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PubMed2004

Long-lasting modulation of human motor cortex following prolonged transcutaneous electrical nerve stimulation (TENS) of forearm muscles: evidence of reciprocal inhibition and facilitation.

Several lines of evidence indicate that motor cortex excitability can be modulated by manipulation of afferent inputs, like peripheral electrical stimulation. Most studies in humans mainly dealt with the effects of prolonged low-frequency peripheral nerve stimulation on motor cortical excitability, despite its being known from animal studies that high-frequency stimulation can also result in changes of the cortical excitability. To investigate the possible effects of high-frequency peripheral stimulation on motor cortical excitability we recorded motor-evoked potentials (MEPs) to transcranial magnetic stimulation (TMS) of the left motor cortex from the right flexor carpi radialis (FCR), extensor carpi radialis (ECR), and first dorsal interosseous (FDI) in normal subjects, before and after transcutaneous electrical nerve stimulation (TENS) of 30 min duration applied over the FCR. The amplitude of MEPs from the FRC was significantly reduced from 10 to 35 min after TENS while the amplitude of MEPs from ECR was increased. No effects were observed in the FDI muscle. Indices of peripheral nerve (M-wave) and spinal cord excitability (H waves) did not change throughout the experiment. Electrical stimulation of the lateral antebrachial cutaneous nerve has no significant effect on motor cortex excitability. These findings suggest that TENS of forearm muscles can induce transient reciprocal inhibitory and facilitatory changes in corticomotoneuronal excitability of forearm flexor and extensor muscles lasting several minutes. These changes probably may occur at cortical site and seem to be mainly dependent on stimulation of muscle afferents. These findings might eventually lead to practical applications in rehabilitation, especially in those syndromes in which the excitatory and inhibitory balance between agonist and antagonist is severely impaired, such as spasticity and dystonia.

Adult↗

PubMed2002

Reduced inhibition within primary motor cortex in patients with poststroke focal motor seizures.

BACKGROUND: Following an ischemic brain lesion, the affected cortex undergoes structural and functional changes that may lead to increased cortical excitability or decreased inhibitory neuronal activity, resulting in the occurrence of poststroke epileptic seizures in 6 to 10% of patients with stroke. METHODS: To assess motor cortical excitability, transcranial magnetic stimulation (TMS) was used to determine the silent period (SP) duration in 84 consecutive patients with ischemic stroke. RESULTS: In a subpopulation of six patients (38 to 72 years old) a significant decrease of the SP duration (mean 116 +/- 14 msec) was detected in either the arm or the leg on the affected side as compared to the corresponding unaffected limb (mean 231 +/- 32 msec). This electrophysiologic abnormality was clinically associated with focal motor seizures in five of the six patients, whereas none of the other 76 patients with normal or prolonged SP durations developed seizures or epilepsy. CONCLUSIONS: Silent period shortening in this group reflects decreased inhibitory activity that may partly be related to functional or structural impairment of GABAergic interneurons. TMS may be of value for determining patients with stroke at risk for developing poststroke seizures.

Adult↗

PubMed1988

Premotor and supplementary motor cortex in rhesus monkeys: neuronal activity during externally- and internally-instructed motor tasks.

We compared neuronal activity in the premotor (PM) and supplementary motor cortex (SM) of two rhesus monkeys as they performed two tasks. In an externally-instructed task, a visuospatial instruction stimulus indicated which of two touch pads should be the target of a forelimb movement. In an internally-instructed task, the visuospatial stimulus was either irrelevant or not presented, but in either case the target alternated between the two touch pads in blocks of 20 trials each. In both tasks, the monkey withheld movement for a self-timed delay period. Neuronal activity modulation during the delay period (set-related activity) and immediately before movement (movement-related activity) was comparable in PM and SM, both in terms of the proportion of cells with both of those activity patterns and their depth of modulation. Thus, our findings do not provide strong support for a clear-cut functional division between PM and SM regarding the control of externally- and internally-instructed limb movements. Within PM, 57 out of 96 cells with set-related activity showed similar modulation during the two tasks, supporting the proposition that such activity contributes to the preparation for a limb movement. In 32 of the 39 PM set-related neurons that showed a significant activity difference between the two tasks, activity was greater in the externally-instructed task. This finding supports the hypothesis that set-related activity in PM contributes more to sensorially-instructed than to other movements.

Animals↗

PubMed2001

Transient inhibition of the human motor cortex by capsaicin-induced pain. A study with transcranial magnetic stimulation.

Motor evoked potentials (MEPs) to transcranial magnetic stimulation (TMS) of the left motor cortex were recorded from the right first dorsal interosseous (FDI), abductor pollicis brevis (APB), abductor digiti minimi (ADM), flexor carpi radialis (FCR), extensor carpi radialis (ECR) in 17 normal subjects, before and after painful application of capsaicin on the skin overlying the right FDI and FCR muscles. The amplitude of MEPs from the FDI and FCR was significantly reduced from 20 to 30 min after the application of capsaicin over the FDI and FCR muscles, respectively, then progressively returned to the basal values. A similar trend of MEPs inhibition was observed for APB and FCR muscles, but this reduction was not significant. Indices of peripheral nerve (M-wave) and spinal cord excitability (F and H waves) did not change throughout the experiments. Motor cortex inhibition induced by tonic cutaneous pain is maximal to muscles adjacent to the painful area. This inhibition may be due to the activation of the C fibres which mediate 'slow' nociception and might be important to alert subject to possible phasic nociceptive events that may occur close to the painful area.

Adult↗

PubMed2004

Motor cortex excitability in Alzheimer's disease and in subcortical ischemic vascular dementia.

Twenty Alzheimer's disease (AD) patients, 20 subcortical ischemic vascular dementia (SIVD) patients and 20 neurologically and cognitively normal subjects underwent transcranial magnetic stimulation to study motor cortex excitability changes. Motor threshold (MT), amplitude of motor evoked potentials, silent period and the H/M ratio (amplitude of maximal Hoffman reflex vs. that of maximal motor response) were considered. MT was lower in SIVD patients when compared with AD patients (P = 0.003) and the control group (P < 0.001) and lower in AD patients when compared with the control group (P < 0.001). The increment of motor cortex excitability in AD and SIVD did not lead us to distinguish clearly the two types of dementia. It is likely that the electrophysiological similarity between AD and SIVD could represent another common mechanism shared from these forms of dementia.

Aged↗

PubMed2006

Absence of postexercise and delayed facilitation of motor cortex excitability in restless legs syndrome: evidence of altered cortical plasticity?

STUDY OBJECTIVE: Restless legs syndrome (RLS) is a neurologic disorder with well-defined clinical and diagnostic criteria but the pathophysiology of which is unclear. Previous studies have suggested alterations in motor cortex function in RLS. We aimed to compare motor cortex plasticity in subjects with RLS versus healthy controls. DESIGN: Biphasic single-pulse transcranial magnetic stimulation (TMS) of the nondominant hemisphere was used to define motor evoked potential (MEP) amplitude, motor threshold, and silent period. Subjects also performed 3 blocks (30-s, 60-s, and 90-s duration) of a bimanual motor task (exercise condition). Amplitude of MEPs elicited immediately after each block, and then after a 15-minute rest period were compared with baseline. The time course of intracortical inhibition was also tested using paired-pulse TMS at 1- to 6-millisecond interstimulus intervals. SETTING: Clinical neurophysiology laboratory in a General Hospital. STUDY PARTICIPANTS: For the single-pulse TMS procedures, the RLS group included 11 patients affected by primary RLS and the control group included 11 age- and sex-matched normal subjects. For the paired-pulse TMS procedures, there were 9 patients and 6 controls. INTERVENTIONS: None. RESULTS: There were no group differences in motor threshold and MEP amplitudes, but the silent period was significantly shorter in subjects with RLS. Compared with baseline, control subjects had larger MEP amplitudes after 30 and 60 seconds of exercise and also after the rest period. In contrast, MEP amplitudes in patients with RLS were not significantly different from baseline after any of the exercise conditions or following the rest period. Patients with RLS also had decreased short-latency paired-pulse inhibition. CONCLUSIONS: Findings show abnormal motor cortex inhibition and cortical excitability differences in RLS. We suggest the possibility of alterations in movement-related cortical plasticity in RLS.

Arousal↗

PubMed2001

Monitoring of intraoperative motor evoked potentials to increase the safety of surgery in and around the motor cortex.

OBJECT: The repetitive application of high-frequency anodal monopolar stimulation during surgery in or near the motor cortex allows a qualitative and quantitative evaluation of motor evoked potentials (MEPs). Using this method, motor pathways and motor function can be continuously monitored during surgery. METHODS: In this prospective study, 70 patients underwent MEP monitoring during surgery performed in the central region. All procedures were performed after general anesthesia had been induced without the aid of muscle relaxants. The motor pathways were monitored during the entire surgical procedure by repetitive high-frequency anodal monopolar stimulation (frequency 400-500 Hz; train 7-10 pulses; impulse duration 0.2-0.7 msec; and stimulation intensity 16.9 +/- 7.76 mA). The MEPs were continuously evaluated to assess their latency, potential duration, and amplitude. Recorded alterations in these parameters were subsequently correlated with surgical maneuvers and with postoperative neurological deterioration. The monitoring parameters (latency, potential duration, and amplitude) had a broad interindividual range of variation. A correlation between individual intraoperative changes in the potentials and surgical maneuvers or postoperative neurological deterioration was observed in eight cases. A spontaneous shift in latency greater than 15% or a sudden reduction in the amplitude of the potential greater than 80% was considered a warning criterion. In all cases in which there was an irreversible change in latency or a complete loss of potentials were observed, there was postoperative neurological deterioration. CONCLUSIONS: Improved surgical safety can be achieved using intraoperative neurophysiological monitoring procedures. Repetitive stimulation of the motor cortex proved to be a reliable method for monitoring subcortical motor pathways. Changes in MEP latency and MEP amplitude served as warning criteria during surgery and possessed prognostic value.

Adolescent↗

PubMed2000

Role of sensory deficits in motor impairments after injury to primary motor cortex.

After a focal ischemic lesion in the hand representation of the primary motor cortex in squirrel monkeys, manual skill was mildly and transiently impaired on a reach-and-retrieval task. Performance was significantly poorer during weeks 1 and 3 post-lesion, but was normal by week 4. An unusual behavioral event was also observed after the lesion. Monkeys reached for pellets, but visually inspected the hand for the presence of the pellets, even when none were actually retrieved. This behavior, possibly indicative of a sensory deficit, was rarely observed prior to the lesion, but was observed at significantly higher levels during week one post-lesion. These results suggest that the primary motor cortex plays a significant role in somatosensory processing during the execution of motor tasks. Motor deficits heretofore identified as purely motor, may be at least partially due to a sensory deficit, or sensory-motor disconnection.

Analysis of Variance↗

PubMed2004

Synaptic plasticity of local connections in rat motor cortex.

This paper reviews studies that investigated mechanisms of the induction of long-term synaptic efficacy increase in local horizontal connections in slices of adult rat motor cortex. Long-term potentiation (LTP) could be induced by electrical stimulation of afferents using theta burst stimulation (TBS) conditionally, when synaptic inhibition was transiently blocked by focal application of GABA(A) receptor antagonist. Robust, long-lasting enhancement of synaptic transmission in horizontal connections was induced by brief application of the potassium channel blocker, tetraethylammonium (TEA, 25 mM), to the incubation medium. This TEA-LTP could be blocked by nifedipine, a voltage-dependent calcium channel blocker. A transient exposure of slices to elevated extracellular calcium (5 mM) resulted in a long-lasting enhancement of responses, termed Ca-LTP, which could be blocked by the antagonist of NMDA receptors, APV. The induction of both TEA-LTP and Ca-LTP, could be prevented by inhibitors of the extracellular signal regulated kinase (ERK) cascade U0126 and PD98059. A transient activation of the ERK, 15 min after application of TEA or elevated [Ca2+], was demonstrated using immunofluorescence. Both forms of plasticity could also be prevented by the inhibitor of cAMP-dependent protein kinases (PKA), Rp-cAMPS. These studies indicate the involvement of the ERK and PKA signaling mechanisms in synaptic plasticity of the motor cortex in vitro. Since LTP in horizontal connections of the motor cortex has previously been shown to be related to the acquisition of a motor skill, it is suggested that the ERK and PKA signaling pathways may be involved in motor learning.

Animals↗

PubMed1991

The pathway from Ia forelimb afferents to the motor cortex: a new hypothesis.

Forelimb target-reaching and food-taking in cats depend on different interneuronal circuitry in the spinal cord. On the basis of previous findings regarding the effect of transection of the corticospinal tract in the spinal cord, of high dorsal column (DC) transection, of low pyramidotomy and of pyramidotomy after previous DC transection, it is proposed that the food-taking movement is temporally linked to target-reaching as follows: During target-reaching, the position of the paw is signalled by the pathway from forelimb proprioceptors (mainly Ia) to the motor cortex with a relay in the main cuneate nucleus. The command for food-taking is issued by the motor cortex only when the pathway from the forelimb signals that the paw approaches the target correctly, as may be determined by a comparison of the information from the forelimb with an efference copy of the motor program for target-reaching. The hypothesis is based on previous results regarding the organization of the pathway from the forelimb to area 3a and the motor cortex, and regarding the cortico-cuneate pathway with selective projection from area 3a and motor cortex to the basal caudal part of the cuneate nucleus, where the proprioceptive information from the forelimb is relayed. Results relevant to the present hypothesis regarding responses of precentral neurones during active and passive movements in awake animals are briefly discussed.

Animals↗

PubMed1988

Cognitive spatial-motor processes. 2. Information transmitted by the direction of two-dimensional arm movements and by neuronal populations in primate motor cortex and area 5.

We measured the amount of information transmitted by the direction of two-dimensional (2-D) arm movements of human subjects, and by neuronal populations in the motor cortex and area 5 of monkeys. We also compared the information transmitted by a motor cortical population when the predictability of the direction of movement was varied, i.e. when the target of the movement was the same, or different, in successive trials. The information transmitted by a neuronal population was measured using the "population vector" code (Georgopoulos et al. 1983, 1986) as the stimulated directional output of the population. We found the following. (a) The information transmitted per movement increased in all cases with input information but more slowly than the maximum possible. No asymptote had been reached at 6.64 bits of input information; the best human performance at that level was 4.5 bits. (b) The average information transmitted by a motor cortical population (N = 253 cells) was approximately 0.5 bits higher than that of best human performance at all levels of input information. These findings indicate that whereas information loss at the level of motor cortex, and during stages preceding it, increases with increasing input information, this loss remains constant at all levels of input information during processes intervening between motor cortex and movement. (c) The information transmitted by the neuronal population at a constant level of input information increased with the number of cells in the population and had not plateaued at the population size of 253 cells used in this study. (d) Consistently higher amounts of information were transmitted by motor cortical than by area 5 populations at all levels of input information (up to 7 bits) examined. The difference was approximately 0.16 bits. (e) Finally, the information transmitted by a motor cortical population was slightly higher (by 0.07 bits) when the movement was more than less predictable. Although this difference was small, it was consistent at all levels of input information (3-7 bits) and was statistically highly significant (p less than 0.005, paired t test). These results establish the information theoretical approach as a useful method for comparing (a) behavioral and neural data, (b) neural data between different brain areas, and (c) neural data obtained under different behavioral manipulations.

Adult↗

PubMed1996

Electrophysiological and morphological properties of pyramidal and nonpyramidal neurons in the cat motor cortex in vitro.

Electrophysiological and morphological properties of the neurons in cat motor cortex were investigated using intracellular recording and staining techniques in a brain slice preparation. In response to intracellular injection of depolarizing current pulses, four distinct types of firing patterns were observed among cat neocortical neurons. Regular-spiking neurons were characterized by their repetitive firing from which conspicuous frequency adaptation was observed. Doublet-or-burst firing cells were marked with their tendency to fire 2-5 clustered spikes at the onset of depolarizing pulse. In doublet-or-burst firing neurons, but not in regular-spiking neurons, a low-threshold calcium current was revealed by single-electrode voltage clamp. Both regular-spiking and doublet-or-burst firing neurons had relatively wide action potentials. Fast-spiking neurons could fire extremely narrow action potentials at a very high frequency. Their frequency-to-intensity slope of steady-state firing was significantly higher than that of the other neurons. In contrast, narrow-spiking neurons had the smallest frequency-to-intensity slope for steady-state firing, although their action potentials were as narrow as those of the fast-spiking neurons. Both regular-spiking and doublet-or-burst firing neurons were identified as pyramidal neurons, and were found in all layers below layer I. Their apical dendrites were densely coated with dendritic spines. Narrow-spiking neurons were only recorded in layer V. They were large pyramidal cells with scare spines on their apical dendrites. Fast-spiking neurons were all nonpyramidal interneurons. Seven out of eight labelled fast-spiking cells had beaded dendrites without spines. Their axons had a large number of varicosities, and arborized extensively to form a dense plexus of terminals in the vicinity of their soma. The remaining neuron was found to be a spiny nonpyramidal neuron in layer V. These results demonstrate that, in addition to the three types of firing patterns previously identified in rodent neocortex, a group of neurons in the cat motor cortex express another type of firing behaviour which is characterized by extremely narrow action potential and very small frequency-to-intensity slope. Correlation with the morphological data shows that these neurons are large layer V pyramidal cells rather than nonpyramidal interneurons.

Action Potentials↗

PubMed1991

Acute effects of alcohol on unit activity in the motor cortex of freely moving rabbits: comparison with the limbic cortex.

Unit activity was recorded from the motor cortex of eight freely moving rabbits in order to examine the acute effect of ethanol (1 g kg-1) on organization of unit activity and to compare it with our earlier results from the limbic cortex. The rabbits performed a food-acquisition task in the experimental cage. Unit activity was recorded during behaviour in the control experiment followed by the alcohol experiment on the next day. After ethanol, behavioural mistakes and the duration of the behavioural cycle significantly increased. In the control experiments activation of 58% of the units had no constant relation to the phases of the behavioural cycle (non-involved units), whereas 42% of the units were constantly activated during certain phases (involved units). Two per cent of the latter units were activated in relation to newly learned behavioural acts (e.g. pedal pressing; L units), 28% in relation to food seizure and/or grinding (S units) and 12% in relation to certain movements during different behavioural acts (M units). Ethanol had no effect on the number of active units and the same relation between the number of non-involved and involved units or between the number of different types of involved units was found. However, the number of involved units decreased in the upper and increased in the lower cortical layers. Also the number of units with low background frequency increased, although the frequency within activations did not change. In our earlier study the number of active units in the limbic cortex decreased after ethanol by one third and the relation between the number of L and M units was reversed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1997

Pharmacological classification of central post-stroke pain: comparison with the results of chronic motor cortex stimulation therapy.

In an attempt to clarify the neurochemical background of central post-stroke pain and to undertake a pharmacological analysis, the basic pharmacological characteristics of this intractable pain syndrome were investigated by the morphine, thiamylal and ketamine tests. In addition, the correlation between the pharmacological characteristics and the effects of chronic motor cortex stimulation therapy was examined. The study employed 39 central post-stroke pain patients who had intractable hemibody pain associated with dysesthesias, and radiologically demonstrated lesions in the thalamic area (thalamic pain, n = 25) or suprathalamic area (suprathalamic pain, n = 14). The pharmacological evaluations showed that definite pain reduction occurred in eight of the 39 cases (20.5%) by the morphine test, in 22 of the 39 cases (56.4%) by the thiamylal test, and in 11 of 23 cases (47.8%) by the ketamine test. Based on these pharmacological assessments, there was no obvious difference between thalamic and suprathalamic pain. A comparison of the long-term follow-up results of chronic motor cortex stimulation therapy revealed that thiamylal and ketamine-sensitive and morphine-resistant cases displayed long-lasting pain reduction with chronic motor cortex stimulation therapy, whereas the remaining cases did not show good results. We conclude that pharmacological classification of central post-stroke pain by the morphine, thiamylal and ketamine tests could be useful for predicting the effects of chronic motor cortex stimulation therapy. It has recently been suggested that excitatory amino acids may be involved in the development of central post-stroke pain. However, the fact that only 23 of the present 39 cases (59.0%) of thalamic and suprathalamic pain were sensitive to the thiamylal or ketamine test reflects the complex pharmacological background and the difficulties associated with treating central post-stroke pain.

Adult↗

PubMed2000

I-waves in motor cortex.

I-waves refer to high-frequency (approximately 600 Hz) repetitive discharge of corticospinal fibers produced by single-pulse stimulation of the motor cortex. First detected in animal preparations, this multiple discharge can also be recorded in humans with epidural electrodes over the spinal cord, and with recently developed noninvasive paired-pulse transcranial magnetic stimulation protocols. The exact nature of the generation of I-waves is still unclear, but there is convincing evidence that they originate in the motor cortex, mainly through activation of corticocortical projections onto corticospinal neurons. The ability to measure I-waves in human motor cortex allows one to test the integrity and excitability of the underlying corticocortical circuits in health and disease.

Humans↗

PubMed1999

Long-term reorganization of motor cortex outputs after arm amputation.

OBJECTIVE: To investigate the reorganization of the corticospinal system long after arm amputation at different levels. METHODS: Focal transcranial magnetic stimulation (TMS) was performed in 15 patients 21 to 65 years after arm amputation at the level of the forearm, upper arm, or shoulder. Cortically elicited electromyographic responses were investigated in muscles immediately proximal to the stump. TMS was performed on a skull surface grid overlying the motor cortex. The response threshold, number of effective stimulation sites, and the sum of the amplitudes elicited at these sites were evaluated for slightly contracted muscles. RESULTS: Seven of eight patients with forearm amputation had larger stimulation effects in the biceps supplied by the motor cortex contralateral to amputation, as indicated by variable patterns of lowered response thresholds, increased response amplitudes, or increased numbers of effective stimulation sites. In seven patients with a more proximal amputation, the motor responses were investigated in the deltoid and trapezoid muscle. In only two of them, the motor cortex contralateral to amputation showed an increased excitability. Three patients presented with a higher excitability of the motor cortex contralateral to the intact arm and two with a balanced type of excitability. CONCLUSION: Reorganization of the motor system can be present more than 20 years after amputation. Furthermore, differential patterns of reorganized corticospinal output were found for different stump muscles, which might be due to varying amounts of ipsilateral corticospinal projections.

Adult↗

PubMed1999

Motor cortex localization using functional MRI and transcranial magnetic stimulation.

OBJECTIVE: Congenital brain lesions producing focal seizures may be accompanied by reorganization of the areas responsible for motor and sensory functions within the brain due to a phenomenon that has been termed "neuronal plasticity." This can be studied using functional MRI (fMRI) and transcranial magnetic stimulation (TMS). Using either method, the motor cortex can be localized noninvasively, but to date there have been few studies correlating the level of agreement between the two techniques. METHODS: We used fMRI and TMS to localize the motor cortex in a young woman with intractable focal seizures, congenital left arm weakness, and a dysplastic right hemisphere on MRI. RESULTS: There was excellent agreement in the localization of motor representation for each hand. Both were predominantly located in the left hemisphere. fMRI also showed an area of posterior activation in the right hemisphere, but there was no evidence of descending corticospinal projections from this site using TMS, direct cortical stimulation, and Wada testing. CONCLUSIONS: Functional MRI (fMRI) and transcranial magnetic stimulation (TMS) were successfully used to localize cortical motor function before epilepsy surgery. Each technique demonstrated migration of motor function for the left hand to the left motor cortex. After resection of the dysplastic right precentral gyrus there was no permanent increase in weakness or disability. The two techniques are complementary; fMRI indicates all cortical areas activated by the motor task, whereas TMS identifies only those areas giving rise to corticospinal projections.

Adult↗

PubMed2005

Task-dependent oscillations during unimanual and bimanual movements in the human primary motor cortex and SMA studied with magnetoencephalography.

The neural mechanisms subserving uni- and bimanual control of movements are not well understood. Nevertheless, recent studies indicate a functional role of oscillatory activity in movement control and point towards a hemispheric asymmetry in motor control. This study specifically addresses the issues of (i) task-relatedness, (ii) hemispheric symmetry, and (iii) frequency specificity of the measures power, cerebro-muscular coherence, and cerebro-cerebral coherence in bilateral primary motor cortex and supplementary motor area (SMA). We have studied 10 right-handed subjects with simultaneous recordings of magnetoencephalography and surface electromyography during different unimanual and bimanual tasks. Using the analysis technique Dynamic Imaging of Coherent Sources (DICS), left and right primary motor cortex and SMA were functionally localized. Power, cerebro-musclar coherence, and cerebro-cerebral coherence between these areas were computed for four frequency bands in each condition and subjected to ANOVA. Results show a task-specific modulation of power and coherence, and further indicate a hemispheric asymmetry in the control of unimanual and bimanual movements. In addition, different frequency bands showed different task-dependent variations. The gamma band (26-40 Hz) showed strongest modulation for cerebro-muscular coherence and was strongest for the isometric contraction conditions. In contrast, the beta band (13-24 Hz) showed the strongest variations between static and dynamic conditions, and seems to play a particular role in movement control. In summary, our results indicate a differential functional role of oscillatory activity and coupling in the motor system.

Adult↗