Neural inhibition and interhemispheric connections in two-choice reaction time: a Laplacian ERP study.

In between-hand choice reaction time tasks, the motor cortex involved in the required response is activated while the motor cortex involved in the non-required response is inhibited. Such an inhibition could be implemented actively between the responses defined as possible alternatives by the task instructions or, alternatively, could passively result from some kind of "reciprocal inhibition" between the two motor cortices. The present study addressed this issue. To this end, we compared the surface Laplacian transforms of electroencephalographic (EEG) waves recorded over the contralateral and ipsilateral motor cortices in between-hand and within-hand choice conditions. The dynamics of the recorded EEG activities suggest that inhibition is implemented in a feed-forward manner between the cortical zones controlling the different response alternatives rather than between homologous motor cortical structures.