The Journal of Neuroscience, August 1, 2002, 22(15):6819-6829
The Influence of Somatosensory Cortex on Climbing Fiber Responses
in the Lateral Hemispheres of the Rat Cerebellum after Peripheral
Tactile Stimulation
Ian E.
Brown and
James M.
Bower
Division of Biology, California Institute of Technology, Pasadena,
California 91125
This report describes the temporal relationship between the latency
of responses to peripheral stimulation in primary somatosensory (SI)
cerebral cortex and the timing of climbing fiber inputs to the lateral
hemispheres of the rat cerebellum. Examined in the tactilely responsive
regions of crus IIa in the rat, the results show that SI influences the
timing of both evoked and spontaneous climbing fiber activity in these
cerebellar regions without affecting the rate or probability of complex
spike discharge. By reversibly blocking SI activity, we demonstrate
that the absence of cortical input results in a lengthening of climbing
fiber response latency to peripheral stimuli. Similarly, enhancing the
cortical input by subthreshold electrical stimulation of SI results in
a shortening of climbing fiber response latency. These results provide
a new explanation for the tendency of the inferior olive to
oscillate at 7-12 Hz and is consistent with the hypothesis that the
inferior olive provides the cerebellum information about the timing of cortical computational cycles. Results are discussed in the context of
previous and current hypotheses concerning the physiology and function
of the inferior olive/climbing fiber system and are interpreted to
provide additional evidence of a role for the cerebellum in the tactile
somatosensory system.
Key words:
Purkinje cell; somatosensory; complex spike; cerebellar
cortex; timing; inferior olive
Copyright © 2002 Society for Neuroscience 0270-6474/02/22156819-11$05.00/0
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