Sagittal zonal organization of climbing fibre input to the cerebellar anterior lobe of the ferret.

The organization of climbing fibre input to the cerebellar anterior lobe of the ferret was investigated in barbiturate-anaesthetized animals. Climbing fibre field potentials evoked on electrical stimulation of forelimb and hindlimb nerves were recorded at the cerebellar surface. Based on characteristic latencies of climbing fibre responses and their relative localization along the longitudinal axis of the folia, nine sagittally oriented zones could be distinguished and were tentatively named, from medial to lateral, A, X, B, C1, Cx, C2, C3, D1 and D2. Within the C1, C2 and C3 zones, climbing fibre input from the ipsilateral forelimb was found caudally and from the hindlimb rostrally, while the corresponding topographical representation in the B and D2 zones was medial to lateral. The X, Cx and D1 zones did not receive input from the hindlimb, while input from the forelimb to the A zone was weak. Overall, the sagittal zonal organization of climbing fibre input appears to conform with the compartmentalization of the ferret cerebellum based on the myeloarchitecture of corticonuclear fibres, although the X and Cx zones have not been previously identified. In terms of both general electrophysiological characteristics of input to different zones and intrazonal topographical representation, the organization of climbing fibre input to the ferret cerebellum seems to strongly resemble that in the cat. The findings thus provide evidence of cross-species generality of cerebellar sagittal organization.