Ricerc@Sapienza

A major achievement of primates evolution is skilled hand action, that depends on the direct cortico-motoneural system, as well as on the expansion of the parietal lobe. The first is responsible for encoding the dynamic force necessary to grasp and manipulate objects, the second to shape the hand configuration to the physical and geometrical properties of objects. Therefore, the parieto-frontal interplay lays at the core of primates manipulative skills. To characterize the temporal aspects of this recurrent mechanism, we will record neural activity simultaneously from both parietal and premotor cortex of monkeys, while these exert directional hand forces on an isometric joy-stick, so as to move a visual cursor from a central location to different visual targets on a screen. To determine which action parameter is encoded by premotor and parietal neurons, during neural recording, monkeys will be exposed to a new force condition, that will oblige them to change the force output necessary to successfully bring the cursor to the target. This task perturbation will also allow to determine if and how the new learned association between force exerted and visual cursor's motion is encoded by neural activity. Finally, during a 'wash-out' session, the perturbation will be removed, so as to determine whether a memory of the new learned association will remain in neural activity, at the service of predictive control of force during future hand actions. This study is inspired by the consequence of parietal and frontal lesions manipulative skills in humans, that predict that both region participate to the distributed control of hand action, although with different role. It is our hypothesis that while both areas encode force variation over time, premotor cortex has a prominent role in encoding static hand force as well. Parietal cortex can serve as a memory reservoir of the hand dynamics required for object manipulations spanning over time.