The cerebrocerebellar system.

If there is a cerebellar contribution to nonmotor function, particularly to cognitive abilities and affective states, then there must be corresponding anatomic substrates that support this. The cerebellum is strongly interconnected with the cerebral hemispheres in both feedforward (cerebral hemispheres to cerebellum) and feedback directions. This relationship has long been recognized, particularly with respect to the motor and sensory cortices. Investigations performed over the last decade however, have demonstrated for the first time the organization and strength of the connections that link the cerebellum with areas of the cerebral cortex known to be concerned with higher order behavior rather than with motor control. The feedforward projections from these higher order areas, namely the associative and paralimbic cortices, seem to be matched, at least in the limited but definite demonstrations to date, by cerebellar projections back to these same areas. These observations are important because they are congruent with the notion that cognitive functions are distributed among multiple cortical and subcortical nodes, each of which functions in concert but in a unique manner to produce an ultimate behavior pattern. This chapter describes the neural circuitry postulated to subserve the cerebellar contribution to nonmotor processing, particularly cognitive and affective modulation, and discusses the theoretical implications of these anatomic findings.