Selective inhibition of movement.

In studies of volitional inhibition, successful task performance usually requires the prevention of all movement. In reality, movements are selectively prevented in the presence of global motor output. The aim of this study was to investigate the ability to prevent one movement while concurrently executing another, referred to as selective inhibition. In two experiments, participants released switches with either their index and middle fingers (unimanual) or their left and right index fingers (bimanual) to stop two moving indicators at a fixed target (Go trials). Stop trials occurred when either one or both indicators automatically stopped before reaching the target, signaling that prevention of the prepared movement was required. Stop All and selective Stop trials were randomly interspersed among more frequently occurring Go trials. We found that selective inhibition is harder to perform than nonselective inhibition, for both unimanual and bimanual task contexts. During selective inhibition trials, lift time of the responding digit was delayed in both experiments by <or=100 ms, demonstrating the generality of the result. A nonselective neural inhibitory pathway may temporarily "brake" the required response, followed by selective excitation of the to-be-moved digit's cortical representation. After selective inhibition trials, there were persistent asynchronies between finger lift times of subsequent Go trials. The persistent effects reflect the behavioral consequences of nonspecific neural inhibition combined with selective neural disinhibition.