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.
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.
Authors: Heidi M Schambra; Isis E Martinez-Hernandez; Kevin J Slane; Amelia K Boehme; Randolph S Marshall; Ronald M Lazar Journal: Restor Neurol Neurosci Date: 2016-09-21 Impact factor: 2.406