The cerebrocerebellar system

Abstract

The cerebellum has massive reciprocal interconnections with the cerebral cortex and with cerebral subcortical structures that complement its interconnections with the spinal cord and brainstem. The major cerebrocerebellar link is mediated by the feedforward/afferent corticopontine projections and mossy fi bers emanating from the pontocerebellar projections, and the feedback/efferent cerebellothalamic and thalamocortical projections. These highly arranged connections link sensorimotor, associative and limbic regions of cerebral cortex with the cerebellum and the intervening pontine nuclei and thalamus in a topographically precise manner. The cerebellum also has reciprocal links with the basal ganglia and hypothalamus, and with structures in the limbic circuit. In addition to these mossy fi ber afferents to cerebellum, the inferior olive receives indirect input from motor and associative regions of the cerebral cortex by way of the red nucleus and zona incerta, and it conveys these inputs to cerebellum via climbing fi bers. The cerebrocerebellar pathways are organized into segregated loops of information processing and stand in contrast to the cerebellar cortical architecture that is essentially uniform. Knowledge of cerebrocerebellar circuits is critical to understanding theories of the cerebellar contribution to motor and nonmotor function, and to the diagnosis and management of patients with lesions in these pathways.