Network Functions of Electrical Coupling Present in Multiple and Specific Sites in Behavior-Generating Circuits

A thorough understanding of the circuit localization of electrical coupling provides novel insights into its functions. We use a multifunctional rhythm-generating neural network, the Aplysia feeding circuit, as a prime example. This network generates multiple outputs subserving different behavioral needs. Electrical coupling is most commonly observed between ipsilateral neurons of the same type or contralateral homologues. For heterogeneous neurons, it is commonly observed between neurons firing in the same phase of a motor program, but generally not between neurons firing out of phase. Within a single phase, electrical coupling can be present in subgroups of neurons that function as modules. Neurons with more similar activity patterns and functions tend to be more strongly coupled. Electrical coupling also serves to propagate network activity to and from remote circuit elements. Overall, electrical coupling is found throughout the network, but only between specific neurons, making an important contribution to rhythm generation and multifunctionality.