Transcranial Magnetic Stimulation to the Frontal Operculum and Supramarginal Gyrus Disrupts Planning of Outcome-Based Hand-Object Interactions

Behavioral data suggest that goals inform the selection of motor commands during planning. We investigated the neural correlates that mediate planning of goal-oriented actions by asking 10 healthy subjects to prepare either a goal-specific movement toward a common object ( a cup), with the intent of grasping-to-pour ( liquid into it) or grasping-to-move ( to another location) the object, or performing a non-object-oriented stimulus-response task ( move a finger). Single-pulse transcranial magnetic stimulation was administered on 50% of trials to the supramarginal gyrus (SMG), anterior intraparietal sulcus, inferior frontal gyrus opercularis (IFGo), and triangularis during motor planning. Stimulation to SMG and IFGo caused a significant delay in planning goal-oriented actions but not responses to an arbitrary stimulus. Despite the delay, movement execution was not affected, suggesting that the motor plan remained intact. Our data implicate the SMG and IFGo in planning goal-oriented hand-object interactions.