Modulation of flight by the giant interneurons of the cockroach

Summary

In this paper, I have examined the behavioral functions of feedback loops between the cockroach (Periplaneta americana) giant interneurons (GIs) and the flight thoracic rhythm generator.

• 1. During sequences of flight-like activity, I have recorded from identified giant interneurons from the dorsal (dGIs) or the ventral (vGIs) group and stimulated them either with current pulses or with wind stimuli delivered to the cerci.

• 2. Removal of the dGIs' activity which normally occurs during natural flight reduced both the wingbeat frequency and flight duration, and increased the variability of the wingbeat frequency (Fig. 6). Intracellular rhythmic stimulation of a single dGI during flight increased the wingbeat frequency and the duration of flight (Figs. 7, 8). The wind sensitivity of the dGIs was unchanged during flight compared with at rest (Fig. 2). A single short burst of spikes in a dGI had complex effects on the flight muscle recording but apparently did not reset the flight rhythm (Fig. 9). These results suggest that the rhythmic activation of the dGIs during natural light participates in the control of the wingbeat frequency and the flight duration (Fig. 12).

• 3. In contrast to the dGIs, the vGIs became significantly less sensitive to wind during flight (Fig. 3). Stimulation of one of the vGIs (GI1) with 10 spikes at roughly 180/s during flight evokes immediate cessation of flight (Figs. 10, 11). Given that the vGI activity can stop flight, the inhibition imposed on the ventral group during flight appears to be designed to prevent this group from interfering with the flight program (Fig. 12).