Cortical excitability in chronic stroke and modulation by training: a TMS study.
BACKGROUND
A possible role for GABA in regulating cortical plasticity after stroke has been proposed.


OBJECTIVE
To investigate changes in intracortical inhibitory and facilitatory circuits in the affected hemisphere more than 6 months after stroke, as well as modulation of excitability by a single training session.


METHODS
A total of 22 patients >6 months after stroke were compared to age- and gender-matched healthy participants. Cortical excitability was assessed by transcranial magnetic stimulation (TMS), including paired-pulse stimulation, before and up to 30 minutes after a single 15-minute session of 1 Hz thumb abduction-adduction movements.


RESULTS
At baseline, TMS showed decreased intracortical inhibition in the affected hemisphere of patients (P = .004) compared to healthy participants. After training a short-lasting decline in motor evoked potentials was observed in both patients (P = .002) and healthy participants (P = .06). Moreover, in healthy participants, inhibitory activity decreased up to 30 minutes after training whereas no significant change was seen in the patients.


CONCLUSIONS
The findings indicate that inhibitory intracortical circuits are less active after stroke, and no change in inhibitory activity is evident after a single training session. This may indicate that intracortical disinhibition is beneficial during recovery and that an impaired capacity for modulation remains in the chronic stage of stroke.
Blicher
Jakob Udby
JU
Hammel Neurorehabilitation and Research Centre, CFIN, Department of Neuroradiology, Aarhus University Hospital, Aarhus, Denmark. jbli@ki.au.dk
Jakobsen
Johannes
J
Andersen
Grethe
G
Nielsen
Jørgen Feldbaek
JF
D000328:Adult; D000368:Aged; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000502:physiology*; D002908:Chronic Disease / Q000534:rehabilitation; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology; D005081:Exercise Therapy / Q000379:methods*; D005260:Female; D006225:Hand / Q000294:innervation / Q000503:physiopathology; D018737:Hand Strength / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D018908:Muscle Weakness / Q000503:physiopathology / Q000534:rehabilitation; D009433:Neural Inhibition / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology*; D020127:Recovery of Function / Q000502:physiology; D020521:Stroke / Q000503:physiopathology; D000071939:Stroke Rehabilitation; D050781:Transcranial Magnetic Stimulation / Q000379:methods*; D005680:gamma-Aminobutyric Acid / Q000502:physiology
D005680:gamma-Aminobutyric Acid