Abstract

C. elegans, with the well-defined connectivity of the 302 neurons in its entire nervous system, offers an opportunity to dissect the function of neural circuits for learning. The “wiring diagram” has facilitated the functional mapping of hard-wired circuits underlying behaviors. We have also identified a second type of circuits, “the invisible wiring diagram”, which regulates olfactory learning, on the basis of peptides, and acts in a way that is largely independent of synaptic connections. Intriguingly, our recent work has uncovered a third type of circuits, “the topographic circuits”, which is based on the subcellular organization of the synapses within individual neuronal processes. These findings together underscore the computational potential of the small C. elegans nervous system in regulating behaviors and experience-dependent plasticity.