FUNCTIONAL AND ANTIGENIC MAPS IN THE RAT CEREBELLUM - ZEBRIN COMPARTMENTATION AND VIBRISSAL RECEPTIVE-FIELDS IN LOBULE IXA

The mammalian cerebellum is compartmentalized, both structurally and b iochemically, into an array of parasagittal bands. In the adult rat, b ands can be shown by immunocytochemical staining of a Purkinje cell su bset with the monoclonal antibody antizebrin TI. In contrast to the ba nds revealed by the zebrin II distribution, electrophysiological maps of tactile representations show an apparently quite different organiza tion, a patchwork somatotopy of interwoven small receptive fields. We have compared zebrin II compartmentation with the distribution of vibr issal receptive fields in the dorsal face of lobule IXa. Nine adult ra ts were studied. Zebrin II immunocytochemistry revealed a zebrin II+ b and at the midline (P1(+)) and three others (P2(+), P3(+), P4(+)) arra yed laterally, separated by the P1(-), P2(-), and P3(-) bands of unsta ined Purkinje cells. The only significant source of variability was th at P3(-) was sometimes ill defined, making the P3(+) and P4(+) difficu lt to distinguish. Electrophysiological recording in the granular laye r of lobule IXa identified two reproducible vibrissal receptive fields on each side of the midline (V1 and V2), with a third, more laterally , identified occasionally (V3). When receptive field maps were constru cted and aligned with the zebrin II compartment maps from the same ind ividuals, the V1 receptive field was centered on P1(-), V2 on P2(-), a nd V3 on P3(-). However, the receptive fields typically extended beyon d the P- band into the neighboring P+ to each side. Thus there is a si mple, reproducible vibrissal receptive field organization in lobule IX a that bears a constant relationship to the Purkinje cell compartmenta tion revealed by zebrin II immunocytochemistry. The biochemical parcel lation of the cortex may serve to organize the afferent and efferent p rojection topography and thus to align the sensory and motor maps in t he cerebellum. (C) 1994 Wiley-Liss, Inc.