Localization of cutaneously elicited climbing fiber responses in lobule V of the monkey cerebellum.

The somatotopic organization of climbing fibers (CF) elicited by natural stimulation was determined for the intermediate zone of lobule V of Macaca fascicularis. In monkeys anesthetized with sodium pentobarbital, extracellular recordings of single Purkinje cells with CF responses were evaluated by gentle taps to the body and by computer-controlled punctate stimuli. Of the 311 Purkinje cells studied, 53% had CF responses elicited by cutaneous stimulation whereas the remaining cells were unresponsive. The entire ipsilateral, dorsal surface of the forelimb, face, and the oral cavity were represented in the intermediate zone. The topographic organization consisted of three 1.5-3 mm wide parasagittal bands of cells: a forelimb band medially, then a face band, and an unresponsive zone laterally. Most receptive fields in the forelimb band involved portions of the wrist, hand, and digits, although shoulder, arm, and forearm were also represented. The receptive fields of the hand usually included more than 1 digit and only a few fields contained the thumb. Most responses in the face band were elicited by stimulation of areas innervated by the mandibular division of the trigeminal nerve, although some responses were produced by stimulating areas related to the ophthalmic and maxillary divisions and to the anterior cutaneous nerve. Cells with similar receptive fields tended to be grouped together. The somatotopic CF organization of the monkey differed in many ways from the arrangement in the cat.