Figure 6.

Descending unit activities before spontaneous termination of walking. A, On the top is the bundle recording with the EMG and treadmill movements shown below. The offset time of walking is shown with an arrowhead. B, Activity profiles of a unit isolated from the bundle recording. The rastered spike trains are shown with the superimposition of integrated EMGs and a perioffset time histogram of the unit activity. The inset on the far right shows the location of the recorded bundle on the cross- sectional map of Wiersma (1958) of the circumesophageal commissure. The recording shown in A was obtained when the animal first walked backward and then forward and, finally, stopped walking all spontaneously. This descending unit showed an increased firing rate in 6 of all 11 bouts of walking before its termination regardless of the walking pattern, including straight forward, backward, and curved forward walkings. C, Unit activities aligned to the onset time of walking. No activity change is observed before the behavioral onset.