Strategies and mechanisms in nonselective and selective inhibitory motor control.

Motor inhibition was studied in 3 versions of the stop-signal paradigm, with the stop signal requiring inhibition of any response (stop-all), a fixed alternative response (stop-change), or selective inhibition of only 1 of the responses (selective-stop). The lateralized readiness potential was used in Experiment 1 to distinguish between a selective, central, and a global peripheral inhibition mechanism. Inhibition was found to be effected by the central mechanism in the stop-change condition and by the peripheral mechanism in the other conditions. Manipulation of stimulus discriminability in Experiment 2 strongly affected the speed of selective motor inhibition, confirming that such inhibition was achieved by conditionally engaging the peripheral mechanism. These results support the idea that functionally distinct mechanisms and strategies are involved in inhibitory motor control in different situations.