Fig.1. Activity in cell SIN1 during swimming and non-swimming trials. A. When DP nerve stimulation elicits swimming the membrane potential of each cell SIN 1 hyperpolarizes rapidly and remains hyperpolarized throughout the duration of the swim episode. Swimming in this and all subsequent figures is indicated by rhythmic bursts of actions potential in DP nerves. Note that during swimming cell SIN1 also receives rhythmic inhibitory input. After swimming, the membrane potential of cell SIN1 depolarizes and spiking activity resumes. B. When DP nerve stimulation does not elicit swimming each cell SIN1 hyperpolarizes for only a few seconds. In this and all subsequent figures, swimming is indicated by rhythmic bursts of impulses in the DP nerve. Timing of the DP nerve stimulation is represented by a bar.