Motor-cortex excitabilities change mirror-symmetrically when response tendencies induced by flanking stimuli are cancelled. An ERP-guided TMS study

An important aspect of response selection is the ability to suppress inappropriate response tendencies. Is the inappropriate response tendency cancelled before the activation of the appropriate response, or do these two processes go in parallel? To address this question, we tracked the time courses of excitability of the primary motor hand areas (M1-HAND), by applying transcranial magnetic stimulation as a probe in each trial while healthy volunteers performed a two-choice reaction time task to right- and left-pointing arrows with their right and left index fingers. The central target stimulus was preceded by fl…