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Edwards, Don H.

Regents' Professor
Office: 825 Petit Science Center
Phone: (404) 413-5394
Email: dedwards@gsu.edu
Website: http://www2.gsu.edu/~biodhe/

Biographical Information

Ph.D. Yale University 1976
Postdoctoral Training: Stanford University and University of California-Davis
Joint Appointment: Department of Biology
Director of Undergraduate Studies

Research Description:

I am interested in how neural circuits control an animal’s body to enable it to produce adaptive patterns of behavior.  My students and I study this in the crayfish, a freshwater decapod crustacean that displays 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 a “reverse-engineering” approach to understand how these circuits function to produce and control specific behaviors.   

We have focused recently 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 study 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 crayfish nervous system and leg stretch receptors to the model muscles and stretch receptors of the crayfish model. Motor activity from the nervous system causes the model legs to move, and these movements excite sensory afferents to provide feedback to the nervous system.  Experiments with this closed loop “hybrid system” allow us to determine the role of sensory feedback in the control of movement when the sensori-motor feedback loops are intact.