Brain activity preceding a 2D manual catching task

We investigated the event-related desynchronization (ERD) and synchronization (ERS) properties of cortical EEG rhythms in regions of interest (ROI) during the preparation of a 2D task for manual catching of a moving object. EEG signals were recorded through a 32-channel system in eleven healthy subjects during the interception task consisting of 2D catching with the right hand of a handle moving at constant velocity (1.5 m/s) on a predefined straight trajectory. The first session of catching movements (CATCHING_PRE) was compared with a second session after 1 h with identical characteristics (CATCHING_POST) and with other two conditions, where the subjects had to reach and grasp the handle fixed in the medium of platform (REACHING) and they looked at the object moving without catching it (GAZE TRACKING). Changes of cortical rhythms were correlated with dynamic and kinematic indexes of motor performance in both catching sessions.Movements requiring different strategies (predictive versus prospective) are supported by specific changes of cortical EEG rhythms: in the CATCHING condition a more evident power decrease (ERD) in alpha 2 and beta band in the sensorimotor region contralateral to the catching hand was observed, while in the REACHING one a bilateral ERD in beta band was found. Motor learning and movement automatization were characterized by a significant reduction of theta ERS in the anterior cingulate cortex (ACC), a ROI linked to focused attention, and with a shift of neuronal activation in alpha 2 band from the bilateral superior parietal areas to the homologous area of the left hemisphere. Finally, our EEG findings are consistent with the role of supplementary motor (SMA), premotor and prefrontal areas in motor planning and preparation. In particular, theta ERS in left SMA significantly correlated with an improvement of motor performance, as evidenced by its correlation with the training-related reduction of interception time (IT).     

Task-specific modulation of effective connectivity during two simple unimanual motor tasks: a 122-channel EEG study

Neural oscillations are thought to underlie coupling of spatially remote neurons and gating of information within the human sensorimotor system. Here we tested the hypothesis that different unimanual motor tasks are specifically associated with distinct patterns of oscillatory coupling in human sensorimotor cortical areas. In 13 healthy, right-handed subjects, we recorded task-induced neural activity with 122-channel electroencephalography (EEG) while subjects performed fast self-paced extension-flexion movements with the right index finger and an isometric contraction of the right forearm. Task-related modulations of inter-regional coupling within a core motor network comprising the left primary motor cortex (M1), lateral premotor cortex (lPM) and supplementary motor area (SMA) were then modeled using dynamic causal modeling (DCM). A network model postulating coupling both within and across frequencies best captured observed spectral responses according to Bayesian model selection. DCM revealed dominant coupling within the β-band (13-30 Hz) between M1 and SMA during isometric contraction of the forearm, whereas fast repetitive finger movements were characterized by strong coupling within the γ-band (31-48 Hz) and between the θ- (4-7 Hz) and the γ-band. This coupling pattern was mainly expressed in connections from lPM to SMA and from lPM to M1. We infer that human manual motor control involves task-specific modulation of inter-regional oscillatory coupling both within and across distinct frequency bands. The results highlight the potential of DCM to characterize context-specific changes in coupling within functional brain networks.     

Fatigue in Multiple Sclerosis Is Associated with Abnormal Cortical Activation to Voluntary Movement—EEG Evidence

Converging evidence is consistent with the view that fatigue in Multiple Sclerosis is independent from pyramidal tract involvement, suggesting a possible involvement of frontal areas. During voluntary movement, changes of the EEG rhythms can be observed over sensorimotor areas. Event-related desynchronization (ERD) of the 10 and 20 Hz frequency bands occurs during motor planning and execution and is followed after movement termination by event-related synchronization (ERS), expressing cortical idling or inhibition. We evaluated the pattern of cortical activation to voluntary movement in MS patients complaining of fatigue assessed using the Fatigue Severity Scale. Fifteen MS patients complaining of fatigue, 18 MS patients without fatigue, and 14 normal controls were studied. The two patients groups were similar for age, sex, disease duration, and were not disabled (score <1.5 at the Expanded Disability Status Scale). Twenty-nine channel EEG was recorded during about 60 self-paced extensions of the right thumb. The onset latency and amount of the contralateral sensorimotor (C3 electrode) 10 and 18–22 Hz ERD were similar in the three groups. ERD was more widespread anteriorly in the fatigue group compared with normal controls (P < 0.01 over Fz electrode). Postmovement contralateral sensorimotor 18–22 Hz ERS was significantly lower in fatigue MS patients compared with normal subjects (P < 0.005) and with nonfatigue MS patients (P = 0.02). These findings are consistent with a central origin of fatigue in MS and indicate cortical dysfunction even during a simple motor task, resulting in hyperactivity during movement execution and failure of the inhibitory mechanisms intervening after movement termination.     

Human cortical electroencephalography (EEG) rhythms during the observation of simple aimless movements: a high-resolution EEG study

In the present high-resolution electroencephalographic (EEG) study, we computed event-related desynchronization and synchronization (ERD/ERS) of alpha (about 10 Hz) and beta (about 20 Hz) rhythms in association with the execution (with visual feedback) and observation of brisk unilateral right and left aimless finger movements. A first scope was to test the topographical "functional equivalence" of cortical rhythmicity related to movement execution and observation, which would represent an ideal cortical observation/execution matching system. A second scope was to evaluate the hypothesis of a left or right hemisphere prevalence of the cortical rhythmicity related to the movement observation compared to the movement execution. EEG (128 electrodes) was recorded in 10 healthy right-handed volunteers. Surface Laplacian estimation spatially enhanced EEG data over a MRI-constraint head model. Under both conditions, ERD peaked during the movement execution or observation and was replaced by a ERS "rebound" or "recovery," which peaked during the postevent period. Topographical results are in favor of a "functional equivalence" (i.e., similar ERD/ERS values in magnitude and timing) of alpha and beta rhythmicity in central scalp regions overlying premotor/primary sensorimotor cortex. On the contrary, the functional equivalence of alpha rhythmicity was negligible (i.e., different ERD/ERS values in magnitude and timing) in parietal-occipital scalp regions overlying posterior parietal and parieto-occipital cortex, which could be the neural substrate to distinguish among the own motor intensions and others' aimless movements (i.e., visuomotor transformation integrated with sensorimotor, postural, and kinematics representations). Finally, the pattern of hemispherical cortical rhythmicity did not support a "simple concentration" of movement observation functions in the left or right hemisphere.     

Cortical activity in multiple motor areas during sequential finger movements: an application of independent component analysis

Multiple cortical regions such as the supplementary motor area (SMA), premotor cortex (PM), and primary motor cortex (M1) are involved in the sequential execution of hand movements, but it is unclear how these areas collaborate in the preparation and execution of ipsilateral and contralateral hand movements. In this study, we used right-handed subjects to examine the spatial distribution and temporal profiles of motor-related activity during visually cued sequential finger movements by applying independent component analysis (ICA) to event-related functional magnetic resonance imaging (fMRI) signals. The particular merit of the ICA method is that it allows brain activity in individual subjects to be elucidated without making a priori assumptions about the anatomical areas that are activated or the temporal profile of activity. By applying ICA, we found that (1) the SMA contributed to both the preparation and execution of movements of the right and left hand; (2) the left M1 and dorsal premotor cortex (PMd) contributed to both the preparation and execution of movements of the right and left hand, whereas the right M1 and PMd contributed mainly to the execution of movements of the left hand; (3) pre-SMA areas were activated in some subjects in concert with the posterior parietal and prefrontal cortex; and (4) fMRI signals over superficial cortical draining veins could be distinguished from cortical activation. We suggest that ICA is useful for categorizing distributed task-related activities in individual subjects into several spatially independent activities that represent functional units in motor control.     

Cortical Alpha Rhythms Are Related to the Anticipation of Sensorimotor Interaction Between Painful Stimuli and Movements: A High-Resolution EEG Study

We tested whether cortical activation anticipating painful stimuli is reduced more by integrative processes on somatosensory painful and motor information relative to the same hand than when that information refers to different hands. In 3 conditions, visual warning stimuli were followed by visual target stimuli associated with an electrical painful stimulation at left index finger. In the Pain (control) condition, no task was required after the target stimuli. In the “Pain + ipsilateral movement” condition, the subjects had to perform a movement of the left index finger. In the “Pain + contralateral movement” condition, they had to perform a movement of the right index finger. Meanwhile, electroencephalographic data were recorded (n = 18) from 128 scalp electrodes. Off line, these data were spatially enhanced by surface Laplacian transformation. Sensorimotor cortical activation before the painful stimulation was probed by the percentage power reduction of alpha rhythms at approximately 8 to 12 Hz (event-related desynchronization, ERD). Results showed that the subjects perceived a lower stimulus intensity in both “Pain + ipsilateral” and “Pain + contralateral” conditions compared with the control “Pain” condition. Furthermore, wide anticipatory alpha ERD (approximately 10–12 Hz) was lower in amplitude in the “Pain + ipsilateral” than in the “Pain + contralateral” condition. These results suggest that modulation of alpha rhythms is a putative physiological mechanism underlying anticipatory processes preceding the integration of painful and motor information at cortical level. Furthermore, these processes show a marked interference (“gating”) when the sensorimotor integration refer to the same hand as opposed to both hands.PerspectiveWe showed that cortical alpha rhythms preceding painful stimulation are influenced by the preparation of contralateral and ipsilateral finger movements. These results motivate further investigation for testing the hypothesis that chronic pain patients might exaggerate the anticipatory activation of sensorimotor cortex to negligible pain stimuli.     

Movement-related electroencephalographic reactivity in Alzheimer disease

Event-related desynchronization/synchronization (ERD/ERS) of alpha and beta electroencephalographic (EEG) rhythms was investigated in normal subjects and mild Alzheimer Disease patients (AD), performing unilateral right finger movements (about 10 s intermovement interval). Electroencephalographic data were sampled based on 10-20 system electrode montage. Surface Laplacian estimate of the potential reduced the head-volume conductor effects and annulled electrode reference variations. Results showed that EEG reactivity (i.e., ERD/ERS) of modeled contralateral rolandic cortex and motor performance were preserved in mild to moderate AD. In contrast, modeled activity (i.e., ERD/ERS) of frontolateral, centromedial, and ipsilateral rolandic areas was abnormal. Furthermore, interrelatedness of cortical response and movement timing was abnormal in AD patients. These results would support the working hypothesis that mild to moderate AD is a global brain network disease, including processing of sensorimotor information (despite no overt movement disorder). Further investigations will ascertain the clinical relevance of these results.     

Movement-related desynchronization of the cerebral cortex studied with spatially filtered magnetoencephalography

Event-related desynchronization (ERD) within the alpha and beta bands on unilateral index finger extension and hand grasping was investigated on six normal volunteers with magnetoencephalography (MEG). A novel spatial filtering technique for imaging cortical source power, synthetic aperture magnetometry (SAM), was employed for the tomographic demonstration of ERD. SAM source image results were transformed into statistical parametric images. On the same hand grasping task, a functional MRI (fMRI) study was conducted on two subjects and compared with the ERD result. When the MEG data were analyzed with the fast Fourier transformation, power attenuation within the alpha and beta bands was evident on the contralateral sensorimotor area just prior to movement onset. The tomographic distribution of ERD was clearly obtained with SAM statistical imaging analysis. The equivalent current dipole (ECD) for the signal-averaged motor field was localized to the hemisphere contralateral to the hand movement, roughly at the center of the region displaying beta-band ERD. The signal increase on fMRI roughly colocalized with the ERD on the contralateral sensorimotor area. In conclusion, with the novel spatial filtering technique for the brain magnetic field, SAM, cortical regions contributing to ERD on finger movement were successfully demonstrated in a tomographic manner. The relative colocalization of the contralateral SAM ERD with ECD as well as the fMRI activation suggests that SAM is a practically useful technique to extract event-related signals from brain noise.     

Post-movement beta rebound is generated in motor cortex: evidence from neuromagnetic recordings

Voluntary movements are accompanied by amplitude changes in cortical rhythms presumably as a result of functional activation of sensorimotor areas. Recently, the location of the neural generators involved in increasing power within the beta (15-30 Hz) frequency band following movement (post-movement beta rebound, PMBR) has come into question [Parkes, L.M, Bastiaansen, M.C.M, Norris, D.G., 2006. Combining EEG and fMRI to investigate the post-movement beta rebound. NeuroImage 29, 685-696.]. We used the synthetic aperture magnetometry (SAM) spatial filtering method to identify the time course and location of oscillatory changes within the beta and mu (8-14 Hz) frequency bands during the performance of voluntary movements. Neuromagnetic activity was recorded from 10 adult subjects during abduction of the right index finger. Changes in beta and mu source power were calculated for periods during and following movement, relative to pre-movement baseline activity. Decreases in beta band activity (event-related desynchronization, ERD) were observed during movement, with a strong increase (PMBR) beginning 230+/-170 ms following movement, lasting for 680+/-170 ms. Mu band ERD was observed both during and following movement, with little to no post-movement rebound. Beta and mu ERD were localized bilaterally to the hand region of postcentral gyrus whereas PMBR was localized bilaterally to the hand region of precentral gyrus (motor cortex). Both PMBR and beta ERD were strongest contralateral to the side of movement. These results provide further evidence that movement influences independent cortical rhythms in sensorimotor areas, and confirm previous reports of precentral generators of PMBR in the region of motor cortex, with postcentral generators of beta and mu ERD during movement.     

Anticipatory electroencephalography alpha rhythm predicts subjective perception of pain intensity.

This high-resolution electroencephalography (EEG) study tested the hypothesis that the suppression of rolandic alpha power before predictable painful stimulation affects the subject's subsequent evaluation of pain intensity, as a reflection of the influence of expectancy processes on painful stimulus processing. High-resolution EEG data were recorded (126 channels) from 10 healthy adult volunteers during the expectancy of a painful CO(2)-laser stimulation at the right wrist. Surface laplacian estimation enhanced the EEG spatial information content over 6 scalp regions of interest (left frontal, right frontal, left central, right central, left parietal, and right parietal areas). Spectral power was computed for 3 alpha sub-bands with reference to the individual alpha frequency peak (about 5-7 Hz for alpha 1, 7-9 Hz for alpha 2, and 9-11 Hz for alpha 3). The suppression of the alpha power before the painful stimulation [as reflected by the event-related desynchronization (ERD)] indexed the anticipatory cortical processes. Results showed maximum (negative) correlations between the alpha 2 and alpha 3 ERD amplitude at the left central area and the subjective evaluation of pain intensity (P < .001). The stronger the anticipatory alpha 2 and alpha 3 ERD, the higher the subjective evaluation of pain intensity. For alpha 3, that correlation was confirmed even when the effect of habituation across the recording session was taken into account. These results suggest that the anticipatory suppression of the alpha rhythms over the contralateral primary sensorimotor cortex predicts subsequent subjects' evaluation of pain intensity, in line with its crucial role for the discrimination of that intensity. PERSPECTIVE: This electroencephalographic study showed that anticipatory activation/deactivation of sensorimotor cortex roughly predicts subjective evaluation of pain. This motivates further investigation on possible implications for the understanding of central chronic pain. Chronic pain patients might exaggerate the anticipatory activation of sensorimotor cortex to negligible pain stimuli.     

正常人手指简单运动时脑功能区被激活的SPECT脑血流研究

目的运用单光子发射断层扫描仪(SPECT)对比观察不同年龄组正常人执行手指简单运动时脑内不同感兴趣区(ROI)的血流量变化,以期探讨运动功能区的作用。方法健康的志愿者18例,按照年龄划分为青年组和中老年组。每一受试对象分别安静和执行手指简单运动状态下进行99mTcECDSPECT扫描脑血流量测定。结果两组间的运动频率无明显差异,但中老年组的错误率显著高于青年组。运动激活后各脑叶的局部血流量无明显变化,而对侧初级运动区(M1)、同侧小脑、双侧辅助运动区(SMA)血流量显著变化。两组间相比,中老年组的对侧M1、同侧小脑的血流量增加低于年轻组,而双侧SMA则大于青年组(P<0.05)。结论手指的简单运动主要激活对侧M1、同侧小脑、双侧SMA;中老年组的SMA激活比青年组明显,显示中、老年人通过自身代偿机制调动更多的SMA参与运动的启动与执行。     

Activation of cortical areas in music execution and imagining: a high-resolution EEG study

Neuroimaging studies have shown that execution of a musical sequence on an instrument activates bilateral frontal opercular regions, in addition to bilateral sensorimotor and supplementary motor areas. During imagining activation of the same areas without primary sensorimotor areas was shown. We recorded EEG from 58 scalp positions to investigate the temporal sequence and the time course of activation of these areas while violin players prepared to execute, executed, prepared to imagine, or imagined a musical sequence on a violin. During the preparation for the sequence in three of seven musicians investigated the bilateral frontal opercular regions became active earlier than the motor areas and in one of them simultaneously with the motor areas. In two of the musicians a rather variable pattern of activation was observed. The frontal opercular regions were also strongly involved throughout the period of music execution or imagining. The supplementary motor area was involved in both preparation for the sequence and during execution and imagining of the sequence. The left primary sensorimotor area was involved in the preparation and termination of the musical sequence for both execution and imagining. The right sensorimotor area was strongly involved in the preparation for and during the execution of the sequence. We conclude that the bilateral frontal opercular regions are crucial in both preparation for and during music execution and imagining. They may have "mirror neurone" properties that underlie observation or imagining of one's own performance. The motor areas are differentially activated during the preparation and execution or imagining the sequence.     

Distraction affects frontal alpha rhythms related to expectancy of pain: an EEG study

Previous electroencephalographic (EEG) evidence has shown event-related desynchronization (ERD) of alpha rhythms before predictable painful stimuli, as a possible neural concomitant of attentional preparatory processes (Babiloni, C., Brancucci, A., Babiloni, F., Capotosto, P., Carducci, F., Cincotti, F., Arendt-Nielsen, L., Chen, A.C., Rossini, P.M., 2003. Anticipatory cortical responses during the expectancy of a predictable painful stimulation. A high-resolution electroencephalography study. Eur. J. Neurosci. 18 (6) 1692-700). This study tested the hypothesis that alpha ERD before predictable painful stimuli is reduced as an effect of distraction. A visual warning stimulus preceded a laser painful stimulation, which was strictly followed by visual imperative stimuli. In the Pain (control) condition, no task was required after the imperative stimuli. In the Pain + Movement condition, subjects had to perform a movement of the right index finger. In the Pain + Cognition condition, they had to mentally perform an arithmetical task. EEG data were recorded in 10 subjects from 30 electrodes. Artifact-free recordings were spatially enhanced by surface Laplacian transformation. Alpha ERD was computed at three alpha sub-bands according to subjects' individual alpha frequency peak (i.e., about 6-8 Hz, 8-10 Hz, 10-12 Hz). Compared to the control condition, the subjects reported a significantly lower stimulus intensity perception and unpleasantness in the Pain + Movement and Pain + Cognition conditions. In addition, there was a cancellation of the alpha 3 ERD (i.e., about 10-12 Hz) in Pain + Cognition condition and even a generation of a statistically significant alpha 3 ERS in Pain + Movement condition. These effects were maximum over fronto-central midline. These results suggest that distraction during the expectancy of pain is related to a reduced neural desynchronization of fronto-central midline alpha rhythms (i.e., reduced cortical activation) towards an overt hyper-synchronization (cortical idling).     

功能性核磁共振成像在计算机辅助的上肢功能训练治疗脑梗死上肢偏瘫中的应用研究

目的:探讨计算机辅助训练上肢对脑可塑性的可能作用。方法:脑卒中上肢偏瘫患者10例,均进行计算机辅助训练,治疗前后采用偏瘫上肢功能测试-香港版(FTHUE-HK),Fulg-Meyer上肢评定(FMA)及改良Barthel指数量表(MBI)评定上肢运动功能,及患者屈伸腕关节时进行功能核磁共振扫描(fMRI)。结果:治疗6周后,10例患侧的上肢功能评定FTHUE-HK、FMA及MBI评分均较治疗前后患侧上肢功能评定变化明显提高(P0.05)。fMRI扫描示:患者健侧手运动脑功能激活区主要位于对侧初级运动皮质区(SMC)及同侧小脑,患者健手在康复训练后脑激活区增多,包括对侧SMC区及同侧小脑、部分边缘系统;患者治疗前患侧手运动激活区分布广泛,而对侧SMC激活减少,同侧SMC激活增多,另主要还见辅助运动区激活增多;治疗后可见双侧SMC及辅助运动区激活,对侧SMC激活较治疗前增多,另主要还见对侧顶上小叶激活增多。结论:计算机训练可以有效改善脑卒中患者上肢运动功能,诱发大脑皮质功能重塑是其机制的重要组成部分。     

正常人三种模式手指运动时脑激活区域的功能磁共振研究

目的　研究简单动作 (反复连续的手指对指动作 )、随意动作 (抓物体 )和假想动作三种运动模式时 ,脑功能区域的活动机制。方法　利用功能磁共振 (fMRI)影像技术分别摄取 1 0例正常人的利手和非利手在不同运动模式下的双侧脑激活区域 ,再进行机制分析。结果　随意动作时 ,脑同侧激活区的数目多于简单动作 (P <0 .0 5) ,而对侧无明显差异。在简单动作和随意动作中 ,无论利手或非利手 ,主要的激活区为对侧的初级感觉运动皮质 (SM1 ) ,但非利手也可激活同侧少量的SM1。另外 ,脑双侧辅助运动区 (SMA)、前运动区 (PMA) ,对侧顶上小叶 ,同侧小脑也有明显激活 ;偶见基底节激活。假想动作时主要激活额上回、额中回、顶上小叶 ,另见少量扣带回、小脑、脑干、中央旁小叶、基底节处激活。结论　利手的简单动作支配主要在对侧脑SM1 ,而双侧的SM1参与了非利手的简单动作。随意动作属于复杂动作 ,参与动作的区域多于简单动作 ,且双侧SMA均参与 ,可能与双手协调、记忆动作模式的选择、动作顺序的执行有关。假想动作时主要由SMA、PMA支配。该机制对脑卒中的运动训练具有指导意义     

fMRI评价正常老年人腕关节被动运动下脑激活区

目的 用功能磁共振技术观察正常老年人双侧腕关节被动运动时脑区激活情况.方法 对30例正常的右利手老年受试者分别进行双侧腕关节被动运动的功能MR扫描,采用SPM2软件进行数据分析和脑功能区定位.结果 利手(右手)运动主要激活对侧感觉运动皮质、运动前区,双侧辅助运动区、后顶叶及同侧小脑;非利手运动时除激活上述脑区外,还激活了同侧运动感觉区和对侧小脑,且对侧运动前区、双侧辅助运动区和同侧小脑的激活体积明显大于利手腕关节运动.结论 被动运动依赖于大脑皮质和小脑等许多与运动相关的脑功能区的参与;与利手腕关节运动相比,非利手腕关节运动更依赖于对侧PMC、双侧SMA和同侧小脑等运动区.     

The preparation and readiness for voluntary movement: a high-field event-related fMRI study of the Bereitschafts-BOLD response

Activity within motor areas of the cortex begins to increase 1 to 2 s prior to voluntary self-initiated movement (termed the Bereitschaftspotential or readiness potential). There has been much speculation and debate over the precise source of this early premovement activity as it is important for understanding the roles of higher order motor areas in the preparation and readiness for voluntary movement. In this study, we use high-field (3-T) event-related fMRI with high temporal sampling (partial brain volumes every 250 ms) to specifically examine hemodynamic response time courses during the preparation, readiness, and execution of purely self-initiated voluntary movement. Five right-handed healthy volunteers performed a rapid sequential finger-to-thumb movement performed at self-determined times (12-15 trials). Functional images for each trial were temporally aligned and the averaged time series for each subject was iteratively correlated with a canonical hemodynamic response function progressively shifted in time. This analysis method identified areas of activation without constraining hemodynamic response timing. All subjects showed activation within frontal mesial areas, including supplementary motor area (SMA) and cingulate motor areas, as well as activation in left primary sensorimotor areas. The time courses of hemodynamic responses showed a great deal of variability in shape and timing between subjects; however, four subjects clearly showed earlier relative hemodynamic responses within SMA/cingulate motor areas compared with left primary motor areas. These results provide further evidence that the SMA and cingulate motor areas are major contributors to early stage premovement activity and play an important role in the preparation and readiness for voluntary movement.     

Temporal dynamics of alpha and beta rhythms in human SI and SII after galvanic median nerve stimulation. A MEG study

In this MEG study, we investigated cortical alpha/sigma and beta ERD/ERS induced by median nerve stimulation to extend previous evidence on different resonant and oscillatory behavior of SI and SII (NeuroImage 13 [2001] 662). Here, we tested whether simple somatosensory stimulation could induce a distinctive sequence of alpha/sigma and beta ERD/ERS over SII compared to SI. We found that for both alpha/sigma (around 10 Hz) and beta (around 20 Hz) rhythms, the latencies of ERD and ERS were larger in bilateral SII than in contralateral SI. In addition, the peak amplitude of alpha/sigma and beta ERS was smaller in bilateral SII than in contralateral SI. These results indicate a delayed and prolonged activation of SII responses, reflecting a protracted information elaboration possibly related to SII higher order role in the processing of somatosensory information. This temporal dynamics of alpha/sigma and beta rhythms may be related to a sequential activation scheme of SI and SII during the somatosensory information processes. Future studies should evaluate in SII the possible different functional significance of alpha/sigma with respect to beta rhythms during somatosensory processing.     

Cortical alpha rhythms are correlated with body sway during quiet open-eyes standing in athletes: a high-resolution EEG study

Electroencephalographic (EEG; Be-plus Eb-Neuro) and stabilogram (RGM) data were simultaneously recorded in 19 elite karate and 18 fencing athletes and in 10 non-athletes during quiet upright standing at open- and closed-eyes condition in order to investigate the correlation between cortical activity and body sway when the visual inputs are available for balance. Our working hypothesis is that, at difference of non-athletes, athletes are characterized by enhanced cortical information processing as indexed by the amplitude reduction of EEG oscillations at alpha rhythms (about 8-12 Hz) during open- referenced to closed-eyes condition (event-related desynchronization, ERD). Balance during quiet standing was indexed by body "sway area". Correlation between alpha ERD and event-related change of the sway area was computed by a non-parametric test (p<0.05). It was found that alpha ERD (10-12 Hz) is stronger in amplitude in the karate and fencing athletes than in the non-athletes at ventral centro-parietal electrodes of the right hemisphere (p<0.02). Furthermore, there was a statistically significant correlation in the karate athletes between right ventral centro-parietal alpha ERD and body sway area (r=0.61; p<0.008): specifically, the greater the alpha ERD, the greater the percentage reduction of the body sway area when the visual inputs were available. These results suggest that parasylvian alpha ERD of the right hemisphere may reflect the cortical information processing for the balance in elite athletes subjected to a long training for equilibrium control.     

Movement related activity in the high gamma range of the human EEG

Electrocorticographic (ECoG) recordings obtained using intracranially implanted electrodes in epilepsy patients indicate that high gamma band (HGB) activity of sensorimotor cortex is focally increased during voluntary movement. These movement related HGB modulations may play an important role in sensorimotor cortex function. It is however currently not clear to what extent this type of neural activity can be detected using non-invasive electroencephalography (EEG) and how similar HGB responses in healthy human subjects are to those observed in epilepsy patients. Using the same arm reaching task, we have investigated spectral power changes both in intracranial ECoG recordings in epilepsy patients and in non-invasive EEG recordings optimized for detecting HGB activity in healthy subjects. Our results show a common HGB response pattern both in ECoG and EEG recorded above the sensorimotor cortex contralateral to the side of arm movement. In both cases, HGB activity increased around movement onset in the 60-90 Hz range and became most pronounced at reaching movement end. Additionally, we found EEG HGB activity above the frontal midline possibly generated by the anterior supplementary motor area (SMA), a region that was however not covered by the intracranial electrodes used in the present study. In summary, our findings show that HGB activity from human sensorimotor cortex can be non-invasively detected in healthy subjects using EEG, opening a new perspective for investigating the role of high gamma range neuronal activity both in function and dysfunction of the human cortical sensorimotor network.