1. Computerized Visual tracking test (CVT), involves tracking a bright visual target moving horizontally left and right on a computer display in a sinusoidal fashion for several cycles, and at predetermined speeds. The application records (80 Hz) coordinates of both reference and head cursors. Coefficient of determination (COD) will be computed based on total and average residual difference between trajectories of the reference and head cursor motions. A value approaching one equates to excellent gaze performance. This test will be performed in standing and while walking on a treadmill at 0.9 m/s.