One of the central issues in developmental neurobiology concerns the differentiation of orderly arrangements of cells and their connections. The overall objective of Dr. Casagrande's research is to understand the mechanisms for the development of cellular patterns and connections in the nervous system. The development of layers and connections in the lateral geniculate nucleus (LGN) provides an opportune system for investigation of these mechanisms, since this nucleus, which receives retinal inputs from the two eyes, is precisely organized and many aspects of its organization and development are well-documented. The principal investigator has argued that the development of lamination, per se, in the LGN does not require binocular competition (competition between retinal afferents arising from the two eyes), but that specific functional types of afferents are specified to innervate particular territories. These experiments, using prenatal tree shrews, will examine the degree to which retinal afferents are specified to innervate specific LGN territories by: (1) examining the morphology of individual retinogeniculate axons during the course of early development within the LGN, and (2) examining the morphological development of these axons following monocular enucleation performed prior to retinal innervation of the LGN. The results of this research will provide important and new information on developmental processes involved in laminar formation in the nervous system.
