ABSTRACT
The cerebellum is subdivided into hundreds of discrete modules defined by their connectivity and molecular signatures. Cerebellar compartmentation arises very early in development through the formation of multiple populations of chemically distinct Purkinje cells that migrate in a coordinated fashion to form parasagittal bands of cells. Different Purkinje cell bands are then innervated by discrete subpopulations of cerebellar afferents. Because of its stereotyped and strikingly beautiful organization the cerebellum is an excellent model in which to explore genetic/epigenetic aspects of pattern formation in the central nervous system.
Subject(s)
Cerebellar Cortex/anatomy & histology , Cerebellar Cortex/embryology , Purkinje Cells/cytology , Animals , Neural PathwaysABSTRACT
Most descriptions treat the cerebellum as a uniform structure, and the possibility of important regional heterogeneities in either chemistry or physiology is rarely considered. However, it is now clear that such an assumption is inappropriate. Instead, there is substantial evidence that the cerebellum is composed of hundreds of distinct modules, each with a precise pattern of inputs and outputs, and expressing a range of molecular signatures. By screening a monoclonal antibody library against cerebellar polypeptides we have identified antigens--zebrins--that reveal some of the cerebellum's covert heterogeneity. This article reviews some of these findings, relates them to the patterns of afferent connectivity, and considers some possible mechanisms through which the modular organization may arise.
