Peripheral maps and synapse elimination in the cerebellum of the rat. I. Representation of peripheral inputs through the climbing fiber pathway in the posterior vermis of the normal adult rat.
The present study gives a detailed description of the functional characteristics and of the topographic distribution of responses, mediated through the climbing fiber pathway and elicited by electrical stimulation of several peripheral inputs, in a circumscribed region of the posterior vermis of the rat cerebellum. Experiments were carried out on normal adult rats under urethane anaesthesia. Purkinje cells (PCs) which responded to the electric stimulation of the contralateral snout, of the ipsilateral and contralateral hindlimb or forepad, and of the tail were recorded in an area extending 1000 microns laterally to the midline in the vermal part of lobules VII and VIII. Using precise micromapping techniques and computer analysis, we located the cells on the map of the unfolded PC layer. Taking into account the mean latency of the responses and the probability of discharge of the PCs, restricted areas of projection were found for the snout, the forepads and the tail. Zones of short-latency responses form compact patches of less than 1 mm2. There was some overlap of projection zones from tail and snout and from forepads and snout. In these zones, there was a convergence of several peripheral inputs on some of the PCs tested. No precise projection of the hindlimbs could be detected in the same lobules. These results fit well with the hypothesis already proposed that the representation of peripheral inputs through the climbing fiber pathway is fractured into a mosaic of patches, which are partly overlapping, and in which remote parts of the body are represented in adjacent areas.
Institut Pasteur, Département des Biotechnologies, Paris, France.
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C
Mulle
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Delhaye-Bouchaud
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Mariani
D000200:Action Potentials; D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D001931:Brain Mapping; D002531:Cerebellum / Q000166:cytology / Q000502:physiology*; D004558:Electric Stimulation; D009475:Neurons, Afferent / Q000502:physiology*; D011689:Purkinje Cells / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D011930:Reaction Time / Q000502:physiology; D012584:Sciatic Nerve / Q000502:physiology