Sensory separation in climbing and mossy fiber inputs to cat vestibulocerebellum.

Abstract

Electrical or flash stimulation of the visual pathway evoked in the vestibulocerebellum of barbiturate anesthetized cats, field and unitary potentials characteristic of climbing fiber (CF) activation of Purkinje cells. The latency of the CF field potentials was 11–15 msec in the flocculus and 14–19 msec in the nodulus/ventral uvula. Mossy fiber (MF) related field and unitary responses were not observed following visual stimulation. Conversely, electrical stimulation of the VIIIth nerve evoked in the vestibulocerebellum MF-related field and unitary potentials, exclusively. Despite this dichotomy, the field potentials evoked by visual and vestibular stimulation frequently overlapped within the cerebellar cortex. This overlap was shown at the level of individual Purkinje cells by means of extra- and intracellular recordings which demonstrated vestibulo-visual convergence. These observations indicate that a given sensory modality may reach specific cerebellar areas utilizing only one of the two cerebellar afferent systems. It is concluded that the MF and CF afferent systems, when considered as sensory inputs, can operate as independent information channels.