The Motor Control of Hand Movements in the Human Brain: Toward the Definition of a Cortical Representation of Postural Synergies

The control of the many degrees of freedom of the hand through functional modules (hand synergies) has been proposed as a potentially useful model to describe how the hand can maintain postures while being able to rapidly change its configuration to accomplish a wide range of tasks. However, whether and to what extent synergies are actually encoded in motor cortical areas is still debated. A direct encoding of hand synergies is suggested by electrophysiological studies in nonhuman primates, but the evidence in humans resulted, so far, partial and indirect. In this chapter, we review the organization of the brain network that controls hand posture in humans and present preliminary results of a functional Magnetic Resonance Imaging (fMRI) on the encoding of synergies at a cortical level to control hand posture in humans.