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(Stroke. 2001;32:2597.)
© 2001 American Heart Association, Inc.

Original Contributions

Coherence Between Cortical and Muscular Activities After Subcortical Stroke

Tatsuya Mima, MD; Keiichiro Toma, MD; Benjamin Koshy, BS Mark Hallett, MD

From the Human Motor Control Section, Medical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Md.

Reprint requests to Mark Hallett, MD, NIH, NINDS, Medical Neurology Branch, Building 10, Room 5N226, 10 Center Dr, MSC1428, Bethesda, MD 20892-1428. E-mail hallettm{at}ninds.nih.gov

Background and Purpose—— Functional connection between the motor cortex and muscle can be measured by electroencephalogram-electromyogram (EEG-EMG) coherence. To evaluate the functional connection to muscle between contralateral and ipsilateral motor cortices after pyramidal tract lesions, we investigated 6 patients with chronic subcortical stroke.

Methods—— High-resolution EEG and EMG of the hand, forearm, and biceps muscles were recorded during 3 tonic contraction tasks: (1) elbow flexion, (2) wrist extension, and (3) power grip. To evaluate the cortical control of EMG, EEG-EMG coherence was computed.

Results—— EEG-EMG coherence was localized over the contralateral sensorimotor area in all circumstances, and there was no significant coherence at the ipsilateral side. EEG-EMG coherence was significantly smaller on the affected side for the hand and forearm muscles but not for the biceps muscle.

Conclusions—— All direct functional connections to muscle after recovered subcortical stroke come from the contralateral motor cortex. The different effects of the lesion on the proximal and distal muscles appear to be associated with the strength of the corticospinal pathway.

Key Words: electroencephalogram • electromyogram • motor cortex

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