Vestibular Labyrinth Contributions to Human Whole-Body Motion Discrimination

To assess the contributions of the vestibular system to whole-body motion discrimination in the dark, we measured direction recognition thresholds as a function of frequency for yaw rotation, superior-inferior translation (z-translation), interaural translation (y-translation), and roll tilt for 14 normal subjects and for 3 patients following total bilateral vestibular ablation. The patients had significantly higher average threshold measurements than normal (p < 0.01) for yaw rotation (depending upon frequency, 5.4 x to 15.7 x greater), z-translation (8.3 x to 56.8 x greater), y-translation (1.7 x to 4.5 x greater), and roll tilt (1.3 x to 3.0 x greater)-establishing the predominant contributions of the vestibular system for these motions in the dark.