Joint Appointment: Department of Biology
Director of Undergraduate Studies
My research is engaged in “reverse-engineering” the crayfish, to understand how this animal “works” using the same approaches that rival technology companies use to understand each other’s products. Here, however, the “technology” is “alien” and far in advance of anything that people have been able to make. Crayfish are small lobster-like animals that display a wide variety of behaviors that are typically identified with larger animals. Crayfish walk, swim, escape, forage for edible plants, catch prey, dig multichambered burrows for shelter and to raise their young, and establish dominance hierarchies through social interactions, including fighting. The neural circuits that underlie several of these behaviors have been described and, unlike the much more complex nervous systems of vertebrates, these circuits feature large, individually identifiable neurons that make defined synaptic connections with other neurons and body muscles. We use our reverse-engineering approach to understand how these circuits function to produce and control specific behaviors.
We have focused on two behaviors, locomotion (walking) and posture. Neural circuits in the thorax control the legs, and they receive commands from the brain to stand, walk, or turn. This control depends on sensory feedback from leg sensory receptors that report on the position and movement of the leg. We use three approaches to reverse engineer these circuits. First, we record from the leg muscles in freely moving crayfish as we videotape their movements. We can then correlate patterns of muscle activity with the 3-D movements of the limbs and body to determine how patterns of muscle activity produce particular movements. Second, we use AnimatLab, a neuromechanical simulation program that we developed (see www.AnimatLab.com) to reconstruct the neural circuits, muscles and body of the crayfish in a detailed computational model. The model’s ability to simulate crayfish locomotion and postural control tells us whether our current understanding of how the animal works can account for its behavior. Finally, we connect the isolated nervous system and leg stretch receptors to the muscles and stretch receptors of the crayfish model. Experiments with this “hybrid system” allow us to determine the roles of individual interneurons in the control of movement when the sensori-motor feedback loops are intact.
