The what-decision in manual action: ERPs for free choice versus specified overt goal-related grasping

This study explored the neurophysiological mechanisms underlying the what-decision of planning and execution of an overt goal-related manual action. We aimed to differentiate cerebral activity, by means of event-related potentials (ERPs), between predominantly self-regulated and instructed actions. In a bar-transport task, participants were given free or specified choices about the initial grip and/or final goal. The ERPs for action execution differed between free- and specified-goal conditions, but not between free- and specified-grasp conditions. We found differential activity for the goal specification in mid-frontal, mid-central, and mid-parietal regions from -1100 to -700ms and -500 to 0ms time-locked to grasping and in anterior right regions from -1900 to -1400ms time-locked to movement end. There was no differential activity for grasp specifications. These results indicated that neural activity differed between free and specified actions, but only for goal conditions, suggesting different ways of operation dependent on goal-relatedness. To our knowledge, this was the first study to differentiate cerebral activity and its temporal organization underlying the what-decision involved in overt goal-related actions. Our results support the ideomotor theory by showing that neural processes underlying action preparation and execution depend on the anticipated action goal.