 | NEURONAL MECHANISMS FOR GENERATING LOCOMOTOR ACTIVITY
Copyright © 1998 by the New York Academy of Sciences
description
Annals of the New York Academy of Sciences 860:266-280 (1998)
© 1998 New York Academy of Sciences
Intersegmental Coordination of Swimmeret Movements: Mathematical Models and Neural Circuitsa
BRIAN MULLONEYb,
FRANCES K. SKINNERc,
HISAAKI NAMBA AND
WENDY M. HALL
Section of Neurobiology, Physiology, and Behavior, University of California, Davis, 1 Shields Drive, Davis, California 95616-8519, USA
aThis work was supported by a University of California President's Fellowship to F.K.S. and by National Science Foundation grants IBN 95-14889 and IBN 97-28791 to B.M.
bCorresponding author; e-mail: bcmulloney{at}ucdavis.edu
cPresent address: Playfair Neuroscience Unit, University of Toronto, Toronto, Ont. MST 2S8, Canada.
Swimmerets move periodically through a cycle of power-strokes and return-strokes. Swimmerets on neighboring segments differ in phase by ~25%, and maintain this difference even when the period of the cycle changes from < 1 to >4 Hz. We constructed a minimal cellular model of the segmental pattern-generating circuit which incorporated its essential components, and whose dynamics were like those of the local circuit. Three different intersegmental coordinating units were known to link neighboring ganglia, but their targets are unknown. We constructed different intersegmental circuits which these units might form between neighboring cellular models, and compared their dynamics with the real system. One intersegmental circuit could maintain an ~25% phase difference through a range of periods.
In physiological experiments, we identified three types of intersegmental interneurons that originate in each ganglion and project to its neighbors. These neurons fire bursts at certain parts of the swimmeret cycle in their home ganglion. These three neurons are necessary and sufficient to maintain normal coordination between neighboring segments. Their properties conform to the predictions of the cellular model.
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