Chapter 6 Determinants of axonal and dendritic structure in the superior colliculus

Abstract

Publisher Summary The constraints that govern the conformation of both the axonal arborizations and the dendritic arbors of the central nervous system (CNS) neurons are studied extensively. The rodent superior colliculus (SC) are also used by numerous investigators as a model for studying the development and plasticity of CNS pathways. The dominant input to the superficial SC laminae is that from the retina, and all of the neurons in the superficial SC laminae, the stratum griseum superficial (SGS) and stratum opticum (SO), are exclusively visual. However, when one or both eyes are enucleated at birth, somatosensory axons that would normally terminate in the deep layers (those ventral to the SO) extend into the superficial laminae and make functional contacts with neurons in the SGS and SO. This chapter discusses data that are consistent with the conclusion that the dendrites of at least some tecto-LP cells are reoriented toward the deep laminae after removal of retinal input on the day of birth. They suggest further that retinal ganglion cell axon arbors, which are themselves dorsally directed and achieve this orientation early in development are required for the normal completion of dendritic development that is already underway prior to birth for many of these neurons. The reorientation of dendrites after eye removal is also consistent with the conclusion that these processes are redirected toward sources of residual afferent input.