Figure 8.

Orientation responses elicited by stepwise changes in concentration. A, Response to upsteps. B, Response to downsteps. In A and B, the black trace shows the trajectory in the absence of a concentration step. The colored traces show the trajectories obtained in response to concentration steps placed at the locations indicated by dots of matching color. The four locations chosen cover a complete cycle of locomotion (dashed box). Vectors indicating the direction of translation (dashed lines) are shown for no concentration step (u), and steps at locations a and c (u_a, and u_c). DS, Dorsal head sweep; VS, ventral head sweep (shaded region).