Human EEG, behavioral stillness and biofeedback

Selective cortical adaptations associated with neural efficiency in visuospatial tasks - the comparison of electroencephalographic profiles of expert and novice artists

Visuospatial cognition encapsulates an individual's ability to efficiently navigate and make sense of the multimodal cues from their surroundings, and therefore has been linked to expert performance across multiple domains, including sports, performing arts, and highly skilled tasks, such as drawing (Morrone and Minini, 2023). As neural efficiency posits a task-specific functional reorganization facilitated by long-term training, the present study employs a visuospatial construction task as a means of investigating the neurophysiological adaptations associated with expert visuospatial cognitive performance. Electroencephalogram (EEG) data acquisitions were used to evaluate the event-related changes (ER%) and statistical topographic maps of nine expert versus nine novice artists. The expert artists displayed overall higher global ER% compared to the novices within task-active intervals. Significant increases in relative ER% were found in the theta (t (10) = 3.528, p = 0.003, CI = [27.3,120.9]), lower-alpha (t (10) = 3.751, p = 0.002, CI = [28.2,110.5]), upper-alpha (t (10) = 3.829, p = 0.002, CI = [50.2,189.8]), and low beta (t (10) = 4.342, p < 0.001, CI = [37.0,114.9]) frequency bands, when comparing the experts to the novice participants. These results were particularly found in the frontal (t (14) = 2.014, p = 0.032, CI = [7.7,245.4]) and occipital (t (14) = 2.647, p = 0.010, CI = [45.0,429.7]) regions. Further, a significant decrease in alpha ER% from lower to upper activity (t (8) = 4.475, p = 0.001, CI = [21.0, 65.8]) was found across cortical regions in the novice group. Notably, greater deviation between lower and upper-alpha activity was found across scalp locations in the novice group, compared to the experts. Overall, the findings demonstrate potential local and global EEG-based indices of selective cortical adaptations within a task requiring a high degree of visuospatial cognition, although further work is needed to replicate these findings across other domains.

The Effect of Mobile Neurofeedback Training in Children with Attention Deficit Hyperactivity Disorder: A Randomized Controlled Trial

Objective

: To examine the effect of mobile neurofeedback training on the clinical symptoms, attention abilities, and execution functions of children with attention deficit hyperactivity disorder (ADHD).

Methods

: The participants were 74 children with ADHD aged 8-15 years who visited the Department of Child and Adolescent Psychiatry at Seoul National University Children's Hospital. The participants were randomly assigned to the mobile neurofeedback (n = 35) or control (sham; n = 39) group. Neurofeedback training was administered using a mobile app (equipped with a headset with a 2-channel electroencephalogram [EEG] sensor) for 30 min/day, 3 days/week, for 3 months. Children with ADHD were individually administered various neuropsychological tests, including the continuous performance test, Children's Color Trails Test-1 and 2, and Stroop Color and Word Tests. The effects of mobile neurofeedback were evaluated at baseline and at 3 and 6 months after treatment initiation.

Results

: Following treatment, both mobile neurofeedback-only and sham-only groups showed significant improvements in attention and response inhibition. In the visual continuous performance test, omission errors decreased to the normal range in the mobile neurofeedback-only group after training, suggesting that mobile neurofeedback effectively reduced inattention in children with ADHD. In the advanced test of attention, auditory response times decreased in the mobile neurofeedback + medication group after training, but increased in the sham+medication group. Overall, there were no significant between-group differences in other performance outcomes.

Conclusion

: Mobile neurofeedback may have potential as an additional therapeutic option alongside medication for children with ADHD.

Electrical Brain Activity during Human Walking with Parametric Variations in Terrain Unevenness and Walking Speed

Mobile brain imaging with high-density electroencephalography (EEG) can provide insight into the cortical processes involved in complex human walking tasks. While uneven terrain is common in the natural environment and poses challenges to human balance control, there is limited understanding of the supraspinal processes involved with traversing uneven terrain. The primary objective of this study was to quantify electrocortical activity related to parametric variations in terrain unevenness for neurotypical young adults. We used high-density EEG to measure brain activity when thirty-two young adults walked on a novel custom-made uneven terrain treadmill surface with four levels of difficulty at a walking speed tailored to each participant. We identified multiple brain regions associated with uneven terrain walking. Alpha (8 - 13 Hz) and beta (13 - 30 Hz) spectral power decreased in the sensorimotor and posterior parietal areas with increasing terrain unevenness while theta (4 - 8 Hz) power increased in the mid/posterior cingulate area with terrain unevenness. We also found that within stride spectral power fluctuations increased with terrain unevenness. Our secondary goal was to investigate the effect of parametric changes in walking speed (0.25 m/s, 0.5m/s, 0.75 m/s, 1.0 m/s) to differentiate the effects of walking speed from uneven terrain. Our results revealed that electrocortical activities only changed substantially with speed within the sensorimotor area but not in other brain areas. Together, these results indicate there are distinct cortical processes contributing to the control of walking over uneven terrain versus modulation of walking speed on smooth, flat terrain. Our findings increase our understanding of cortical involvement in an ecologically valid walking task and could serve as a benchmark for identifying deficits in cortical dynamics that occur in people with mobility deficits.

Managing anxiety disorders with the neuro-biofeedback method of Brain Boy Universal Professional

Background

Biofeedback is a non-invasive therapeutic method used independently or as an adjunct alongside other methods.

Objective

This study evaluated the efficacy of biofeedback in the treatment of anxiety disorders.

Methods

The sample consisted of 85 individuals with anxiety symptoms who underwent neuro-biofeedback therapy using Brain Boy Universal Professional. Anxiety was assessed by both the Hamilton Rating Scale for Anxiety (HAM-A) and Zung Anxiety Self-Assessment Scale (SAS) before the initiation and after completing ten sessions with biofeedback.

Results

Before biofeedback and based on the HAM-A scale, 27.0% of the individuals showed mild to moderate anxiety, 16.5% medium anxiety, and 56.5% severe anxiety. After the completion of biofeedback, 90.6% of the individuals experienced mild to moderate anxiety, 5.9% medium anxiety, and 3.5% severe anxiety. Based on the SAS scale, before biofeedback, 42.4% of the individuals showed minimal to moderate anxiety, 21.2% marked severe anxiety and 36.5% most extreme anxiety. After the biofeedback, 68.2% of the individuals were within a normal range, 27.1% had minimal to moderate anxiety, 4.7% marked severe anxiety, and none in most extreme anxiety.

Conclusion

Both HAMA-A and SAS scales showed statistically reduced anxiety levels after biofeedback therapy. Thus, the primary symptom of anxiety can be addressed by the biofeedback method.

Identifying electrophysiological markers of autism spectrum disorder and schizophrenia against a backdrop of normal brain development

An examination of electroencephalographic and magnetoencephalographic studies demonstrates how age-related changes in brain neural function temporally constrain their use as diagnostic markers. A first example shows that, given maturational changes in the resting-state peak alpha frequency in typically developing children but not in children who have autism spectrum disorder (ASD), group differences in alpha-band activity characterize only a subset of children who have ASD. A second example, auditory encoding processes in schizophrenia, shows that the complication of normal age-related brain changes on detecting and interpreting group differences in neural activity is not specific to children. MRI studies reporting group differences in the rate of brain maturation demonstrate that a group difference in brain maturation may be a concern for all diagnostic brain markers. Attention to brain maturation is needed whether one takes a DSM-5 or a Research Domain Criteria approach to research. For example, although there is interest in cross-diagnostic studies comparing brain measures in ASD and schizophrenia, such studies are difficult given that measures are obtained in one group well after and in the other much closer to the onset of symptoms. In addition, given differences in brain activity among infants, toddlers, children, adolescents, and younger and older adults, creating tasks and research designs that produce interpretable findings across the life span and yet allow for development is difficult at best. To conclude, brain imaging findings show an effect of brain maturation on diagnostic markers separate from (and potentially difficult to distinguish from) effects of disease processes. Available research with large samples already provides direction about the age range(s) when diagnostic markers are most robust and informative.

Individual EEG alpha profiles are gender-dependent and indicate subjective experiences in Whole-Body Perceptual Deprivation

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 L < R) or negative (frontal L > R) affect; a more verbal (L > R) or a more imagistic (R > L) mode of thinking; and a more trancelike (frontal > parietal) or more reflective (frontal < parietal) 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 R > L asymmetry found for male participants, and a predominant L > R asymmetry found for female participants.

Electrophysiological CNS-processes related to associative learning in humans

The neurophysiology of human associative memory has been studied with electroencephalographic techniques since the 1930s. This research has revealed that different types of electrophysiological processes in the human brain can be modified by conditioning: sensory evoked potentials, sensory induced gamma-band activity, periods of frequency-specific waves (alpha and beta waves, the sensorimotor rhythm and the mu-rhythm) and slow cortical potentials. Conditioning of these processes has been studied in experiments that either use operant conditioning or repeated contingent pairings of conditioned and unconditioned stimuli (classical conditioning). In operant conditioning, the appearance of a specific brain process is paired with an external stimulus (neurofeedback) and the feedback enables subjects to obtain varying degrees of control of the CNS-process. Such acquired self-regulation of brain activity has found practical uses for instance in the amelioration of epileptic seizures, Autism Spectrum Disorders (ASD) and Attention Deficit Hyperactivity Disorder (ADHD). It has also provided communicative means of assistance for tetraplegic patients through the use of brain computer interfaces. Both extra and intracortically recorded signals have been coupled with contingent external feedback. It is the aim for this review to summarize essential results on all types of electromagnetic brain processes that have been modified by classical or operant conditioning. The results are organized according to type of conditioned EEG-process, type of conditioning, and sensory modalities of the conditioning stimuli.

Repetitive Transcorneal Alternating Current Stimulation Reduces Brain Idling State After Long-term Vision Loss

BACKGROUND

Deafferentation of visual system structures following brain or optic nerve injury leaves cortical areas deprived of visual input. Deprived cortical areas have a reduced sensory information processing and are characterized with localized enhanced or synchronized rhythms believed to represent an "idling state".

OBJECTIVE/HYPOTHESIS

We hypothesized that cortical idling can be modified with transcorneal alternating current stimulation (tACS) known to modulate cortical oscillations and thus change the functional state of the deafferented areas.

METHODS

tACS was applied in rat model of severe optic nerve crush using a protocol similar to our clinical studies (200 μA, 2-8 Hz) for 5 treatment days right after the lesion and at the chronic stage (3 months later). EEG and VEP were recorded over the visual cortices. In vivo confocal neuroimaging of the retina and histology of the optic nerves were performed.

RESULTS

Morphological investigations showed massive retinal ganglion cells death and degeneration of the optic nerves after crush. Visual loss was associated with increased EEG spectral power and lower coherence, indicating an "idling state". Stimulation induced a significant decrease of EEG power towards normal values. These effects were especially pronounced in the chronic stage.

CONCLUSION

Our results suggest that alternating current injected via the eye is able to modulate visually deprived brain areas and thus reduce cortical idling.

The origin of the audiovisual bounce inducing effect: a TMS study

The audiovisual bounce inducing effect (ABE) is a bouncing percept induced by the presence of a sound at the moment of two moving objects intercepting in a motion display otherwise perceived as streaming. The origin of the ABE is still debated: the effect could arise from the subtraction of attentional resources caused by the sound (needed to favor the perception of streaming), and/or from the cross-modal integration (binding) of visual and auditory information: indeed bouncing-like sounds are best in inducing the ABE. The neural mechanism responsible for the ABE is still unknown. Here, by using offline TMS, we investigated the role of the posterior parietal cortex (PPC), thought to be involved in both attentional and binding processes, in the generation of the ABE. Results show that disrupting the functional integrity of the right (but not the left) PPC has the effect of weakening the binding of cross-modal information, which reduces the magnitude of the ABE. Indeed, if the effect of parietal stimulation was merely to disrupt attention, we would expect an increase (not a decrease) of bouncing percepts. The present study not only shows the involvement of the right PPC in the ABE, but also support the notion that cross-modal binding (and not attention) is at the origin of the ABE.

Development of mu rhythm in infants and preschool children

Mu rhythm is an idling rhythm that originates in the sensorimotor cortex during rest. The frequency of mu rhythm, which is well established in adults, is 8-12 Hz, whereas the limited results available from children suggest a frequency as low as 5.4 Hz at 6 months of age, which gradually increases to the adult value. Understanding the normal development of mu rhythm has important theoretical and clinical implications since we still know very little about this signal in infants and how it develops with age. We measured mu rhythm over the left hemisphere using a pediatric magnetoencephalography (MEG) system in 25 infants (11-47 weeks), 18 preschool children (2-5 years) and 6 adults (20-39 years) for two 5-min sessions during two intermixed conditions: a rest condition in which the hands were at rest, and a prehension condition in which the subject squeezed a pipette with his/her right hand. In all participants, mu rhythm was present over the frontoparietal area during the rest condition, but was clearly suppressed during the prehension condition. Mu rhythm peak frequency, determined from the amplitude spectra, increased rapidly as a function of age from 2.75 Hz at 11 weeks to 8.25 Hz at 47 weeks (r2 = 0.83). It increased very slowly during the preschool period (3.1 ± 0.9 years; 8.5 ± 0.54 Hz). The frequency in these children was, however, lower than in adults (10.3 ± 1.2 Hz). Our results show a rapid maturation in spontaneous mu rhythm during the first year of life.

A cognitive and neurophysiological test of change from an individual's baseline

OBJECTIVE

An automated cognitive neurophysiological test is presented that characterizes how an individual was affected by a drug or treatment. The test calculates sub-scores for working memory task performance, cortical activation, and alertness, and combines the sub-scores into an overall score.

METHODS

The test was applied in a double-blind, placebo-controlled study of alcohol, caffeine, diphenhydramine, and sleep deprivation in 16 healthy adults.

RESULTS

The between- and within-day variability of the sub-scores and overall scores for placebo were all near zero, suggesting that the scores are stable. All treatments affected the overall score, while differential effects on sub-scores highlighted the added value of EEG measures.

CONCLUSIONS

The test is sensitive to relatively mild alterations in cognitive function. Its automation makes it suitable for use in large-scale clinical trials.

SIGNIFICANCE

By combining task performance with EEG brain function measures, the test may prove to have better sensitivity and specificity in detecting changes due to drugs or other treatments than comparable neuropsychological test batteries that do not directly measure brain function signals.

Athletes Are Different: Factors That Differentiate Biofeedback/Neurofeedback for Sport Versus Clinical Practice

Biofeedback and neurofeedback training procedures are often different for athletes than for clinical patients. Athletes come to improve performance whereas patients come to reduce symptoms. This article outlines factors that distinguish work with athletes from work with clinical patients. The differences in training include the purpose of training, the nature of the participant in training, session design, and covert factors underlying the training. Unlike clients, athletes often do intensive transfer of learning training, between 2 and 6 hours of daily sport practice across days, weeks, and months. Although biofeedback and neurofeedback are important factors for enhancing peak performance, there are many covert and overt factors producing performance success such as motivation, intensity of training, “A-ha” experiences, experimental expectancy, behavioral consequences, and mastery learning. The training process with athletes is illustrated through a case example of a young tennis player who mastered control of his anger.

Neurofeedback Effects on Evoked and Induced EEG Gamma Band Reactivity to Drug-related Cues in Cocaine Addiction

INTRODUCTION: Preoccupation with drug and drug-related items is a typical characteristic of cocaine addicted individuals. It has been shown in multiple accounts that prolonged drug use has a profound effect on the EEG recordings of drug addicts when compared to controls during cue reactivity tests. Cue reactivity refers to a phenomenon in which individuals with a history of drug abuse exhibit excessive psychophysiological responses to cues associated with their drug of choice. One of the aims of this pilot study was to determine the presence of an attentional bias to preferentially process drug-related cues using evoked and induced gamma reactivity measures in cocaine addicts before and after biobehavioral treatment based on neurofeedback. Another aim was to show that central SMR amplitude increase and frontal theta control is possible in an experimental outpatient drug users group over 12 neurofeedback sessions. METHOD: Ten current cocaine abusers participated in this pilot research study using neurofeedback combined with Motivational Interviewing sessions. Eight of them completed all planned pre- and post -neurofeedback cue reactivity tests with event-related EEG recording and clinical evaluations. Cue reactivity test represented a visual oddball task with images from the International Affective Picture System and drug-related pictures. Evoked and induced gamma responses to target and non-target drug cues were analyzed using wavelet analysis. RESULTS: Outpatient subjects with cocaine addiction completed the biobehavioral intervention and successfully increased SMR while keeping theta practically unchanged in 12 sessions of neurofeedback training. The addition of Motivational Interviewing helped retain patients in the study. Clinical evaluations immediately after completion of the treatment showed decreased self-reports on depression and stress scores, and urine tests collaborated reports of decreased use of cocaine and marijuana. Effects of neurofeedback resulted in a lower EEG gamma reactivity to drug-related images in a post-neurofeedback cue reactivity test. In particular, evoked gamma showed decreases in power to non-target and to a lesser extent target drug-related cues at all topographies (left, right, frontal, parietal, medial, inferior); while induced gamma power decreased globally to both target and non-target drug cues. Our findings supported our hypothesis that gamma band cue reactivity measures are sufficiently sensitive functional outcomes of neurofeedback treatment. Both evoked and induced gamma measures were found capable to detect changes in responsiveness to both target and non-target drug cues. CONCLUSION: Our study emphasizes the utility of cognitive neuroscience methods based on EEG gamma band measures for the assessment of the functional outcomes of neurofeedback-based biobehavioral interventions for cocaine use disorders. This approach may have significant potential for identifying both physiological and clinical markers of treatment progress. The results confirmed our prediction that EEG changes achieved with neurofeedback training will be accompanied by positive EEG outcomes in a cue reactivity and clinical improvements.

The nature of individual differences in EEG parameters during homogeneous visual field in 5- and 6-year-old twins: a pilot study

OBJECTIVE

To assess the genetic and environmental influences on the inter-individual variability of spectral EEG parameters under two conditions of reduced visual input in preschoolers.

METHODS

EEG was recorded in 21 monozygotic and 20 same-sex dizygotic twin pairs aged 5-6 years under the Closed eyes and Darkness conditions. The contributions of genetic and environmental influences to individual EEG parameters were estimated using structural equation modeling.

RESULTS

The alpha rhythm parameters - both spectral amplitude and frequency - were influenced mainly by genetic factors. Theta spectral amplitude variance was presumably accounted for by both genetic and shared environmental factors. The difference in the nature of population variance between EEG alpha and theta band spectral amplitudes was reproduced for two identical functional loads: Closed eyes and Darkness.

CONCLUSIONS

The majority of EEG spectral parameters in preschool children are determined by genetic factors. Tentative finding on systematic environmental influences on theta spectral amplitude under the condition of reduced visual input may point to the role of experience in the individual differences in the functioning of theta response system.

SIGNIFICANCE

The findings contribute to the scanty knowledge about the heritability of EEG rhythms in preschool children.

Modulation of cortical oscillatory activity during transcranial magnetic stimulation

Transcranial magnetic stimulation (TMS) can transiently modulate cortical excitability, with a net effect depending on the stimulation frequency (< or =1 Hz inhibition vs. > or =5 Hz facilitation, at least for the motor cortex). This possibility has generated interest in experiments aiming to improve deficits in clinical settings, as well as deficits in the cognitive domain. The aim of the present study was to investigate the on-line effects of low frequency (1 Hz) TMS on the EEG oscillatory activity in the healthy human brain, focusing particularly on the outcome of these modulatory effects in relation to the duration of the TMS stimulation. To this end, we used the event-related desynchronization/synchronization (ERD/ERS) approach to determine the patterns of oscillatory activity during two consecutive trains of sham and real TMS. Each train of stimulation was delivered to the left primary motor cortex (MI) of healthy subjects over a period of 10 min, while EEG rhythms were simultaneously recorded. Results indicated that TMS induced an increase in the power of brain rhythms that was related to the period of the stimulation, i.e. the synchronization of the alpha band increased with the duration of the stimulation, and this increase was inversely correlated with motor-evoked potentials (MEPs) amplitude. In conclusion, low frequency TMS over primary motor cortex induces a synchronization of the background oscillatory activity on the stimulated region. This induced modulation in brain oscillations seems to increase coherently with the duration of stimulation, suggesting that TMS effects may involve short-term modification of the neural circuitry sustaining MEPs characteristics.

Effects of concurrent visual tasks on cortico-muscular synchronization in humans

To study the effects of external visual stimulation on motor cortex-muscle synchronization, coherence between electroencephalography (EEG) and electromyography (EMG) was measured in normal subjects under Before, Task (visual task: Ignore or Count, or arithmetic task) and After conditions. The control (Before and After) conditions required the subject to maintain first dorsal interosseous muscle contraction without visual stimulation. In the visual task, a random series of visual stimuli were displayed on a screen while the subjects maintained the muscle contraction. The subjects were asked to ignore the stimuli in the Ignore condition and to count certain stimuli in the Count condition. Also, in the arithmetic task, the subjects were asked to perform a simple subtraction. The EEG-EMG coherence found at C(3) site at 13-30 Hz (beta) was increased and sustained in magnitude during the Ignore and Count conditions, respectively. To examine the cause of the change of coherence, changes of EEG and EMG spectral power were computed for each frequency band. There was little change in the EMG spectral power in any frequency bands. While the spectral power of EEG unchanged in the beta band, it significantly increased and decreased in the range of 8-12 Hz and of 31-50 Hz, respectively, for both Ignore and Count conditions, not only at the C(3) site but at various sites as well. These results were in contrast to those obtained for the arithmetic task: the beta band EEG-EMG coherence was attenuated and the EEG spectral power at 4-7 Hz and at 31-50 Hz were significantly increased and decreased, respectively. As a conclusion, the present results are consistent with the idea that the enhanced 8-12 Hz/decreased 31-50 Hz oscillations affect strength of the beta band cortico-muscular synchronization by suppressing the visual processing.

Metabolic and electric brain patterns during pleasant and unpleasant emotions induced by music masterpieces

Brain correlates comparing pleasant and unpleasant states induced by three dissimilar masterpiece excerpts were obtained. Related emotional reactions to the music were studied using Principal Component Analysis of validated reports, fMRI, and EEG coherent activity. A piano selection by Bach and a symphonic passage from Mahler widely differing in musical features were used as pleasing pieces. A segment by Prodromidès was used as an unpleasing stimulus. Ten consecutive 30 s segments of each piece alternating with random static noise were played to 19 non-musician volunteers for a total of 30 min of auditory stimulation. Both brain approaches identified a left cortical network involved with pleasant feelings (Bach and Mahler vs. Prodromidès) including the left primary auditory area, posterior temporal, inferior parietal and prefrontal regions. While the primary auditory zone may provide an early affective quality, left cognitive areas may contribute to pleasant feelings when melodic sequences follow expected rules. In contrast, unpleasant emotions (Prodromidès vs. Bach and Mahler) involved the activation of the right frontopolar and paralimbic areas. Left activation with pleasant and right with unpleasant musical feelings is consistent with right supremacy in novel situations and left in predictable processes. When all musical excerpts were jointly compared to noise, in addition to bilateral auditory activation, the left temporal pole, inferior frontal gyrus, and frontopolar area were activated suggesting that cognitive and language processes were recruited in general responses to music. Sensory and cognitive integration seems required for musical emotion.

ERD/ERS patterns reflecting sensorimotor activation and deactivation

Oscillations in the alpha and beta band (<35 Hz) show characteristic spatiotemporal patterns during sensorimotor processing. Whereas event-related desynchronization (ERD) during motor preparation, execution, and imagery can be seen as a correlate of an activated cortical area, event-related synchronization (ERS) of frequency components between 10 and 13 Hz may represent a deactivated cortical area or inhibited cortical network, at least under certain conditions. Induced beta rhythms (13-35 Hz, beta ERS) can be found in sensorimotor areas following both voluntary movement and somatosensory stimulation. In a recent study we used different tasks involving execution and imagery of movements of the upper and lower limb to produce activation vs. deactivation/inhibition of the sensorimotor hand area. Sensorimotor interference, as a function of the activation level of the motor cortex, was studied by the use of repetitive median nerve stimulation (MNS) (ISI 1.5 s) in 12 healthy volunteers during the following task conditions: (i) cube manipulation between thumb and fingers of one hand, (ii) imagined cube manipulation, (iii) continuous foot rotation movements, and (iv) imagined foot movements. EEG was recorded from hand and foot representation areas and processed time-locked to MNS (ERD/ERS). In addition, task-related band power changes (TRPD/TRPI) were analyzed. We found a clear-cut suppression of the stimulation-induced beta ERS (indicating an enhanced activity state of the sensorimotor areas) during active cube manipulation and a weaker suppression during cube imagery. Mental imagination of foot movement led to an increase of the hand area mu rhythm, but did not interfere with stimulation-related effects on beta ERS. These findings support that interfering sensorimotor activation and deactivation is reflected in graduated changes of induced mu and beta oscillations.

The functional significance of mu rhythms: translating "seeing" and "hearing" into "doing"

Existing evidence indicates that mu and other alpha-like rhythms are independent phenomena because of differences in source generation, sensitivity to sensory events, bilateral coherence, frequency, and power. Although mu suppression and enhancement echo sensorimotor processing in frontoparietal networks, they are also sensitive to cognitive and affective influences and likely reflect more than an idling brain state. Mu rhythms are present at early stages of human development and in other mammalian species. They exhibit adaptive and dynamically changing properties, including frequency acceleration and posterior-to-anterior shifts in focus. Furthermore, individuals can learn to control mu rhythms volitionally in a very short period of time. This raises questions about the mu rhythm's open neural architecture and ability to respond to cognitive, affective, and motor imagery, implying an even greater developmental and functional role than has previously been ascribed to it. Recent studies have suggested that mu rhythms reflect downstream modulation of motor cortex by prefrontal mirror neurons, i.e., cells that may play a critical role in imitation learning and the ability to understand the actions of others. It is proposed that mu rhythms represent an important information processing function that links perception and action-specifically, the transformation of "seeing" and "hearing" into "doing." In a broader context, this transformation function results from an entrainment/gating mechanism in which multiple alpha networks (visual-, auditory-, and somatosensory-centered domains), typically producing rhythmic oscillations in a locally independent manner, become coupled and entrained. A global or 'diffuse and distributed alpha system' comes into existence when these independent sources of alpha become coherently engaged in transforming perception to action.

Heritability and "environmentability" of electroencephalogram in infants: the twin study

We estimated relative contribution of genetic and environmental factors to electroencephalogram (EEG) frequency and amplitude parameters in infants. EEG was registered in 49 pairs of monozygotic and 45 pairs of dizygotic twins aged 7-12 months during (1) visual attention and (2) darkness. The variability of occipital alpha frequency depended mainly on genetic, probably nonadditive factors. The mean heritability for the spectral amplitudes in the delta, theta, and alpha bands were 0.37, 0.13, and 0.22 during visual attention, and 0.22, 0.40, and 0.10 during darkness. The influence of shared environment was probable for many of the EEG parameters. It was greatest for the amplitude of the theta rhythm during visual attention. The theta amplitude depended on such a parameter of early social environmental enrichment as the number of caregivers in the family. The possible relationship between infant theta rhythm and developmental outcome is discussed. For many of the EEG parameters, heritability increased during the second half of the first year of life, thus supporting the hypothesis about amplification of genetic effects and decrease of common environmental influences with age.

Induced Oscillations in the Alpha Band: Functional Meaning

The phenomena of event-related desynchronization (ERD) and synchronization (ERS) reflect the dynamics of neural networks and can be observed on different scalp locations at the same moment of time. Whereas on one cortical area a focal 10-Hz ERD can be found, other areas can display a 10-Hz ERS. This phenomenon is called focal ERD/surround ERS and is interpreted as a correlate of an activated cortical area (ERD) and simultaneously deactivated or inhibited other areas. The induced oscillations (ERS) are dominant in the 10- to 13-Hz band and very likely mediated by thalamic gating.

Impairment of post-movement beta synchronisation in parkinson's disease is related to laterality of tremor

OBJECTIVE

Post-movement beta synchronisation (PMBS) is a physiological indicator of the activity of movement related neural networks. To investigate the pathophysiology of this phenomenon, we examined its characteristics in patients with unilateral tremor-dominant Parkinson's disease (PD).

METHODS

Movement duration and PMBS was measured after self-paced movement of the thumb at movement-reactive beta frequencies, over the supplementary motor area in 10 PD patients and 8 control subjects.

RESULTS

Movement duration in PD patients was longer than in controls. In left hand tremor patients, movement of the left hand was significantly longer compared to the right hand. When PD patients moved their non-affected hand, similarly to the controls, PMBS was higher contralateral to the movement. After movement of the tremulous hand, the contralateral PMBS decreased significantly and the contralateral preponderance disappeared. In the same hemisphere, PMBS was higher after contralateral to the non-affected hand movement, than after ipsilateral to the tremulous hand after movement.

CONCLUSIONS

PMBS in PD is affected by the activity of tremor related neural networks, suggesting that both cortical and subcortical sources are responsible for its generation. Examination of PMBS in various neurological diseases might provide further data on its physiological significance.

Inhibitory control of acquired motor programmes in the human brain

An important basis of skilled human behaviour is the appropriate retrieval of acquired and memorized motor programmes ('motor memory traces'). Appropriate retrieval is warranted if motor programmes are only activated if necessary and are, probably more often, inhibited if required by the context of a given situation. It is unknown how this type of inhibition is accomplished in the brain. We studied context-dependent modulation of motor memory traces in 18 volunteers and six patients with focal dystonia. Cortical function was assessed with transcranial magnetic stimulation over the primary motor cortex (M1) and with task-related analysis of oscillatory EEG activity. An activation (ACT) and inhibition (INH) condition were compared. In both, visual cues were presented at 1/s. In ACT, subjects had to respond to these cues with individual finger movements as learned in a preceding training session. In INH, subjects had to observe the cues without retrieval of motor responses. During INH, inhibitory control of the motor memory trace was confirmed by significant amplitude reduction of motor evoked potentials (MEPs) compared with baseline. This was accompanied by a significant increase of 11-13 Hz oscillatory activity over the sensorimotor areas during INH. During active retrieval of the motor memory traces, the reverse was true (increased MEP amplitudes, decreased oscillatory 11-13 Hz activity). In a small sample of dystonic patients (n = 6), the increase of 11-13 Hz oscillatory activity during INH was consistently absent. The present data demonstrate for the first time cortical correlates of appropriate, context-dependent inhibition of motor memory traces. We propose that focal increases of oscillatory activity are instrumental for inhibitory control at the cortical level. This concept is supported by the preliminary observations in dystonic patients who are known to have deficits of inhibitory motor control and in whom these context-dependent focal increases of oscillatory activity were absent.

Human electrophysiological and cognitive effects of exposure to ELF magnetic and ELF modulated RF and microwave fields: a review of recent studies

The investigation of weak (<500 microT), extremely low frequency (ELF, 0-300 Hz) magnetic field (MF) exposure upon human cognition and electrophysiology has yielded incomplete and contradictory evidence that MFs interact with human biology. This may be due to the small number of studies undertaken examining ELF MF effects upon the human electroencephalogram (EEG), and the associated analysis of evoked related potentials (ERPs). Relatively few studies have examined how MF exposure may affect cognitive and perceptual processing in human subjects. The introduction of this review considers some of the recent studies of ELF MF exposure upon the EEG, ERPs and cognitive and perceptual tasks. We also consider some of the confounding factors within current human MF studies and suggest some new strategies for further experimentation.

The role of the left temporal region under the cognitive motor demands of shooting in skilled marksmen

A number of investigators have reported elevated left temporal alpha power in marksmen during response preparation. This finding has been interpreted to indicate the suppression of irrelevant cognitive processes. However, lower-order motor processes have not been excluded as a possible explanation. Event-related alpha power (11-13 Hz) was examined at sites T3, T4, C3, and C4 in eight skilled marksmen during shooting and two control tasks varying in perceptual-motor complexity. Over an 8-s period preceding the trigger pull, the marksmen exhibited higher power and slope at T3 than at all other sites during shooting compared with the control conditions. No such difference between conditions was detected at C3 and C4. The relative synchrony of left temporal alpha power during shooting, in conjunction with the lack of change at central sites, is inconsistent with the explanation that the effect is accounted for by 'lower-order' motor processes exclusively involving the central region.

Autonomic and EEG patterns distinguish transcending from other experiences during Transcendental Meditation practice

This study compared EEG and autonomic patterns during transcending to "other" experiences during Transcendental Meditation (TM) practice. To correlate specific meditation experiences with physiological measures, the experimenter rang a bell three times during the TM session. Subjects categorized their experiences around each bell ring. Transcending, in comparison to "other" experiences during TM practice, was marked by: (1) significantly lower breath rates; (2) higher respiratory sinus arrhythmia amplitudes; (3) higher EEG alpha amplitude; and (4) higher alpha coherence. In addition, skin conductance responses to the experimenter-initiated bell rings were larger during transcending. These findings suggest that monitoring patterns of physiological variables may index dynamically changing inner experiences during meditation practice. This could allow a more precise investigation into the nature of meditation experiences and a more accurate comparison of meditation states with other eyes-closed conditions.

Alpha activity as an index of cortical inhibition during sustained internally controlled attention in infants

OBJECTIVES

The study examined the suggestion that infant ability to maintain attention in anticipatory task and to sustain interference is related to the active inhibitory processes in cortical neural networks.

METHODS

The extent of selective EEG synchronization in the alpha range has been taken as a measure of cortical inhibition. EEG was registered in 60 infants aged 8-11 months during: (1) attention to an object in the visual field (externally controlled attention); (2) anticipation of the person in the peek-a-boo game (internally controlled attention).

RESULTS

The infants who demonstrated longer periods of anticipatory attention had higher absolute spectral amplitude in the broad frequency range under both experimental conditions. It was suggested that the effect of 'overall' EEG synchronization is related to some stable individual differences in psychophysiological traits. To control for the effect of overall EEG synchronization the relation between relative alpha amplitudes in 6.4-10 Hz range and the duration of internally controlled attention was analyzed. The infants with longer compared to shorter anticipatory attention spans had relatively higher 6.8 Hz alpha synchronization at posterior parietal sites under this experimental condition.

CONCLUSIONS

It was suggested that alpha synchronization over posterior parietal cortex reflects an active inhibition of certain parietal networks involved in maintaining attention to peripheral visual field rather than merely an 'idle' state of this cortical area. Such an inhibition appears to allow infants to avoid interference of concurrent visual stimulation at the periphery of the visual field.

Increased frontal phase-locking of event-related alpha oscillations during task processing

Recent findings substantiate the view that electroencephalographic (EEG) alpha rhythm (7-13 Hz) is functionally involved in cognitive stimulus processing. Our previous results have shown that enhanced alpha responses to auditory task stimuli can be well synchronized with stimulus until 800-1000 ms. The present study analyzed the effect of perceptual uncertainty and difficulty in decision making on event-related alpha oscillations in single auditory event-related brain potentials (ERPs). EEG was recorded from Fz, Cz and Pz electrodes in 10 subjects participating in two experimental sessions, in which auditory stimuli with equal physical parameters were presented under passive and task instructions. Separate measurements of single alpha response amplitude and phase-locking were performed and statistically analyzed for consecutive time windows in the post-stimulus epoch. Major results show that, during the cognitive task, the phase-locking of alpha oscillations at the frontal site is significantly increased in the time window of 500-1000 ms after stimulation. Thus, the involvement of enhanced and synchronized frontal alpha activity in higher brain processes is strongly emphasized.

The effectiveness of activating electrical devices using alpha wave synchronisation contingent with eye closure

Increases in alpha wave amplitude occur with eye closure (EC) and decreases occur when the eyes are opened (EO). The research reports in this paper emphasise effectiveness of people using these alpha wave changes to activate electrical devices. Effectiveness was measured in terms of time taken and errors made when selecting the correct device. Ten non-disabled subjects significantly decreased the time taken and errors made to activate correctly a device using a six-option environmental control system (ECS) in the laboratory. In addition, a severely disabled person was shown to use the ECS successfully to control her television in her home environment. This research demonstrates that alpha wave manipulation contingent with EC and EO can be the basis for a reliable and quick switching system for controlling electrical devices. Applications to disability are discussed.

Operant conditioning of left-hemispheric slow cortical potentials and its effect on word processing

This study investigated whether language-related cognitive processes can be modified by learned modulation of cortical activity. Study participants received feedback of slow cortical potentials (SCPs) recorded above left-hemispheric language cortices and were reinforced for producing negative and positive shifts upon two different discriminative stimuli. In all subjects who achieved reliable control of left-hemispheric brain responses, substantial modification of word processing was observed. Behavioral modification could be documented in two experiments in which word probes were presented following discriminative stimuli. When negative shifts of the EEG were required, lexical decisions on words were substantially speeded, while they were slowed during positivity conditions. There was no indication for any performance difference between conditions in control subjects who failed to achieve control over SCPs after feedback training. This result was replicated in an experiment using lateralized-tachistoscopic stimulus presentation. Comparisons of word and pseudoword responses in both experiments indicated that behavioral modification was most pronounced for word responses. It was also not seen in a simple reaction time task not involving language materials. This argues against a global effect related to perception, visuo-spatial attention, or motor processes. We conclude that linguistic processes can be influenced by modification of cortical activity due to operant conditioning. In closing, tentative explanations of the present results based on theories of language and attention processes are being discussed.

Event-related alpha oscillations in task processing

OBJECTIVES

Recent findings substantiate the view that electroencephalographic (EEG) alpha rhythm (7-13 Hz) is functionally involved in information processing. However, the association of alpha rhythms with cognitive brain processes is less well understood because both augmentation and suppression of alpha oscillations have been observed to accompany task performance. The present study evaluates the effect of task processing on event-related alpha oscillations at the level of single-sweep analysis.

METHODS

EEG was recorded from Fz, Cz and Pz electrodes in 10 subjects participating in two experimental sessions, in which auditory stimuli with equal physical parameters were presented under different instructions (passive and task). Separate measurements of single-sweep amplitude and phase-locking were performed and statistically analyzed for consecutive time windows in the poststimulus epoch.

RESULTS

Major results show that, during the cognitive task, the phase-locking of alpha oscillations at the frontal site is significantly increased for the time window of 500-1000 ms after stimulation.

CONCLUSIONS

The involvement of enhanced and synchronized frontal alpha activity in higher brain processes is strongly emphasized.

Enhancement of left-right sensorimotor EEG differences during feedback-regulated motor imagery

EEG feedback studies demonstrate that human subjects can learn to regulate electrocortical activity over the sensorimotor cortex. Such self-induced EEG changes could serve as control signals for a Brain Computer Interface. The experimental task of the current study was to imagine either right-hand or left-hand movement depending on a visual cue stimulus on a computer monitor. The performance of this imagination task was controlled on-line by means of a feedback bar that represented the current EEG pattern. EEG signals recorded from left and right central recording sites were used for on-line classification. For the estimation of EEG parameters, an adaptive autoregressive model was applied, and a linear discriminant classifier was used to discriminate between EEG patterns associated with left and right motor imagery. Four trained subjects reached 85% to 95% classification accuracy in the course of the experimental sessions. To investigate the impact of continuous feedback presentation, time courses of band power changes were computed for subject-specific frequency bands. The EEG data revealed a significant event-related desynchronization over the contralateral central area in all subjects. Two subjects simultaneously displayed synchronization of EEG activity (event-related synchronization) over the ipsilateral side. During feedback presentation the event-related desynchronization/event-related synchronization patterns showed increased hemispheric asymmetry compared to initial control sessions without feedback.

EEG alpha rhythm in infants

The 'functional topography' approach has been applied to study alpha rhythms in infant twins during the second half-year of life. The experimental sample included 154 normal infants born at 32-41 weeks of gestational age. Their chronological age varied from 7.4 to 12.4 months. EEG was registered during wakefulness under two experimental conditions: sustained visual attention and dark homogenous visual field. During darkness as compared with visual attention the sharp increase of spectral amplitudes within 5.2-9.6 Hz band was observed over the occipital-parietal cortex. The properties of the 5.2-9.6 Hz occipital rhythmic activity comply with the classical properties of alpha rhythm. The distinct spectral peak in 6.0-8.8 Hz band at precentral recording sites was observed during sustained visual attention. This rhythmic component was suppressed under the condition of total darkness. Arguments in favour of homology between the infant central rhythm and adult sensorimotor mu rhythm are advanced. The group mean of alpha peak frequency increased from 6.24 +/- 0.45 Hz at 8 months to 6.78 +/- 0.38 Hz at 11 months of chronological age. The frequency of infant alpha rhythm depended only on the period of extrauterine experience, regardless of gestational age at birth. This result points to the critical role of early visual experience in alpha rhythm development. The group mean of the peak frequency of mu rhythm also increased during the second half-year of life, from 7.03 +/- 0.47 Hz at 8 months to 7.42 +/- 0.46 Hz at 11 months. Unlike alpha rhythm, the peak frequency of mu rhythm depended on duration of both intra- and extrauterine development. We speculate that the development of sensorimotor mu rhythm is influenced by somatosensory stimulation, which, in sharp contrast to the visual input, is present in the uterus.

[Event-related desynchronization and synchronization. Reactivity of electrocortical rhythms in relation to the planning and execution of voluntary movement]

Cortical electroencephalographic rhythms reactivity may be quantified using event-related desynchronization (ERD) and synchronization (ERS) methods. We therefore studied cortical activation occurring during programming and performance of voluntary movement in healthy subjects. EEG power evolution within the reactive frequency bands (mu and beta central rhythms) was averaged before, during and after a minimum of 50 self-paced flexions of the thumb. Recordings in 18 normal adults showed that ERD (decrease in power) of mu rhythm started 2,000 ms before movement onset, while ERD of beta rhythm started 1,500 ms before movement onset. Early ERD of mu and beta rhythms were located over the contralateral central region covering primary motor cortex. They were followed by bilateral ERD occurring over ipsilateral and contralateral central regions during performance of the movement. At the end of the movement, an ERS (increase in power) of beta rhythm occurred. These results suggest that programming of voluntary movement induces early activation in contralateral sensorimotor areas, while performance of the movement induces bilateral activation in sensorimotor areas. ERS of beta rhythm occurring at the end of the movement could correspond to inactivation of motor areas activated by movement. Based on EEG activity, ERD and ERS prove to be useful methods to analyze cortical activation during programming and performance of voluntary movements with good spatial and temporal resolution.

Responses of the nervous system to low frequency stimulation and EEG rhythms: clinical implications

The present paper reviews literature data on the role of the non-specific central nervous system response mechanisms on the therapeutic effects of relatively weak external stimulations used in clinical practice. The factors affecting the stimulation efficiency and increased sensitiveness of living things to extra-low-frequency periodic stimulations (in the range of from less than 1 Hz to tens of Hz) are discussed. Among the factors determining such effects, the non-specific response mechanisms of the nervous system, the resonance phenomena in different organism systems, and the interaction of external stimulation with endogenous rhythmic processes are analyzed. Most attention is given to endogenous rhythms of the electrical brain activity reflected in the EEG rhythms. A high resolution EEG processing approach that is used to reveal the intrinsic oscillators in the individual EEG spectrum is described. Synchronization of sensory stimulation parameters with the frequencies of intrinsic EEG oscillators is supposed to be an appropriate way to enhance the therapeutic effects of various sensory stimulation treatments. Specific methods for utilizing resonance therapy via sensory stimulation with intrinsic EEG frequencies, and for automatic modulation of stimulation parameters by endogenous organism rhythms are delineated; some preliminary results are described.

Evoked EEG alpha oscillations in the cat brain--a correlate of primary sensory processing?

Event-related alpha (10 Hz) oscillations in the EEG were measured in cats by means of intracranial electrodes. Simultaneous recordings were made from auditory and visual cortex while auditory and visual stimuli were applied (in separate sessions). Frequency domain analysis of the EEG responses showed marked alpha components only for adequate stimulation (e.g. visual cortex-visual stimulus). This hints at a functional relationship between alpha responses and primary sensory processing.

Relative alpha desynchronization and synchronization during speech perception

Brain processes elicited by speech were studied in 10 right-handed subjects by means of examining the desynchronization and synchronization of the 8-10 Hz and 10-12 Hz EEG alpha frequency bands. The subjects listened to an auditorily presented 5 min text passage. The text was presented both forward and backward. Listening to the text forward elicited alpha desynchronization in both of the frequency bands studied, whereas listening to the same text presented backward elicited synchronization in the 10-12 Hz frequency band only. Listening to the text forward elicited greater desynchronization than listening to the text backward. In the 10-12 Hz frequency band, listening to the text forward elicited desynchronization whereas listening to the same text backward elicited synchronization. This dissociation was not observed in the 8-10 Hz frequency band. The results suggest that the lower and upper alpha bands differ such that the 10-12 Hz frequency band exhibits reactivity to the presence of linguistic content while the 8-10 Hz band shows an unspecific response.

On the existence of different types of central beta rhythms below 30 Hz

EEGs were recorded from sensorimotor areas of 12 subjects performing unilateral self-paced brisk and slow finger movements. Two different beta components were found below 30 Hz: (i) One component, at about twice the frequency of the mu rhythm, showed desynchronization in parallel with the mu rhythm starting at about 2 s prior to movement. Measurements of bicoherence have shown that this beta component can be non-linearly related to the arch-shaped mu rhythm. (ii) Another beta component started to desynchronize about 1 s prior to movement, recovered very fast and displayed a pronounced post-movement beta synchronization (PMBS) within the first second after movement-offset. This PMBS was found in the frequency band between 12 and 26 Hz. The average percentage power increase at contralateral sensorimotor area was 232% (SD = 82%) for brisk and 265% (SD = 102%) for slow movements. The PMBS was of contralateral dominance and is interpreted as a correlate of active inhibition or idling of the primary motor area following movement execution.

Some recent applications of clinical psychophysiology

In this paper, major trends in the recent applications of Clinical Psychophysiology are summarized. These clinical applications pertain to neurosurgical interventions, and to neurological, psychiatric, pediatric, and ophthalmological diseases. Other applications of Clinical Psychophysiology include psychosomatic diseases such as cardiovascular, gastrointestinal, respiratory and sleep-related disorders. The International Organization of Psychophysiology based on its Constitution and By-Laws (IOP, 1981, 1982) is promoting high scientific standards in the applications of Clinical Psychophysiology to various medical conditions.

Intention as a component of the alpha-rhythm response to mental activity

Many studies of alpha-rhythm reactivity conclude that alpha is selectively attenuated by attention accompanying mental activity. The topography of this attenuation is assumed to match the relevant functional topography of the cortex. But there are reports of apparent increased attention resulting in no change, or even enhanced alpha - the paradoxical response. It is proposed that in this case, alpha amplitude may be dependent on an intention component of behaviour. Some conflicting reports of alpha reactivity to mental processes may then be resolved. It is argued that the classical attention model of alpha is untenable, except for simple sensori-motor responses. Reasons are given to support this and the concept of intention as a neuropsychological variable is introduced. Evidence is presented for a generalisation of an oculomotor model of alpha activity proposed by Wertheim who demonstrated that alpha reduces during attentive, but not during intentive visual behaviour. The generalisation follows from reports of enhanced alpha in the few seconds prior to a skilled action in sport, and by neurophysiological evidence for a separate cortical organisation for perception and action. Varying proportions of attention and intention then add a dimension to the factors influencing alpha blocking which may explain its inconsistent response.

On-line EEG classification during externally-paced hand movements using a neural network-based classifier

EEGs of 6 normal subjects were recorded during sequences of periodic left or right hand movement. Left or right was indicated by a visual cue. The question posed was: 'Is it possible to move a cursor on a monitor to the right or left side using the EEG signals for cursor control?' For this purpose the EEG during performance of hand movement was analyzed and classified on-line. A neural network in form of a learning vector quantizertion (LVQ) with an input dimension of 16 was trained to classify EEG patterns from two electrodes and two time windows. After two training sessions on 2 different days, 4 subjects showed a classification accuracy of 89-100%. For two subjects classification was not possible. These results show that in general movement specific EEG-patterns can be found, classified in real time and used to move a cursor on a monitor to the left or right. On-line EEG classification is necessary when the EEG is used as input signal to a brain computer interface (BCI). Such a BCI can be a help for handicapped people.

Event-related synchronization (ERS) in the alpha band--an electrophysiological correlate of cortical idling: a review

EEG desynchronization is a reliable correlate of excited neural structures of activated cortical areas. EEG synchronization within the alpha band may be an electrophysiological correlate of deactivated cortical areas. Such areas are not processing sensory information or motor output and can be considered to be in an idling state. One example of such an idling cortical area is the enhancement of mu rhythms in the primary hand area during visual processing or during foot movement. In both circumstances, the neurons in the hand area are not needed for visual processing or preparation for foot movement. As a result of this, an enhanced hand area mu rhythm can be observed.

Event-related desynchronisation of central beta-rhythms during brisk and slow self-paced finger movements of dominant and nondominant hand

Changes in central beta-rhythms (14-29 Hz) during movement were investigated in 12 right-handed subjects by quantifying event-related desynchronisation (ERD). EEG was recorded from 24 closely spaced electrodes overlaying the left and right sensorimotor hand area. The subjects performed approximately 80 brisk (movement time < 0.21 s) and 80 slow (movement time 1.3-2.1 s) self-paced extensions of their left or right index finger. Beta-band power attenuation in the preparatory period (2.0-0.5 s before movement onset) was larger in the contralateral hemisphere in both types of movement and similar for both fingers. In the 0.4-s period before the onset of extensor muscle contraction, right-finger movements only showed a significant contralateral preponderance of beta-ERD. During movement an anterior ERD predominance in the right sensorimotor hand area and a widespread ERD in the left sensorimotor area was found for both fingers. The recovery and rebound of beta-rhythms showed contralateral preponderance which was expressed more in the right hemisphere, especially after left-finger movements. The results suggest that the dynamics of premovement desynchronisation and postmovement synchronisation of central beta-rhythms is related to hand dominance.

Post-movement beta synchronization. A correlate of an idling motor area?

Post-movement beta (around 20 Hz) synchronization was investigated in 2 experiments with self-paced finger extension and flexion and externally paced wrist movement. The electrodes were fixed over the sensorimotor area in distances of 2.5 cm. It was found that after a brisk finger movement the desynchronized beta rhythm displayed a fast recovery and a short-lasting synchronization within 1 sec. This post-movement beta synchronization was maximal over the contralateral hemisphere and localized slightly more anterior to the maximal desynchronization of the hand area mu rhythm. The post-movement beta synchronization is interpreted as a correlate of "idling" motor cortex neurons.