Another clinically significant study assessed the impact of interhemispheric inhibition from the unaffected hemisphere to the affected hemisphere. In normal subjects, the amount of transcallosal inhibition from the “resting” hemisphere to the “active” hemisphere initially decreases and then becomes facilitation just before movement onset (stimulation of one hemisphere leads to a larger response in contralateral stimulation); however, in stroke patients, interhemispheric inhibition remained significant (Murase et al., 2004). Furthermore, the degree of interhemispheric inhibition to the lesioned cortex was correlated with slower performance on a finger-tapping task. Based on these results, the authors postulated that inhibition from the unaffected hemisphere might actually inhibit motor activity from the lesioned hemisphere after stroke.
