PARALLEL-PROCESSING OF MECHANOSENSORY INPUTS FROM THE LOCUST OVIPOSITOR BY INTERSEGMENTAL AND LOCAL INTERNEURONS

The neural pathways underlying the processing of signals from locust ( Schistocerca gregaria) ovipositor hairs by different classes of intern eurones are investigated. Spikes in the sensory neurones from these ha irs evoke chemically-mediated, unitary EPSPs with a short and constant latency in six identified non-giant projection interneurones with cel l bodies in the terminal abdominal ganglion. Five of these interneuron es receive direct inputs from the valves ipsilateral to their neuropil ar branches, whereas the other receives direct inputs from valves on b oth sides. The sensory neurone from a single hair makes divergent conn ections with several interneurones and those from different hairs make convergent connections with a given interneurone. The amplitude of th e EPSPs evoked depends on the position of a hair along the proximal-di stal axis of the valve, with sensory neurones from more distal hairs g enerating larger amplitude EPSPs. Deflection of hairs also excites thr ee of the four giant projection interneurones through polysynaptic pat hways and some local interneurones in the terminal abdominal ganglion through monosynaptic connections. Branches of non-giant projection int erneurones, local interneurones, but not those of the giant interneuro nes, overlap the axon terminals of the ovipositor hair afferents in th e terminal abdominal ganglion.