Joint Contribution of Left Dorsal Premotor Cortex and Supramarginal Gyrus to Rapid Action Reprogramming

BACKGROUND The rapid adaptation of actions to changes in the environment is crucial for survival. We previously demonstrated a joint contribution of left dorsal premotor cortex (PMd) and left supramarginal gyrus (SMG) to action reprogramming. However, we did not probe the contribution of PMd to the speed and accuracy of action reprogramming and how the functional relevance of PMd changes in the presence of a dysfunctional SMG. OBJECTIVE This study further dissociated the unique contribution of left PMd and SMG to action reprogramming. Specifically, we tested whether the critical contribution of PMd during action reprogramming depends on the functional integrity of SMG. METHODS Adopting a condition-and-perturb repetitive transcranial magnetic stimulation (rTMS) approach, we first transiently conditioned left SMG with 1 Hz offline rTMS and then perturbed PMd activity with online rTMS whilst human subjects performed a spatially-precued reaction time task. RESULTS Relative to sham rTMS, effective online perturbation of left PMd significantly impaired both the response speed and accuracy in trials that were invalidly pre-cued and required the subject to reprogram the prepared action. Moreover, the disruptive effect of rTMS over left PMd on response speed became stronger after SMG had been conditioned with offline rTMS. CONCLUSIONS These results corroborate the notion that left PMd and SMG jointly contribute to rapid action reprogramming. Moreover, the strong virtual lesion effect observed with rTMS over PMd suggest that this area represents a key node for both the suppression of activation based on the precue and response activation based on the response target.