Coherence between cortical and muscular activities after subcortical stroke

Background and Purpose-Functional connection between the motor cortex and m uscle can be measured by electroencephalogram-electromyogram (EEG-EMG) cohe rence. To evaluate the functional connection to muscle between contralatera l and ipsilateral motor cortices after pyramidal tract lesions, we investig ated 6 patients with chronic subcortical stroke. Methods-High-resolution EEG and EMG of the hand, forearm, and biceps muscle s were recorded during 3 tonic contraction tasks: (1) elbow flexion, (2) wr ist 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 i psilateral side. EEG-EMG coherence was significantly smaller on the affecte d side for the hand and forearm muscles but not for the biceps muscle. Conclusions-All direct functional connections to muscle after recovered sub cortical stroke come from the contralateral. motor cortex. The different ef fects of the lesion on the proximal and distal muscles appear to be associa ted with the strength of the corticospinal pathway.