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.     

Cortical involvement in the sensory and motor symptoms of primary restless legs syndrome

BackgroundRestless legs syndrome (RLS) is characterized by closely interrelated motor and sensory disorders. Two types of involuntary movement can be observed: periodic leg movements during wakefulness (PLMW) and periodic leg movements during sleep (PLMS). Basal ganglia dysfunction in primary RLS has often been suggested. However, clinical observations raise the hypothesis of sensorimotor cortical involvement in RLS symptoms. Here, we explored cortical function via movement-related beta and mu rhythm reactivity.MethodsTwelve patients with idiopathic, primary RLS were investigated and compared with 10 healthy subjects. In the patient group, we analyzed event-related beta and mu (de)synchronization (ERD/S) for PLMS and PLMW during a suggested immobilization test (SIT). An ERD/S analysis was also performed in patients and controls during self-paced right ankle dorsal flexion at 8:30 PM (i.e., the symptomatic period for patients) and 8:30 AM (the asymptomatic period).ResultsBefore PLMS, there was no ERD. Intense ERS was recorded after PLMS. As with voluntary movement, cortical ERD was always observed before PLMW. After PLMW, ERS had a diffuse scalp distribution. Furthermore, the ERS and ERD amplitudes and durations for voluntary movement were greater during the symptomatic period than during the asymptomatic period and in comparison with healthy controls, who presented an evening decrease in these parameters. Patients and controls had similar ERD and ERS patterns in the morning.ConclusionOn the basis of a rhythm reactivity study, we conclude that the symptoms of RLS are related to cortical sensorimotor dysfunction.     

Event-related beta EEG-changes during passive and attempted foot movements in paraplegic patients

A number of electroencephalographic (EEG) studies report on motor event-related desynchronization and synchronization (ERD/ERS) in the beta band, i.e. a decrease and increase of spectral amplitudes of central beta rhythms in the range from 13 to 35 Hz. Following an ERD that occurs shortly before and during the movement, bursts of beta oscillations (beta ERS) appear within a 1-s interval after movement offset. Such a post-movement beta ERS has been reported after voluntary hand movements, passive movements, movement imagination, and also after movements induced by functional electrical stimulation. The present study compares ERD/ERS patterns in paraplegic patients (suffering from a complete spinal cord injury) and healthy subjects during attempted (active) and passive foot movements. The aim of this work is to address the question, whether patients do have the same focal beta ERD/ERS pattern during attempted foot movement as healthy subjects do. The results showed midcentral-focused beta ERD/ERS patterns during passive, active, and imagined foot movements in healthy subjects. This is in contrast to a diffuse and broad distributed ERD/ERS pattern during attempted foot movements in patients. Only one patient showed a similar ERD/ERS pattern. Furthermore, no significant ERD/ERS patterns during passive foot movement in the group of the paraplegics could be found.     

Decreased movement-related beta desynchronization and impaired post-movement beta rebound in amyotrophic lateral sclerosis

ObjectiveThis study explored event-related desynchronization (ERD) and synchronization (ERS) in amyotrophic lateral sclerosis (ALS) to quantify cortical sensorimotor processes during volitional movements. We furthermore compared ERD/ERS measures with clinical scores and movement-related cortical potential (MRCP) amplitudes.MethodsElectroencephalograms were recorded while 21 ALS patients and 19 controls performed two self-paced motor tasks: sniffing and right index finger flexion. Based on Wavelet analysis the alpha and beta frequency bands were selected for subsequent evaluation.ResultsPatients generated significantly smaller resting alpha spectral power density (SPD) and smaller beta ERD compared to controls. Additionally patients exhibited merely unilateral post-movement ERS (beta rebound) whereas this phenomenon was bilateral in controls. ERD/ERS amplitudes did not correlate with corresponding MRCPs for either patients or controls.ConclusionsThe smaller resting alpha SPD and beta ERD and asymmetrical appearance of beta ERS in patients compared to controls could be the result of pyramidal cell degeneration and/or corpus callosum involvement in ALS.SignificanceThese results support the notion of reduced movement preparation in ALS involving also areas outside the motor cortex. Furthermore post-movement cortical inhibition seems to be impaired in ALS. ERD/ERS and MRCP are found to be independent measures of cortical motor functions in ALS.     

Voluntary tic suppression and the normalization of motor cortical beta power in Gilles de la Tourette syndrome: an EEG study

Gilles de la Tourette syndrome (GTS) is a neurological condition characterized by motor and vocal tics. Previous studies suggested that this syndrome is associated with abnormal sensorimotor cortex activity at rest, as well as during the execution of voluntary movements. It has been hypothesized that this abnormality might be interpreted as a form of increased tonic inhibition, probably to suppress tics; however, this hypothesis has not been tested so far. The present study was designed to formally test how voluntary tic suppression in GTS influences the activity of the sensorimotor cortex during the execution of a motor task. We used EEG to record neural activity over the contralateral sensorimotor cortex during a finger movement task in adult GTS patients, in both free ticcing and tic suppression conditions; these data were then compared with those collected during the same task in age‐matched healthy subjects. We focused on the levels of activity in the beta frequency band, which is typically associated with the activation of the motor system, during three different phases: a pre‐movement, a movement, and a post‐movement phase. GTS patients showed decreased levels of beta modulation with respect to the healthy controls, during the execution of the task; however, this abnormal pattern returned to be normal when they were explicitly asked to suppress their tics while moving. This is the first demonstration that voluntary tic suppression in GTS operates through the normalization of the EEG rhythm in the beta frequency range during the execution of a voluntary finger movement.     

Event-related desynchronization and excitability of the ipsilateral motor cortex during simple self-paced finger movements.

OBJECTIVE: To study the time course of oscillatory EEG activity and corticospinal excitability of the ipsilateral primary motor cortex (iM1) during self-paced phasic extension movements of fingers II-V. METHODS: We designed an experiment in which cortical activation, measured by spectral-power analysis of 28-channel EEG, and cortical excitability, measured by transcranial magnetic stimulation (TMS), were assessed during phasic self-paced extensions of the right fingers II-V in 28 right-handed subjects. TMS was delivered to iM1 0-1500 ms after movement onset. RESULTS: Ipsilateral event-related desynchronization (ERD) during finger movement was paralleled by increased cortical excitability of iM1 from 0-200 ms after movement onset and by increased intracortical facilitation (ICF) without changes in intracortical inhibition (ICI) or peripheral measures (F waves). TMS during periods of post-movement event-related synchronization (ERS) revealed no significant changes in cortical excitability in iM1. CONCLUSIONS: Our findings indicate that motor cortical ERD ipsilateral to the movement is associated with increased corticospinal excitability, while ERS is coupled with its removal. These data are compatible with the concept that iM1 contributes actively to motor control. No evidence for inhibitory modulation of iM1 was detected in association with self-paced phasic finger movements. SIGNIFICANCE: Understanding the physiological role of iM1 in motor control.     

Event-related desynchronization in reaction time paradigms: a comparison with event-related potentials and corticospinal excitability.

OBJECTIVES: To study cortical activity in different motor tasks, we compared event-related desynchronization (ERD) and event-related potentials (ERPs) in different reaction time (RT) paradigms with the time course of corticospinal excitability. METHODS: Nine right-handed, normal subjects performed right or left thumb extensions in simple, choice and go/no go auditory RT paradigms. Eight subjects had participated in a previous study evaluating changes in corticospinal excitability during the same paradigms. Twenty-nine EEG channels with electrooculogram and bilateral EMG monitoring were collected. ERPs and ERD of 10 and 18-22 Hz bands were obtained with respect to tone administration and EMG onset. RESULTS: Trials with movement showed lateralized ERP components, corresponding to the motor potential (MP), both in the averages on the tone and on EMG. The MP corresponded well in time and location to the rise in corticospinal excitability on the moving side observed in the previous study. Sensorimotor ERD, followed by event-related synchronization (ERS), was present for trials with movements and for the no go. ERD was present contralaterally during movement preparation and in no go trials, while it was bilateral during motor execution. No go ERD was followed more rapidly by ERS than in trials with movement. This finding suggests that in no go trials, there is a brief active process in the sensorimotor areas. ERD and ERS do not correspond, respectively, in time and location to increases and decreases in corticospinal excitability. In fact, ERD is bilateral during movement execution, when corticospinal inhibition of the side at rest is observed. Contralateral no go ERS occurs later than corticospinal inhibition, which is bilateral. CONCLUSIONS: These findings may suggest that ERD is compatible with both corticospinal activation and inhibition, ERS indicating the removal of either, resulting in cortical idling.     

Motor event-related synchronization as an inhibitory biomarker of pain severity,sensitivity, and chronicity in patients with knee osteoarthritis

ObjectiveThe study aimed to examine the clinical and neurophysiological predictors of motor event-related desynchronization (ERD) and synchronization (ERS) in patients with chronic pain due to knee osteoarthritis (KOA).MethodsWe performed a cross-sectional analysis of our cohort study (DEFINE cohort), KOA arm, with 71 patients, including demographic, functionality, genetic and neurophysiological measures. ERD/ERS was evaluated during hand motor tasks (motor execution, active and passive observation, and imagery). Multivariate regression models were used to explore predictors of ERD/ERS.ResultsAlthough we found an altered ERD/ERS pattern during motor execution and active observation, the ERS pattern could only be clearly differentiated after passive observation.`. We found no predictors of ERD (excitatory biomarker). For ERS (inhibitory biomarker), our results showed that the main predictors differ across EEG frequency bands. Considering pain measures, we found that visual analogue scale (VAS, right knee) and chronicity of pain negatively predict low beta and high beta ERS, respectively. Pain threshold was positively correlated with alpha ERS, while 36-Item Short Form Survey (SF-36) emotional domain positively predicted beta ERS. Regarding transcranial magnetic stimulation (TMS) markers, intracortical inhibition (ICF) negatively predicted beta and low beta ERS, and left hemisphere cortical silent period (CSP) negatively predicted low beta ERS.ConclusionConsidering that higher power of ERS indicates a stronger cortical organization and inhibitory drive, our results show that limitation of activities due to emotional factors, lower pain threshold, higher VAS pain, and longer duration of pain are associated with lower ERS power (in alpha and beta frequencies), thus indicating a lower inhibitory drive. In the same direction, a lower inhibitory drive as indicated by higher ERS power is associated with higher ICF amplitude. Although there was a negative association between ERS and CSP, this may indicate that ICF values are adjusting CSP results. Our findings support the idea that a less organized cortical response as indicated by changes to the ERS is associated with higher pain correlates in subjects with KOA.     

Cortical activation to voluntary movement in amyotrophic lateral sclerosis is related to corticospinal damage: electrophysiological evidence

ObjectivesThe time course of mu and beta sensorimotor rhythms, with event-related desynchronisation (ERD) to preparation and execution of voluntary movement followed by synchronisation (ERS) after movement, is considered to indicate cortical activation and idling, respectively. We investigated ERD and ERS in amyotrophic lateral sclerosis (ALS) patients and the relationship with anatomical and neurophysiological measures of corticospinal tract damage.MethodsPre-movement mu and beta ERD, and post-movement beta ERS were analysed in 16 ALS patients and 15 healthy controls performing self-paced brisk right thumb extensions. Apparent diffusion coefficient (ADC) of corticospinal tract was measured with magnetic resonance imaging (MRI). Motor-evoked potentials (MEPs) to the right abductor pollicis brevis were obtained using transcranial magnetic stimulation (TMS).ResultsMovement-related electromyographic activity was similar in the two groups. Post-movement ERS was significantly reduced in ALS group and negatively correlated with the amount of corticospinal damage as from MRI and TMS measures. ERD did not significantly differ between groups.ConclusionsAlterations of cortical activity in ALS patients were limited to the post-movement phase, as indicated by reduced ERS, and could be linked to reduced cortical inhibition rather than to generalised hyperexcitability.SignificanceThe correlation between ERS and corticospinal damage severity might be interpreted as a functional compensation or dysfunction of inhibitory systems paralleling corticospinal damage.     

Dynamics of movement‐related cortical potentials and sensorimotor oscillations during palmar grasp movements

Movement‐related cortical potentials (MRCP) and sensorimotor oscillatory electroencephalographic (EEG) activity (event‐related desynchronization/synchronization—ERD/ERS) provide complementary information of the associated motor activity. The aim of this study was to provide comparative spatio‐temporal analysis of both EEG phenomena associated with palmar grasping motions including hand opening and closing phases. Nine healthy participants were instructed to perform self‐paced, right hand grasping movements. EEG was recorded from 28 sites synchronous with electromyography (EMG) of wrist/fingers extensors and flexors. Statistical analysis of the EEG data revealed significant differences (p < .05) between the idle state (baseline) and motor preparation/execution periods in majority of recorded channels. The earliest statistical significance in MRCPs was observed for channel FC3 at ?460.9 ms, while the earliest significant ERD was observed at 164.1 ms for channel C3. MRCP and ERD/ERS topographies in our study are in line with the results of previous studies comparing MRCP and ERD/ERS spatio‐temporal patterns during upper limb movements, however, results of our study show that MRCP significant differences compared to the baseline appear in most channels earlier than ERD (on average 613.6 ± 191.5 ms earlier). This implies an advantage of MRCP signals for grasping movements' prediction, which is in contrast to previous reports. Moreover, combined spatio‐temporal information on MRCP and ERD/ERS presented in this paper may serve for future optimization of grasp movement prediction/detection hybrid algorithms in the context of restorative brain–computer interface technology.     

Changes in oscillatory cortical activity related to a visuomotor task in young and elderly healthy subjects.

OBJECTIVE: In order to better understand the spatio-temporal interaction of the activated cortical areas when the movement is visuo-guided and to assess the age effect on the spatio-temporal pattern of cortical activity, we have compared a proximo-distal movement with visual-motor control and hand-eye coordination (targeting movement) with a distal and a proximal movement. METHODS: Brain's electrical activity was studied using the analysis of event-related (de)synchronizations (ERD/S) of cortical mu and beta rhythms in 17 subjects, 8 young and 9 elderly subjects. RESULTS: In both populations, we found an earlier and broader mu and beta ERD during the preparation of the targeting movement compared to distal and proximal movements, principally involving the contralateral parietal region. During the execution, a spreading over the parietocentral region during proximal movement and over the parietal region during targeting movement was observed. After the execution of proximal and targeting movements, a wider and higher beta ERS was observed only in the young subjects. In the elderly subjects, our results showed a significant decrease of beta ERS during the targeting task. CONCLUSIONS: These results suggest there was a larger recruitment of cortical areas, involving notably the parietal cortex when the movement is visuo-guided. Moreover, cerebral aging-related changes in the spatio-temporal beta ERS pattern suggests an impaired sensory integration.     

Event-related desynchronization and Parkinson disease. Importance in the analysis of the phase of preparation for movement]

This study was aimed at determining the spatiotemporal distribution of event-related desynchronization (ERD) during self-paced voluntary movement in order to establish the interest of this method for the analysis of movement programming in Parkinson's disease. Desynchronization of mu rhythm was recorded 2 s before to 0.5 s after right then left self-paced voluntary wrist flexions from 11 leads covering the primary sensorimotor cortex (central), supplementary motor area (frontocentral) and parietal cortex (parietocentral). Recordings were obtained from ten control subjects, ten patients treated for Parkinson's disease (bilateral symptoms) and 20 patients presenting with right or left hemiparkinsonism before and after chronic administration of L-dopa. In the control group, ERD started over the contralateral primary sensorimotor cortex 1,750 ms before movement and was bilateral just before performance of the movement. In both treated and de novo Parkinson's disease groups, decrease in ERD latency (1,000 to 1,250 ms before movement) was only observed when movements were performed with the akinetic hand and corresponded to a decrease in motor cortical activity. This confirmed that programming of movement is affected in Parkinson's disease. Earlier ERD with central ipsilateral distribution were also observed, suggesting that other cortical areas might be activated to compensate for dysfunction of movement programming and to increase the level of cortical activity required for performance of the movement. The administration of L-dopa to de novo hemiparkinsonians patients resulted in increased ERD latency over contralateral and ipsilateral central areas. As in the treated Parkinson's disease group, frontocentral ERD could also be recorded. L-dopa would thus partially restore the affected motor programmation and modulate cortical activation in both supplementary motor area and primary motor cortex, the later receiving more afferences from basal ganglia.     

Motor preparation is more impaired in Parkinson's disease when sensorimotor integration is involved

Objective: This study aimed to investigate changes in spatio-temporal, event-related (de)synchronization (ERD/ERS) patterns recorded with respect to the more akinetic versus the less akinetic side during performance of a visuo-guided targeting movement when compared to an index finger extension.Methods: Twelve de novo parkinsonian patients were recorded. ERD/ERS in mu and beta frequency bands was computed from 21 source derivations.Results: When the index finger extension was performed with the less akinetic limb, mu ERD focused over contralateral central region appeared 2 s before movement. With the targeting movement, additional pre-movement mu ERD was observed over the parietal region, as well as earlier ipsilateral mu ERD. When the same movements were performed with the more akinetic limb, we observed delayed mu ERD over contralateral regions, earlier ipsilateral mu ERD and a lack of contralateral parietal mu ERD before the targeting movement. Following index finger extension for the less akinetic limb, a focused contralateral central beta ERS was recorded, increasing and spreading after the targeting movement. In contrast, for the more akinetic limb, beta ERS was dramatically attenuated and remained unchanged after the targeting movement.Conclusions: These results confirm the fact that motor programming is delayed, and provide some insight into what may well be impaired sensorimotor integration in Parkinson's disease.     

Abnormal Cortical Activation During Planning of Voluntary Movement in Patients with Epilepsy with Focal Motor Seizures: Event-Related Desynchronization Study of Electroencephalographic mu Rhythm

Summary: Purpose: The spatiotemporal distribution of EEG mu rhythm desynchronization was analyzed in patients with partial epilepsy to determine whether frequent focal motor seizures could induce a change of cortical activation during the planning of a voluntary movement.
Methods: The event-related desynchronization (ERD) of the mu rhythm was quantified during a self-paced voluntary movement of the thumb. The results were compared betyeen two groups of patients with epilepsy: in one group (n = 12), the patients had frontal lobe epilepsy with frequent focal motor seizures (FMS); in the second group (n = 12), they had temporal lobe epilepsy (TLE) with complex partial seizures but no ictal movement disorder. The results were also compared with those of control subjects of same age (n = 10).
Results: In the control group, desynchronization of murhythm began over the contralateral central region 2,000 ms before the movement onset. In the FMS group, the desynchronization of mu rhythm was delayed, appearing only 500 ms before the movement onset, and the amplitude of ERD was increased over the frontocentral region. In the TLE group, the spatiotemporal pattern of ERD was the same as in normal subjects, but the amplitude of ERD was increased.
Conclusions: These results indicate that there is a change of reactivity of mu rhythm in patients with partial epilepsy. The change in spatiotemporal pattern of ERD in patients with frequent focal motor seizures suggests that there is an abnormal cortical activation during the planning of a voluntary movement.     

Cue-induced beta rebound during withholding of overt and covert foot movement

ObjectiveBeta rebound is the term for bursts of EEG activity in the beta band observable after movement or somatosensory stimulation. It is assumed to reflect an active inhibition process. Our aim was to investigate the differences in the beta rebound between movement termination and withholding of movement, and the withholding of overt and covert movement.MethodsTwenty healthy persons completed Go/NoGo experiments with real and imaginary foot movements (dorsiflexion of both feet). Only participants that presented a beta rebound were considered. Event-related (de)synchronization provided the time course of the beta rebound from a participant specific frequency band. Statistical analyses revealed the significant differences between pairs of conditions: motor execution Go vs. motor execution NoGo, and motor execution NoGo vs. motor imagery NoGo.ResultsThe beta rebound is stronger and lasts longer after termination of movement than during withholding of a motor response (9 participants). Withholding of overt movement generates a stronger, longer, and more widespread beta rebound than the withholding of imaginary movement (7 participants). The beta rebound is more common after termination (16/16) and withholding of real movement (12/16) than during withholding of imaginary movements (7/16).ConclusionsThese phenomena share a common origin and a common frequency band. Their functional meaning is assumed to be the same, although there are differences in time span and intensity of the beta ERS.SignificanceFirst direct comparison of the beta rebound between motor execution and motor withholding, as well as withholding of overt and covert foot movement. A beta rebound also occurs during withholding of a motor task, and it is more common and strong for overt movement than for covert movement.     

Basic mechanisms of central rhythms reactivity to preparation and execution of a voluntary movement: a stereoelectroencephalographic study.

OBJECTIVE: To localize the sources of mu, beta and gamma rhythms and to explore the functional significance of their reactivity. METHODS: We used the method of quantification of event-related desynchronization (ERD) and synchronization (ERS) to analyze the reactivity of intracerebral rhythms recorded in stereoelectroencephalography within the sensorimotor areas during the preparation and the execution of a simple self-paced hand movement. We recorded 3 epileptic subjects who were explored before a surgical treatment. RESULTS: An ERD of mu and beta rhythms has been recorded before the movement onset in the precentral gyrus, spreading then to the postcentral gyrus and to the frontal medial cortex. The frontal lateral cortex was inconstantly involved during the movement. The movement offset was followed by an important and focused beta ERS which was found within the pre- and post-central gyrus and the frontal medial cortex. Within the beta band, we observed several narrower bands with different reactivities and locations. Focused gamma reactivity was also found in the precentral and postcentral gyri. CONCLUSIONS: The reactivities of mu and beta rhythms are different but their locations overlap. Mu ERD is a diffuse phenomenon that reflects the activation of all the sensorimotor areas during a simple movement. Beta band is likely to be composed of different rhythms with different functional significance. The primary motor area seems to contain two distinct areas with different reactivity to the movement preparation and execution.     

Abnormal cortical mechanisms in voluntary muscle relaxation in de novo parkinsonian patients.

This study aimed at elucidating how the cortical mechanism underlying the preparation and the postmovement phase of voluntary hand muscle relaxation is affected in Parkinson's disease. Event-related mu and beta (de)synchronization (ERD/S) related to voluntary muscle contraction and relaxation were recorded in 16 untreated, akineto-rigid, predominantly hemiparkinsonian patients. The results were compared with data from 10 age-matched, healthy subjects. In the muscle relaxation task, the subject held the wrist in an extended position and then let the hand drop by voluntarily relaxing wrist extensor contraction, i.e., without any overt, associated muscle contraction. In the muscle contraction task, subjects performed a self-initiated brief wrist extension. A same pattern of ERD/S was observed in control subjects and parkinsonian patients performing the motor tasks with their less affected limb. In contrast, related to voluntary relaxation performed with the more affected limb, a delayed mu and beta ERD and a disappearance of beta ERS were revealed. These results demonstrate that the pattern of cortical oscillatory activity in a relaxation task is abnormal in parkinsonian patients. The authors suggest that this may be due to anomalous activity in inhibitory motor cortical systems and impaired sensorimotor integration of afferent inputs from muscle and joint receptors.     

Lateralization of event-related beta desynchronization in the EEG during pre-cued reaction time tasks.

OBJECTIVE: Here, we investigate whether the event-related desynchronization (ERD) of spectral components of the cortical EEG in the beta (13-30 Hz) frequency range may, in part, index motor selection processes. Specifically, we sought evidence for a contralaterally dominant component of the beta ERD that is limited to trials in which motor selection is possible prior to any imperative cue to move, with attendant behavioural advantage. METHODS: We measured reaction time and assessed the lateralization of beta ERD in 12 healthy volunteers as they performed pre-cued choice reaction time tasks, in which warning S1 cues were either fully predictive about the laterality of a subsequent imperative S2 signal or provided no laterality information. We calculated 'lateralized ERD index' (LERDI), a parallel measure to the lateralized readiness potential in the time domain. RESULTS: Trials with 100% S1-S2 congruency produced significantly shorter reaction times than trials with 50% S1-S2 congruency, where laterality information was unreliable. Beta LERDI indicated significantly greater lateralisation of the ERD in the warning-go interval and of event-related synchronization (ERS) following movement in the 100% condition than in the 50% condition. The lateralization of the beta ERD with respect to hand persisted, even when subjects were instructed to make movements of opposite laterality to those prompted. CONCLUSIONS: Lateralized EEG changes occur in the beta band in the S1-S2 interval prior to movement, but only when informative warning cues allow early motor selection, as suggested by the shortening of reaction time. Furthermore, the enhanced contralateral ERS with 100% S1-S2 congruency suggests that this phenomenon is at least partly independent of afferent feedback, as the same movement was made in the 100 and 50% conditions. SIGNIFICANCE: Lateralized suppression of beta power prior to externally generated movements is associated with motor selection.     

Spatiotemporal patterns of beta desynchronization and gamma synchronization in corticographic data during self-paced movement.

OBJECTIVE: To study the spatiotemporal pattern of event-related desynchronization (ERD) and event-related synchronization (ERS) in electrocorticographic (ECoG) data with closely spaced electrodes. METHODS: Four patients with epilepsy performed self-paced hand movements. The ERD/ERS was quantified and displayed in the form of time-frequency maps. RESULTS: In all subjects, a significant beta ERD with embedded gamma ERS was found. CONCLUSIONS: Self-paced movement is accompanied not only by a relatively widespread mu and beta ERD, but also by a more focused gamma ERS in the 60-90 Hz frequency band.     

Watching object related movements modulates mirror-like activity in parietal brain regions

ObjectiveWe studied the activation of cortical motor and parietal areas during the observation of object related grasping movements. By manipulating the type of an object (realistic versus abstract) and the type of grasping (correct versus incorrect), we addressed the question how observing such object related movements influences cortical rhythmicity, especially the mu-rhythm, in the context of an “extended” human mirror neuron system (MNS).MethodsMultichannel electroencephalogram (EEG) was recorded during the observation of different object-related grasping actions in twenty healthy subjects. Different movies were presented, showing sequences of correct or incorrect hand grasping actions related to an abstract or realistic (daily life) object.ResultsEvent-related de/synchronization (ERD/ERS) analyses revealed a larger ERD in the upper alpha (10–12 Hz), beta (16–20 Hz) and gamma (36–40 Hz) frequency bands over parietal brain regions depending on the type of grasping. The type of object only influenced ERD patterns in the gamma band range (36–40 Hz) at parietal sites suggesting a strong relation of gamma band activity and cortical object representation. Abstract and realistic objects produced lower beta band synchronization at central sites only, whereas depending on the type of grasping an ERS in the upper alpha band (10–12 Hz) was observed.ConclusionDepending on the type of the grasped object and the type of grasping stronger parietal cortical activation occurred during movement observation.SignificanceDiscussing the results in terms of an “extended” human mirror neuron system (MNS), it could be concluded that beside sensorimotor areas a stronger involvement of parietal brain regions was found depending on the type of object and grasping movement observed.