The predictive brain: anticipatory control of head direction for the steering of locomotion.

The control of head direction in humans walking along planned circular trajectories was investigated in this study. Five healthy volunteers were asked to walk at a constant speed along circular trajectories in the light and while blindfolded. Head and walking directions were analysed on a real-time basis. Head direction systematically anticipated changes in the direction of locomotion (by about 200 ms). The anticipation interval depended on the curvature of the circle. In the light, head orientation was deviated with respect to the walking direction, toward the inner concavity of the performed trajectory. The results suggest that head direction is controlled on a step-by-step basis in a predictive fashion. A 'go where you look' strategy seems to underlie steering along circular trajectories.