Transplants of Limbic and Neocortex Reveal Mechanisms of Generating Phenotypic Diversity in the Cerebral Cortex

Genetic and environmental factors influence the choices that cells make in expressing specific phenotypic features. We have examined the relative impact of these factors in controlling the fate of neurons comprising specific cerebral cortical areas using fetal tissue transplants/1,2/ and cell cultures of cortical stem cells. The limbic cortical phenotype is assayed in heterotopic and homotopic transplants by two methods: 1) evaluation of the expression of the limbic system-associated membrane protein (LAMP) and 2) mapping of limbic and nonlimbic afferents originating from the host thalamus using DiI labeling of the transplants. Grafts of presumptive limbic or sensorimotor