AIY is a set of two interneurons with cell bodies situated in the ventral ganglion behind the excretory duct. AIY is one of the main classes of integrating neuron for the receptors of the amphid sensilla. Processes run up the ventral cord from the cell bodies, forming characteristic structures in the ventral region of the neuropile of the ventral ganglion (e). The processes then run round the nerve ring in the posterior region of the neuropile, meeting and terminating at the dorsal mid-line with a gap junction (b). The main synaptic output from AIY is to AIZ, RIA and RIB. These synapses are mainly in the region of the ventral ganglion and are usually dyadic (a) or triadic (e). There are also a few smaller synapses to AIZ laterally in the nerve ring (c). Synaptic input is predominantly from ASE (*a), AWC (*c), AFD (*a) and AWA (*c). Gap junctions are made to RIM (d). Magnifications: (a, d) x 25500, (b, c, e) x 12750.