Coding of goal-directed actions in ventrolateral prefrontal and ventral premotor cortex

Ventrolateral prefrontal (VLPF) cortex is deemed to play a number of motor-related functions, but its contribution to the organization of goal-directed natural actions is still unknown. Here we recorded VLPF and ventral premotor (area F5) neurons of one monkey in a task in which an object or a piece of food elicited two different actions, grasp-to-place or grasp-to-eat, respectively. We analysed 342 VLPF and 222 F5 task-related neurons. Most (45%) of VLPF neurons responded to target presentation, 9% activated only during reaching-grasping, while 29% discharged during both visual presentation and movement execution. Nearly all F5 neurons discharged during motor execution. Fifty-three percent of them also activated during target presentation. Interestingly, although a visual and motor selectivity for the type of target was rare in VLPF single neurons, a clear preference for the object with respect to food emerged at the population level, both during target presentation and motor execution. In contrast, F5 single neurons showed a differential, action goal-dependent, discharge during visual presentation (33%) and during grasping execution (50%). Together with previous findings, these results suggest that goal-directed natural actions might be mainly organized by parieto-premotor circuits, by activating specific motor sequences afforded by the type of target object. In contrast, VLPF might play a role when the action has to be learned through an explicit training process.