standard tones (1000-Hz frequency, 100-ms duration) and their duration deviants (50-ms duration, probability of 15%) were randomly delivered binaurally. In addition to localizing the magnetic counterpart of mismatch negativity (MMNm) with equivalent current dipole modeling, we also measured the phase-locking value (PLV) and power change of the oscillatory responses to standard and deviant stimuli by employing the Morlet wavelet-based analysis. The MMNm signals peaking at 150-200 ms after the onset of deviant were localized in bilateral temporal regions with larger amplitudes in the right hemisphere. Then 50 ms after the onset of either standard or deviant stimuli, we observed an increase of PLV and power of theta and alpha oscillations in bilateral temporal regions. PLVs of theta and alpha activities to deviant stimuli were significantly larger in the right than left hemisphere (P < 0.001). Compared with standard stimuli, deviants elicited a larger theta PLV (P < 0.001) at 150-300 ms and a larger theta power change (P < 0.05) at 50-300 ms for the responses in the right temporal region. In addition, a prominent theta phase-locking of deviant-elicited responses was found in the right frontal area at 110-250 ms (P < 0.01). Our current data suggest that a pronounced phase and power modulation on sound-elicited theta oscillations might characterize the change detection processing in the temporo-frontal network as reflected by the mismatch negativity.     

A processing speed deficit in dyslexic adults? Evidence from a peg-moving task

Developmental dyslexia is diagnosed when literacy skills are not commensurate with a person's general cognitive ability and education. While the most common difficulty found in dyslexia is poor phonological processing, many dyslexics are reported to be clumsy, with poor handwriting, suggesting that there may be a motor deficit in dyslexia. To establish whether the motor difficulties described in dyslexic children persist into adulthood, we tested 18 dyslexic adults and 22 control participants on Annett's peg-moving task. The dyslexic participants performed significantly slower than control adults on the peg-moving task with their dominant hands (p = 0.004). Furthermore, response times (RTs) during tasks testing component literacy skills correlated with peg-moving ability in the dominant hand in the entire group (orthographic r = 0.448, p = 0.005; phonological r = 0.383, p = 0.025). These results indicate that a motor speed deficit in dyslexia may not be simply a sign of developmental delay, but may persist into adulthood. Furthermore, motor speed may be related to the speed at which literacy information is processed.     

Effects of stimulus-independent oculomotor activity on the occipital EEG

In order to assess the effects of oculomotor activity on the occipital alpha rhythm, 24 subjects performed each of 2 instructed tasks — random eye movement and eye movement suppression — under conditions of darkness (with eyes both open and closed) and illumination (eyes open in a Ganzfeld). Recordings of the occipital EEG indicated a general blocking of alpha during periods of oculomotor activity for 2 dependent measures, percent time alpha and mean duration of alpha bursts, by comparison with baseline intervals of relaxation. These results are interpreted as support for the activating effects of efferent, oculomotor processes on the alpha component of the EEG.