Somatosensory representation of the cerebellar climbing fiber system in the rat.
The climbing fiber responses of 542 Purkinje cells were isolated in the vermal and intermediate zones of lobules II to VI of the rat cerebellum. Mechanical stimulation successfully elicited 53% of the isolated climbing fiber responses, whereas the remaining units were unresponsive to any stimulation employed. Of the units elicited by the stimulation, 34% required cutaneous and 66% required deep stimulation. Some proportion of the representation of each body region required either cutaneous or deep stimulation. The hind-limb had the largest representation and accounted for 55% (160/288) of the units. In contrast, the forelimb was only represented by 10% of the units, the tail by 16%, the face by 11% and the remaining 6% of the units by surface regions of the spine, chest and abdomen. On the basis of their proportional representation of body regions, 3 different cortical areas were distinguished: (1) a medial vermis, which consisted predominantly of unresponsive units; (2) a lateral vermis, which included representations of the extremities, trunk and tail; and (3) the intermediate zone, where the only representation of the face was evident. Within each area, the representations formed a disjunctive pattern of irregularly shaped patches and areas of overlap. In comparison with the climbing fiber organization of the cat, the medial vermal unresponsive zone and the patch-like representations of various body surfaces in the rat were similar to the cat, but the proportional representation of various body surfaces and effective stimulus modality were different, which may reflect morphological and behavioral differences between the species.
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D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D001931:Brain Mapping; D002415:Cats; D002525:Cerebellar Cortex / Q000502:physiology*; D005073:Evoked Potentials, Somatosensory; D008297:Male; D009847:Olivary Nucleus / Q000502:physiology*; D010812:Physical Stimulation; D011689:Purkinje Cells / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D012867:Skin / Q000294:innervation