The Neuronal Basis of the Behavioral Choice between Swimming and Shortening in the Leech: Control Is Not Selectively Exercised at Higher Circuit Levels

Swimming and the whole-body shortening reflex are two incompatible behaviors performed by the medicinal leech Hirudo medicinalis. We set out to examine the neuronal basis of the choice between these behaviors, taking advantage of the fact that the neuronal circuit underlying swimming is relatively w...

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Bibliographic Details
Published in:The Journal of neuroscience 1997-01, Vol.17 (2), p.786-795
Main Authors: Shaw, Brian K, Kristan Jr., William B
Format: Article
Language:English
Subjects:
Action Potentials
Animals
Behavior, Animal
Brain - physiology
Electric Stimulation
Freshwater
Hirudo medicinalis
Interneurons - physiology
Leeches - physiology
Models, Neurological
Motor Neurons - physiology
Muscle Contraction - physiology
Reaction Time
Reflex - physiology
Swimming - physiology
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Summary:Swimming and the whole-body shortening reflex are two incompatible behaviors performed by the medicinal leech Hirudo medicinalis. We set out to examine the neuronal basis of the choice between these behaviors, taking advantage of the fact that the neuronal circuit underlying swimming is relatively well understood. The leech swim circuit is organized hierarchically and contains three interneuronal levels, including two upper levels of "command-like" neurons. We tested the responses of the swim circuit neurons to stimuli that produced shortening, using reduced preparations in which neurophysiological recording could be performed while behaviors were elicited. We found that the majority of the swim circuit neurons, including most of the command-like cells and all of the cells at the highest hierarchical level of the circuit, were excited by stimuli that produced shortening as well as by stimuli that produced swimming. Only a subset of neurons, at levels below the top, were inhibited during shortening; these included one of the command-like cells and an oscillator cell (an interneuron that is part of the central pattern generator for swimming). These results imply that the control of the choice between swimming and shortening is not exercised selectively at the higher levels of the swim circuit.
ISSN:0270-6474
1529-2401
DOI:10.1523/jneurosci.17-02-00786.1997