Corticocortical coupling in chronic stroke: its relevance to recovery.
BACKGROUND
The mechanisms behind motor recovery from stroke are not clearly understood. Functional imaging studies have demonstrated task-related brain activation in several motor areas, but few studies have attempted to correlate this with stroke outcome. Moreover, these studies have focused on how motor areas may individually contribute to compensation. Here, the authors investigate whether different cortical areas interact to form dynamic assemblies that may then compensate for disability.


METHODS
The authors investigated corticocortical coherence in 16 healthy subjects and 25 patients with chronic stroke involving one cerebral hemisphere and having varying degrees of motor recovery. Scalp EEG was recorded at rest and while right-handed subjects performed a unimanual grip task. The degree of functional recovery after stroke was assessed using a range of outcome measures.


RESULTS
Compared with healthy subjects, hand-related asymmetries in task-related EEG-EEG coherence were increased between mesial and lateral frontal regions of the affected hemisphere, over mesial frontal regions, and over lateral frontal areas of the unaffected hemisphere when patients with stroke gripped with their affected hand. Mesial hand-related asymmetries in task-related power and coherence were negatively correlated with recovery.


CONCLUSIONS
Increases in task-related coupling between cortical areas may dynamically compensate for brain damage after stroke. Some of this increased coupling, particularly that over mesial frontal areas, decreases as patients make a functional recovery.
Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology and National Hospital for Neurology and Neurosurgery, London, UK.
L H A
LH
Strens
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P
Asselman
A
A
Pogosyan
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C
Loukas
A J
AJ
Thompson
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P
Brown
D000328:Adult; D000368:Aged; D002540:Cerebral Cortex / Q000503:physiopathology*; D002908:Chronic Disease; D004292:Dominance, Cerebral; D004569:Electroencephalography; D004576:Electromyography; D005260:Female; D005625:Frontal Lobe / Q000503:physiopathology; D018737:Hand Strength; D006801:Humans; D020244:Infarction, Middle Cerebral Artery / Q000150:complications / Q000503:physiopathology / Q000534:rehabilitation; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology; D009415:Nerve Net / Q000503:physiopathology*; D009473:Neuronal Plasticity; D010291:Paresis / Q000209:etiology / Q000503:physiopathology* / Q000534:rehabilitation; D011597:Psychomotor Performance; D020127:Recovery of Function; D020521:Stroke / Q000150:complications / Q000503:physiopathology*; D000071939:Stroke Rehabilitation; D016896:Treatment Outcome