Construction of a pattern-generating circuit with neurons of different networks

Abstract

RHYTHMIC motor behaviours are generated within the central nervous system by neuronal circuits called central pattern generators (CPG)¹. Although a CPG can produce several forms of the same behaviour^2–5 and several circuits may interact to generate different behaviours⁶, it is generally assumed that a given CPG consists of a predefined assemblage of neurons that is functionally distinguishable from other circuits. However, recent studies on the stomatogastric nervous system of Crustacea have suggested that CPGs may not be immutable functional entities^7–10. We now report that under an identified neuromodulatory stimulus, the CPG that produces swallowing-like behaviour of the foregut in lobsters is constructed de novo from neurons belonging to other CPGs. Consequently neurons operating independently as members of different circuits may be reconfigured into a new pattern-generating circuit that operates differently from the original circuits. This not only challenges the concept of the CPG being a discrete functional entity, but also demonstrates that a modulatory input can specify an appropriate CPG from a pool of individual neurons of diverse origins.