The pattern of distribution of the local axonal collaterals of Purkinje cells in the intermediate cortex of the anterior lobe and paramedian lobule of the cat cerebellum.

Purkinje cells in the intermediate cortex of the anterior lobe and paramedian lobule of the cat cerebellum were intracellularly injected with horseradish peroxidase. Light microscopic analysis of the distribution patterns of the local collaterals arising from the axons of Purkinje cells in these two cortical areas was carried out. These data suggest that the distribution of the axon collaterals is different in these two areas of the cerebellar cortex. Collaterals arising from the axons of Purkinje cells in the anterior lobe form a highly branched, densely beaded plexus which is restricted to the immediate area of the cell of origin. The axonal ramification is located primarily along the Purkinje cell layer, although a few branches extend into the deep to middle molecular layer. In contrast, collaterals derived from Purkinje cells in the paramedian lobule branch infrequently, and give rise to only a few beaded chains. They extend for great distances, up to 1 mm from the cell of origin. In some cases, collateral branches of paramedian lobule Purkinje cells course into the subcortical white matter to the opposite side of their folium of origin or extend to adjacent folia. These data suggest that the distribution pattern of recurrent collaterals within the cerebellar cortex may not be uniform. In addition, differences in distribution may be correlated with differences in the afferent and efferent organization of the two areas in the cerebellar cortex.