Motor inhibition and response expectancy: A Laplacian ERP study

In between-hand choice reaction time tasks, the motor cortex involved in the required response (contralateral) has been shown to be activated while the motor cortex involved in the non-required response (ipsilateral) has been shown to be inhibited. The aim of the present study was to test the hypothesis that ipsilateral inhibition reflects an active mechanism aimed at preventing errors. To this end, the risk of committing errors in between-hand choice reaction time tasks was manipulated by introducing a response probability bias. The surface Laplacian transforms of electroencephalographic waves recorded over the motor cortices, contralateral and ipsilateral to the responding hand were compared. Results showed that contralateral activation was not modulated by the risk of committing errors while ipsilateral inhibition was sensitive to this risk in a gradual manner: the higher the risk, the stronger the inhibition.