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
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Mentions: We formulated a model of a simplified hub-and-spoke circuit (Figure 1A; see also Supplemental Experimental Procedures available online) consisting of a hub interneuron connected to two spoke sensory neurons through electrical synapses (Figure 1A). Since the time course of sensory inputs is substantially slower than the neurons’ electrical time constants, and since C. elegans neurons are characterized by graded potentials rather than action potentials, we focused on the steady state rather than the dynamics of the circuit, reasoning that we could derive analytical expressions for the membrane potentials in each neuron of the model circuit. Based on previous findings , we assumed the gap junctions to be nonrectifying, and we assumed all neurons to be nonspiking and approximately isopotential, consistent with published electrophysiological data . For simplicity, all cells were electrically passive with similar membrane resistance and capacitance. We derived the steady-state membrane potential in the hub interneuron and in the two spoke sensory neurons ( and ) in response to sensory stimulation in terms of five parameters (Figure 1A; Supplemental Experimental Procedures): the relative gap junction strengths of the two spoke connections (α1, α2 > 0), the sensory transduction strengths in the input neurons (β1, β2 > 0), and the receptor reversal potential (Etr > 0).
Affiliation: Cell Biology Division, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK.