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Donald
H. Edwards
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Research |
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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.
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Ph.D.,