Stimulation of the dorsal premotor cortex but not of the supplementary motor area impairs performance in a stop-signal task
Being able to stop a movement just begun or about to begin is a distinctive feature of action control. The neural underpinnings of such ability have been widely investigated, postulating a fronto-basal-gaglia inhibitory network. Accumulating evidence speaks for a role of another inhibitory pathway, from the dorsal premotor cortex (PMCd) to the primary motor cortex (M1). However, the clear-cut evidence for the hypothesis that PMCd might be a good candidate for mediating the M1 ability to stop a planned movement is still missing. Here, we stimulated PMCd with single-pulse transcranial magnetic stimulation (TMS) during the response phase of a Stop-signal task (SST), in which healthy volunteers are challenged in stopping a specific movement triggered by a go-signal when a stop-signal is presented after a certain delay. One group received effective TMS over the PMCd, the other group over a control site, the supplementary motor area proper (SMA), both groups received sham TMS. Results showed that when effective TMS was delivered over PMCd during stop trials only, the accuracy was severely affected, leading participants to be less able to inhibit their actions. Our data suggest that PMCd could play a role in the direct control of M1 during voluntary action inhibition.