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.