Fig. 1.

Panel a shows the conventional, cortico-centric, model by which the cerebellar circuitry is described. Afferent inputs, conveyed by CF (climbing fibers) and MF (mossy fibers) terminate predominantly in the cerebellar cortex, with collateral copies to the CN, which are thought to be of lesser importance. The cerebellar cortex processes the signal, which then passes from the Purkinje cells (PC) to the cerebellar nuclei (CN) and out of the cerebellum. Panel b illustrates the nucleo-centric perspective. The primary pathway is for cerebellar afferents to synapse in the CN, where the cerebellar efferents originate. In parallel, afferent copies are sent to the cerebellar cortex, where a complementary inhibitory signal is generated that enters the CN via the corticonuclear pathway and modulates the cerebellar efferent output. Please note that the thickness of the arrows reflects the relative importance of the information flow, not anatomical size or signal strength. Furthermore, blue arrows denote information passing through the CN circuits, without reference to specific cell types