Insect metamorphosis is a time during which the nervous system is dramatically altered to allow the very different organism which emerges from the larva to behave in new ways appropriate to its new life situation. These pronounced changes in behavior require a striking reorganization of neuronal circuits and the properties of individual cells. Dr. Levine follows the changes in a mechanosensory reflex circuit that mediates a very different behavioral response at different life stages. Using innovative state-of-the-art techniques, he examines the mechanisms by which steroid and peptide hormones direct the formation of new synapses and modifies important cellular events which are reflected in the altered patterns of behavior. Recent findings have led to the conclusion that the adult nervous system is not rigid since adult neurons can undergo morphological changes. Dr. Levine's findings will enhance our understanding of the events underlying neuronal plasticity. Thus, his work holds promise of providing insights into how changes can occur in adult brains, especially with relationship to learning and memory and recovery of function.