Fig. 2. Firing pattern in swim interneuron 1. (A) Lower trace: intracellular recording from Rsint1 during a short episode of swimming. Swimming was initiated by separating the animal's foot from a surface at the first arrow and terminated by returning the surface at the second arrow. Upper trace: a record of the animal's side-to-side swimming movements (upward deflection indicates bending toward the right). (B) Lower trace: bursting activity in Rsint1 at higher gain and on an expanded time base. Insert: the trajectory of membrane voltage at the end of a burst on an expanded scale. Action potentials were truncated by the recording device in this example. Upper trace: a record of the animal's movement. (C) Simultaneous recording of activity in Rsint1 (middle) and Lsint1 (bottom) during a long swimming episode along with the record of swimming movements (top). Note that the spike bursts in these two cells do not overlap.