Switching among functional states by means of neuromodulators in the lobster stomatogastric ganglion

Summary The lobster stomatogastric ganglion contains the central pattern generators (CPGs) for the pyloric and gastric mill rhythms. All of the neurons and their synaptic connections have been identified for each rhythm and serve as the basis for understanding the mechanisms by which chemical neuromodulators are able to alter the functional state of each CPG. Using examples of different amines and peptides, I show how these substances can be found within specific neurons and how their application to the CPG can alter the motor patterns in specific ways. I also discuss what changes in cellular and synaptic properties occur as a result of bath application and particularly in the case of proctolin, how these changes may have behavioral correlates. The various outputs appear to be the result of a functional rewiring of anatomically defined neural circuits and this may be a widespread mechanism for the production of closely-linked but behaviorally distinct movement patterns.