Figure 1. Connectivity Diagram of the C. borealis STG and Model Circuit.
In all diagrams colored circles represent neurons, resistor symbols indicate electrical coupling, and arcs terminating in filled circles indicate inhibitory chemical synapses.
(A) The PD and LP cells (red) are conventionally part of the pyloric (fast) circuit; LG and Int1 (blue) are nominally part of the (slow) gastric circuit. The IC neuron (black) has synaptic connections between the pyloric and gastric circuits.
(B–D) Voltage trace of the isolated hub neuron, which has an intrinsic oscillation frequency of 0.57 Hz (B). Half-center oscillators are formed by reciprocally inhibiting fast (C) and slow (D) cells, producing rhythmic frequencies of 0.79 Hz and 0.36 Hz respectively.
(E) Electrically coupling (gel = 5 nS) hn to f2 and s2 results in synchronous firing.
(F) Connectivity diagram of the full model network used in this study.
(G and H) Model-network voltage traces, from top to bottom: f1 (red), f2 (red), hn (black), s2 (blue), s1 (blue). (G) Example of hn oscillating with fast rhythm for a fixed set of synaptic parameters (gsynA = 1.5 nS, gel = 1.5 nS, gsynB = 5 nS). (H) Example of hn oscillating with the slow rhythm (gsynA = 2.5 nS, gel = 2.5 nS, gsynB = 5 nS). Black dashes indicate where membrane voltage is 0 mV.