[Cerebello-cerebral loop for motor control--controversial issues on extra-cerebellar afferents to the deep cerebellar nuclei].

Intracellular recording was made from dentate nucleus neurons (DNNs) in anesthetized cats, to investigate cerebral inputs to DNNs and their responsible pathways. Stimulation of the medial portion of the contralateral pericruciate cortex most effectively produced EPSPs followed by long-lasting IPSPs in DNNs. Stimulation of the pontine nucleus (PN), the nucleus reticularis tegmenti pontis (NRTP) and the inferior olive (IO) produced monosynaptic EPSPs and polysynaptic IPSPs in DNNs. The results indicate that the excitatory input from the cerebral cortex to DNNs is at least partly relayed via the PN, the NRTP and the IO. Intraaxonal injection of HRP visualized the morphology of mossy fibers from the PN to the dentate nucleus (DN) and the cerebellar cortex. The functional significance of the excitatory inputs from the PN and the NRTP to the DN is discussed in relation to the motor control mechanisms of the cerebellum.