Fig. 5.

Tuning the effect of synaptic currents encodes the order of recruitment of V2a interneurons. Blue circles indicate nonrecruited V2a interneurons; red circles indicate recruited V2a interneurons. (A–D) Graphs showing the change in the amplitude with swimming frequency of excitatory and inhibitory currents in a nonrecruited (blue circles) and a recruited (red circles) V2a interneuron. Data in these graphs are from the interneurons in Fig. 4. (E) Linear correlation (R² = 0.43) between the excitatory current amplitude and the relative soma position of V2a interneurons. (F) Graph showing the calculated excitatory inputs of V2a interneurons as a function of the relative soma position. The combination of the input resistance and the excitatory currents in each V2a interneuron predicts the 5-mV cut between nonrecruited and recruited V2a interneurons (dashed line). (G) The calculated excitation correlates well (R² = 0.33) with the measured locomotor-related membrane potential oscillations during swimming.