9309691 Chiel In order to survive and reproduce, animals must pursue specific goals while continuously modifying their behavior in response to changing internal and environmental conditions. Over periods of hours or days, animals must choose among different mutually exclusive behaviors, such as feeding or mating. As they engage in a particular behavior over minutes or hours, they must select among different behavioral responses in order to continue to perform that behavior (e.g., rejecting an inedible piece of food in order to continue feeding). They must also rapidly alter their behavioral responses within seconds to cope with changes in the environment (e.g., biting harder on tough food). What are the neural mechanisms underlying the ability of animals to generate adaptive behavior? In order to address this question, the principal investigator proposes to study a behavioral switch in the marine mollusc Aplysia californica. Preliminary results indicate that Aplysia is capable of switching among different behavioral responses as environmental conditions change. Specifically, the animal can switch from ingestive to rejection responses if it attempts to ingest inedible material. The investigator proposes to use intracellular recording from nerve cells in vivo and in vitro (1) to identify and characterize the properties of premotor neurons and interneurons that cause the switch in the timing of the activity of these motor neurons, as well as (2) to identify and characterize the properties of sensory neurons that trigger these different patterns of activity. Using these data, he will (3) simulate and analyze the neural network responsible for the behavioral switch. These three specific aims will allow him to test different hypotheses about the neural organization of a behavioral switch: is it due to dedicated neural circuits, to a distributed neural circuit, or to circuits that have some shared and some distinct neural elements? It will also allow him to develop a more abstract description of behavioral switching, based on concepts from dynamical systems theory.***
