Cutaneous convergence on to the climbing fibre input to cerebellar Purkyně cells

Abstract

SUMMARY1. In cats anaesthetized with Nembutal, the cutaneous receptive fields of individual cerebellar climbing fibres were assessed by recording the climbing fibre responses of single Purkyn6 cells following controlled mechanical stimulation (air jets, vibration, taps, pressure) of the foot pads of all four limbs and of the hairy skin of the limbs and the body.2. Three major types of cutaneous receptive fields of individual climbing fibres were recognized: (a) restricted fields generally confined to the distal areas of one limb only; (b) circumscribed fields on the distal areas of two to four limbs (discontinuous fields); and (c) widespread continuous fields extending over all or almost all of the body surface. A fourth group appears to receive cutaneous inputs from one limb and sensory input from deeper structures in other limbs.3. Thresholds for tapping of the foot pads were often quite low (< 100,um indentation), and there was no noticeable difference in the distribution of thresholds between the climbing fibres having restricted or more widespread cutaneous receptive fields. Similarly, the latencies of climbing fibre responses evoked by vibration and tapping were in the same ranges for climbing fibres with receptive fields restricted to one limb only and for those having more widespread fields. 4. In regard to location in the anterior lobe of the cerebellum it was found that those climbing fibres receiving inputs only from the ipsilateral forelimb projected to Purkyn6 cells located almost entirely in lobule V, whereas all other climbing fibres with restricted or more widespread receptive fields projected to Purkyn6 cells distributed widely within lobules II to V.

Changes in Excitability of Ascending and Descending Inputs to Cerebellar Climbing Fibers during Locomotion

“…First, within the rostral dorsal accessory olive (the site of relay for climbing fiber paths terminating in the medial C1 zone), descending and ascending projections overlap heavily (Berkley and Worden, 1978;Bull et al, 1990). We found that complex spikes of single Purkinje cells could be evoked by both SR and CP stimulation, providing unequivocal evidence that descending and ascending paths can converge on the same olivary neurons supplying climbing fibers to the relevant region of cortex, as reported previously (Provini et al, 1968;Miller et al, 1969;Leicht et al, 1973;Allen et al, 1974).…”

“…Regardless of their origin, the COCP and SOCP climbing fiber responses share a common final pathway from the olive to the cerebellar cortex (Provini et al, 1968;Miller et al, 1969;Leicht et al, 1973;Rowe, 1977;Andersson and Nyquist, 1983). The pattern of innervation of olivary neurons by inhibitory and excitatory afferents is random, with no obvious preference for one type of terminal targeting intraglomerular or extraglomerular dendrites .…”

Climbing fibre inputs to cerebellar Purkinje cells from trigeminal cutaneous afferents and the SI face area of the cerebral cortex in the cat.

“…Clearly, in the light of the present findings and those of the aforementioned studies (Eccles et al 1972;Leicht et al 1973a), CFs are capable of transmitting very precise information regarding the location and intensity of peripheral sensory events to individual Purkinje cells. The results reported by Oscarsson and his collaborators may be partially attributed to differences in experimental procedure.…”

“…In the lower third of the face, the mandibular skin opposite the canine tooth was a low threshold area, as were the supraorbital sensory hairs in the upper third of the face. Cells having discontinuous receptive skin fields were found less commonly on the face than has been reported for the limbs (Leicht et al 1973a). This may possibly be attributed to the high density of innervation of the face area, and in any case this is consistent with the distribution of receptive fields that has been described for cells in the trigeminal nuclei (Gordon et al 1961; Darian-Smith, Proctor & Ryan, 1963;Rowe & Sessle, 1972).…”

“…Less commonly they were found in the upper third of the face, in the area of the supraorbital tactile hairs. The peripheral field was always confined to skin innervated by one trigeminal branch (see Darian-Smith et al 1965 (Leicht et al 1973a).…”