Barrow Neurological Institute, St. Joseph's Hospital, Phoenix, Arizona 85013, USA
Address for correspondence: Alan R. Gibson, Barrow Neurological Institute, St. Joseph's Hospital, Phoenix, AZ 85013. Voice: 602-406-3732; fax: 602-406-4172.
agibson{at}chw.edu
Ann. N.Y. Acad. Sci. 978: 219-231 (2002).
The inferior olivary nucleus is the sole source of an entire
afferent system to the cerebellum, the climbing-fiber system.
Inferior olivary neurons are very sensitive to the appropriate
sensory stimuli, such as light contact to the paw. Yet, when
animals move about, olivary cells show little change in discharge
rate. Apparently some mechanism prevents the cells from discharging
to stimuli generated by the animal's own movement. The inferior
olive receives a massive inhibitory input from small cells in
the cerebellar and vestibular nuclei. This article reviews the
results from several experiments that suggest that the inferior
olive is specifically targeted by inhibitory inputs that prevent
responses to stimuli resulting from self-produced movement.
Oscarsson proposed that the inferior olive provides the cerebellum
with information about errors of motor performance and about
spinal reflexes. We argue that it is unlikely that the inferior
olive provides information about movement errors, although the
olive may signal the occurrence of sensory events that are likely
to elicit reflex movements. Another popular theory of climbing-fiber
action argues that the climbing fibers play a role in altering
the strength of the parallel fiber-Purkinje cell synapse. The
cerebellum is important for the formation of classically conditioned
responses, and input generated by the unconditioned stimulus
does provide effective stimulation of olivary neurons. Although
the olive does not generate the unconditioned response, it may
provide the cerebellum with information necessary for the formation
of conditioned responses.
