A gap junction circuit enhances processing of coincident mechanosensory inputs.
Bottom Line: Modeling approaches have been useful for understanding structurally and dynamically more complex electrical circuits.Therefore, we formulated a simple analytical model with minimal assumptions to obtain insight into the properties of the hub-and-spoke microcircuit motif.Thus, the hub-and-spoke architecture may implement an analog coincidence detector enabling distinct responses to distributed and localized patterns of sensory input.
Affiliation: Cell Biology Division, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK.Show MeSH
Mentions: To test this prediction, we examined the effect of an inactive input on the C. elegans nose touch circuit by either silencing a spoke neuron class or ablating it (Figures 2 and 3). In this circuit, three classes of nose touch mechanosensory neurons—two FLPs, four OLQs, and four CEPs—make gap junctions with a single hub, the RIH interneuron (Figure 2). We showed previously  that active mechanoreceptors facilitate the responses of other sensory neurons in the network to low-threshold stimuli through gap-junction-mediated lateral facilitation. Nose touch stimulation evokes transient calcium increases in all the sensory neurons, as well as a more sustained calcium transient in RIH. Distinct gene products are required cell autonomously in each mechanoreceptor neuron class for sensing touch (Figure 2): the DEG/ENaC channel MEC-10 in the FLPs [9, 13], the TRPV channel OSM-9 in the OLQs [9, 14], and the TRPN channel TRP-4 in the CEPs [15–17]. We thus imaged nose touch responses in animals with either sensory transduction mutations (mec-10, osm-9, or trp-4) that inactivate or ablations that eliminate the same spoke neurons (Figure 3).
Affiliation: Cell Biology Division, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK.