9729129 NISENBAUM A fundamental question in developmental neurobiology is how axons from specific neurons in one region of the brain form precise connections with target neurons in another region of the brain. Experiments examining the development of target specificity have revealed two types of mechanisms that contribute to the wiring of neural connections. The first type of mechanism, which occurs during the embryonic and early postnatal period, relies on guidance molecules to direct axonal projections along a path to their correct target region. The second type of mechanism, which takes place later in development, involves activity-dependent events to refine the precise pattern of neuronal connections. Although a great deal is known regarding the development of neuronal circuits within the brain, the development of the connections between the cerebral cortex and the basal ganglia have been largely ignored. The basal ganglia play a critical role in the control of movement and cognitive behaviors. Thus, the formation of precisely patterned connections from the cortex to the primary input structure of the basal ganglia, the striatum, is necessary for the proper functioning of the motor system. The goal of Dr. Nisenbaum's research is to determine when crucial target selection and pattern formation decisions are made during the course of corticostriatal development. The results from these studies will provide a better understanding of the types of mechanisms that are responsible for the precision of corticostriatal connectivity, and also provide insight into how motor systems become organized during development.
