Neuromodulation and Motor Pattern Generation in the Crustacean Stomatogastric Nervous System
Neuromodulation is critically important to the functioning of nervous systems, yet it is not included in most descriptions of neuronal circuits. Neuromodulation has been extensively studied in the stomatogastric nervous system of decapod Crustacea. Here it has been shown that neuromodulatory inputs to central pattern generator circuits play four key roles. 1) They can initiate and maintain rhythmic neuronal activity. 2) They allow a single, anatomically defined circuit to produce many different outputs. 3) They can cause cells to switch their activity from one neuronal circuit to another. 4) They can reconfigure entire networks so that previously independent circuits can function together in a coordinated fashion. Thus, the classical synaptic connections of a neuronal circuit are not enough to explain the behavioural output of that circuit; neuromodulation can alter the output by affecting cellular and synaptic properties. This imparts a greater flexibility upon nervous systems than can be attained through simple excitatory/inhibitory interactions.
KeywordsSerotonin Acetylcholine Cholecystokinin FMRFamide Proglumide
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