PARASAGITTAL ORGANIZATION OF THE RAT CEREBELLAR CORTEX - DIRECT COMPARISON OF PURKINJE-CELL COMPARTMENTS AND THE ORGANIZATION OF THE SPINOCEREBELLAR PROJECTION

Retrograde and anterograde transport of tracers, electrophysiological recording, somatotopic mapping, and histochemical and immunological techniques have all revealed a parasagittal parcellation of the cerebellar cortex, including its efferent and many of its afferent connections. In order to establish whether the different compartments share a common organizational plan, a systematic comparative analysis of the patterns of parasagittal zonation in the cerebellar cortex of the rat has been undertaken, by using the parasagittal compartmentation of zebrin I+ and zebrin I‐Purkinje cells as revealed by monoclonal antibody Q113 as a reference frame. The distribution of mossy fiber terminals originating from the lower thoracic‐higher lumbar spinal cord was compared to the distribution of zebrin I bands. Three‐dimensional reconstructions from alternate frontal sections processed either for the anterograde transport of tracer or for zebrin I immunoreactivity reveal that the limits of the spinocerebellar terminal fields in the granular layer correlate well with the boundaries of some, but not all, zebrin I compartments in the molecular layer above. This leads to a subdivision of the zebrin I compartments into spinal receiving and spinal nonreceiving portions. In lobules II and VIII, the spinocerebellar terminal fields assume different positions relative to the zebrin I compartments in the ventral compared to the dorsal faces. Thus, each longitudinal compartment may be further divided transversely into subzones, each receiving a specific combination of mossy fiber afferents. The further subdivision of zebrin I compartments by mossy fiber terminal fields increases the resolution of the topography to such a point that anatomical compartment widths become compatible with the width of the microzones and the patches identified by electrophysiological methods. Copyright © 1990 Wiley‐Liss, Inc.