Regional differences during cerebellar corticogenesis in the rhesus monkey - abstract

ABSTRACT

This study was undertaken to gain more insight into the complex morphology of the mammalian cerebellum. Investigators of earlier days who attempted to elucidate the fundamental organization of the cerebellum were mainly occupied with the gross morphology of its lobes and fissures, and this closed the eyes initially to other principles of organization. Recent anatomical and electrophysiological studies, however, have increasingly raised support for the concept of a fundamental division of the cerebellum into 4 longitudinal zones with their subdivisions, rather than into transverse lobes and lobules. These zones are based on the compartmentilization of certain afferent and efferent fiber systems of the adult cerebellum. Studies of the development to the cerebellum in a few mammals and man, also revealed the existence of a transient zonal pattern. The latter, however, is based on the temporary clustering of Purkinje cell neuroblasts in the cortical anlage. In the rhesus monkey this period lasts from d.48 until d/80. Horizontal and frontal serial sections of each age were available. The first indication of regional differences is noted on d.50. Between d.54 and d.65 the clusters become increasingly clear and it is possible to distinguish them individually. As development progresses, the clusters are gradually transformed into a Purkinje cell monolayer, which is apparent around d.80. It is highly probable that before it fades away, the embryonic zonal pattern acts as the mould for the permanent adult pattern (AU)