The control of forelimb movements by intermediate cerebellum

This chapter focuses on cerebellar control of forelimb movements. In a series of studies, the functional organization of cerebellar regions contributing to the control of forelimb movements via the rubro- and corticospinal tracts are characterized in the cat. The system consists of the cerebellar cortical C1, C3, and Y zones and their efferent intracerebellar nucleus—the interpositus anterior. Based on analyses of cutaneous and muscle afferent climbing fibre input, of corticonuclear connections, and of controlled limb movements, a modular organization of this cerebellar control system is proposed. Each module consists of a number of cortical microzones, defined by their homogeneous climbing fibre input, and a group of neurones in nucleus interpositus anterior on which these microzones converge. For most climbing fibres, the spatial relationship between cutaneous and muscle afferent input is such that the muscle afferent input originates from muscles that, if activated, would tend to move the cutaneous receptive field of the climbing fibre toward a stimulus applied to the skin.