Fig. 7. Rotational positions and velocities following perturbations relative to reference positions and velocities. Points represent mean rotational velocity `errors' normalized to reference velocities and to the time of perturbation (gray vertical lines) as in Fig. 6. Values are means ± 1 S.D. Yaw, pitch and roll Euler angles were calculated relative to a coordinate frame based on the initial movement direction of the animal (see Fig. 3A,C-E). N=11 perturbed trails and N=12 unperturbed reference trials.