Fig. 9: Modeling study of rhythmic generation with network of central pattern generator (CPG).

A CPG model with rhythmic generation. A1 The CPG model was composed of left and right half-center pools, coupled by reciprocal inhibition of commissural interneuron pools (CIN), and driven by cholinergic inputs from the medullar 5-HT neuron pool. This panel was hand-drawn by us. A2 Rhythmic activities of left and right half-centers were generated by excitatory (M3 receptor) and inhibitory (M2&M4) synaptic inputs to 5-HT neuron pool. g_{sye_Exc} = 0.2 μS and g_{sye_Inh} = 0.2 μS were set as control values. Polar plots described coordination of locomotion. The cycle frequency was measured as 0.3 ± 0.03 Hz. B Effect of reducing synaptic conductance on rhythmic activities. B1 Reducing excitatory synaptic conductance gsye_{_Exc} to 25% decreased rhythmic frequency to 0.16 ± 0.06 Hz and disrupted locomotion. B2 Reducing inhibitory synaptic conductance g_{sye_Inh} to 25% increased the rhythmic frequency to 0.38 ± 0.03 Hz with preserved gait stability. C Effect of increasing synaptic conductance on rhythmic activities. C1 Increasing g_{sye_Exc} to 200% increased the rhythmic frequency to 0.33 ± 0.04 Hz with stable gait. C2 Increasing g_{sye_Inh} to 200% reduced rhythmic frequency to 0.23 ± 0.02 Hz with stable gait. Error bars represented SD; paired t-test performed; ∗: P < 0.05; ∗∗: P < 0.01,∗∗∗: P < 0.001, NS: no significant difference. Dash lines in rhythmic bursting represented boundaries within which the recordings were used to calculate frequency of step cycle and polar plots.