Full-body gaze control mechanisms elicited during locomotion: effects of VOR adaptation.

We have previously shown that multiple, interdependent, full- body sensorimotor subsystems aid gaze stabilization during locomotion. In the present study we investigated how the full-body gaze control system responds following exposure to visual-vestibular conflict known to adaptively modify vestibulo-ocular reflex (VOR) function. Subjects (n = 14) walked (6.4 km/h) on a motorized treadmill before and after they were exposed to 0.5X minifying lenses worn for 30 minutes during self-generated sinusoidal vertical head rotations performed while seated. Results indicate that, following the exposure the major changes that subjects showed were to: 1) decrease the amplitude of head pitch and vertical translation of the torso movement with respect to space; 2) increase the amount of knee and ankle flexion during the initial stance phase of the gait cycle. A correlation analysis showed that: 1) changes in the head pitch significantly co-varied with that of the vertical torso translation 2) changes in the knee flexion significantly co-varied with that of the ankle flexion during the initial stance phase of the gait cycle 3) changes in the vertical torso translation significantly co-varied with that of the ankle flexion during the initial stance phase of the gait cycle. Thus we infer that the changes in the magnitude after VOR adaptation in comparison to their pre adaptation responses serve to aid gaze stabilization during locomotion. The significant covariation of the changes between subsystems provides further evidence that the full body contributes to gaze stabilization during locomotion, and its different functional elements are subject to adaptive reorganization following exposure to visual-vestibular conflict.