Figure 1. RIA anatomy and circuit connections. The single RIA axon can be subdivided by physiology and synaptic organization into distinct domains. Shown here are the proximal segment (loop), and the ventral (nrV) and dorsal (nrD) segments of the nerve ring. Convergent sensory input is located exclusively in the loop. Inputs from SMD motor neurons are segregated, such that SMDV innervates the nrV segment, while SMDD innervates nrD. Arrows denote synaptic inputs.