Summary

Grasping behavior has been well studied in both human and non-human primates. Studies have revealed a classic grasping circuit that involves several regions, such as the motor, prefrontal and parietal cortices. However, the functional contribution of the basal ganglia to grasping control is often overlooked. This is surprising because many basal ganglia disorders (e.g. Parkinson's disease) have been experimentally associated with deficits in grasping control. Recent work in our laboratory used fMRI to demonstrate that the caudate, putamen, internal and external segments of the globus pallidus (GPi and GPe, respectively), and subthalamic nucleus (STN) participate in circuits that independently regulate the selection and scaling of parameters important for grasping. These findings provide new evidence that grasping must be considered as a behavior that is processed in both cortical and subcortical structures.

Introduction

Prehension remains one of the most important functions of primate motor systems. The remarkable adaptability and effortlessness with which primates can reach for and grasp objects of variable size, shape and mass has had unequivocal evolutionary importance. Nevertheless, it is widely accepted that even simple reach-to-grasp movements pose considerable challenges for the primate sensorimotor system (Johnson-Frey, 2003). During the prehension of a given object, individuals must use visual (i.e. object distance, direction) and somatosensory information (i.e. joint angle) to transport the hand to the object location via a precisely aimed reaching movement.