HEAD STABILITY AND GAZE DURING VERTICAL WHOLE-BODY OSCILLATIONS

To understand head and eye stabilities during upright locomotion, we investigated head and eye movements during vertical whole-body oscillations of various amplitudes (1 to 10 cm) and frequencies (1 to 3 Hz) in both normal subjects (n = 10) and patients with bilateral labyrinthine loss (n = 5). Vertical oscillations produced pitching motions of the head, of which the amplitude was markedly altered by a change in the oscillation frequency or the displacement. Vertical eye movements, being correlated with pitching head movements, were scarcely modified by gaze at 2 and 3 Hz. Acquired bilateral lesions presented deteriorated head stability and physically induced eye movements under stronger stimulations. However, significant increase of head movement upon stepping and suppression of pitching motion upon running, both characteristically found in bilateral lesions, were not reproduced by passive oscillations. Thus, these features during active locomotion may result from imbalance produced by alternate bipedal motions and from adaptation to minimize oscillopsia, respectively. © 1990, SAGE Publications. All rights reserved.