Research Description:
Untitled Document
Dr. Edwards has a joint appointment in the Neuroscience Institute as well as the Department of Biology
My research interests concern the integrative properties of single neurons and
neural networks, the effects of growth on those properties, and neural mechanisms
for behavioral choice. These areas are related because the response properties
of neurons gov ern the performance of neural circuits, and the functions of neural
circuits govern the behavior of animals.
Mechanisms of synaptic integration in single neurons. We
are using anatomical imaging, electrophysiology and computer simulations to
understand the integrative properties of an interneuron in crayfish that triggers
the animal's tailflip escape behavior. We have made detailed measurements of
the neuron's shape and membrane properties in small and large crayfish, and
used these measurements to construct computational models of the small and large
cells. We compared the models' responses to simulated synap tic inputs with
the neurons' responses to real synaptic inputs to determine whether the models
account for the physiological changes produced by growth. We have used these
methods to show that growth causes the neuron to become less responsive to brief,
phasic inputs, and more responsive to slower, prolonged inputs. We have also
shown that these changes in the interneuron's response properties during growth
account for the onset of tailflip habituation that occurs as the crayfish grows
larger than 1 inch in length.
Neural Mechanisms of Behavioral Choice. Work in our lab and
elsewhere has shown that different behavior patterns of crayfish are mediated
by discrete neuronal circuits, and that inhibitory interactions occur between
circuits that produce mutually exclusi ve behaviors. For example, the circuit
that mediates backward walking inhibits the tailflip circuit, and vice-versa.
Our modeling studies have shown that mutual inhibition between neural circuits
for incompatible behaviors provides a workable mechanism for adaptive patterns
of behavioral choice. However, inhibition is not the only mode of interaction
because some behaviors can occur concurrently or sequentially. We are now trying
to extend the modeling, behavioral and electrophysiological studies to c over
excitatory interactions between different neural systems, in order to develop
a comprehensive understanding of the neural mechanisms of behavioral choice.
Innervation of Lateral Giant interneuron (light shade) by fourth nerve
afferents (dark shade) in last abdominal ganglion of crayfish.
Recent Publications:
Antonsen,B. & Edwards,D.H. Activity-dependent dye-coupling of primary afferents to the lateral giant neuron in crayfish. (in preparation).
Wood, D.E., Derby, C.D., Edwards, D.H. and Gleeson, R.A. An analysis of the courship display behavior in the blue crab (Calinectes sapidus). Chem. Senses 12: 709.
Musolf,B.E. & Edwards,D.H. Serotonin as a 'borrowed transmitter' in the terminal ganglion of crayfish. (in preparation).
Musolf,B.E. & Edwards,D.H. Activation of uptake of a 'borrowed transmitter' by sensory stimulation in crayfish. (in preparation).
Edwards, D.H. and Herberholz, J. (in press) Crustacean models of aggression, in "The Biology of Aggression", R. Nelson, ed. Oxford Univ. Press.
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