Relation between cutaneous receptive fields and muscle afferent input to climbing fibres projecting to the cerebellar C3 zone in the cat.

Inferior olivary cells projecting as climbing fibres to the forelimb area of the cerebellar C3 zone were investigated with respect to their cutaneous and muscle afferent input in barbiturate-anaesthetized cats. Climbing fibre responses were recorded from single cerebellar cortical Purkinje cells on natural stimulation of the skin and on electrical stimulation of nerves to m. biceps brachii, m. triceps brachii and to nine muscles acting as dorsal or palmar flexors of the paw (and, in some cases, the digits). The analysis was focused on the functional organization of convergence between cutaneous and muscle afferents onto single olivary neurons. Cutaneous receptive fields on the dorsal side of the paw and on the digits were generally associated with moderate to strong input from dorsal flexors, but little or no input from palmar flexors or proximal muscles. Receptive fields on the ventral side of the paw and forearm were associated with relatively strong input from biceps and palmar flexors. Climbing fibres with cutaneous receptive fields extending on the ulnar side of the paw and forearm usually received strong input from the triceps and moderate to strong input from dorsal flexors, whereas input from the palmar flexors was weak or lacking. In conclusion, the results indicate that the cutaneous receptive fields in many cases are associated with input from muscles the action of which would tend to move the receptive field towards a stimulus applied to the skin.