Analysis of gaze stabilization during stepping and running

Abstract

To investigate the characteristics of the head movements and the mechanisms of gaze, stabilization during walking and running, eye and head movements were recorded in 10 normal subjects and 8 patients with labyrinthine lesions, who repeated stepping (1.OHz) and running (1.5Hz) on the same spot. 1. In normal subjects, head displacements during stepping were limited in the vertical, right-left and anteroposterior directions (0.8, 1.5 and 1.5cm on average, respectively), and the head rotations and the eye movements were also small. During running, the increase in the vertical head displacement (5.5cm on average) induced rhythmical pitching motions of the head and vertical eye movements. 2. In patients with labyrinthine lesions, both the horizontal head displacement and the rotation amplitude became twice as large as those in normal subjects during either locomotion, however, horizontal eye movements did not correspondingly increase. The vertical head displacements during running resembled those of normal subjects, but the amplitude of pitching motion of the head significantly decreased. 3) The spatial stabilization of the head during stepping in normal subjects indicated that walking is a suitable locomotion for gaze stabilization. On the other hand, the head was more unstable during running, however, the pitching motions of the head resulting from vertical head displacements seemed to reduce the concussion of the head and produce vertical compensatory eye movements which maintained the gaze stabilization. 4) In patients with labyrinthine lesions, the horizontal eye movements did not compensate the horizontal head movements during walking and running. Furthermore, since the pitching motions of the head could not be produced rhythmically during running, the vertical body oscillations were directly conducted to the head. The abnormalities of the head movements in addition to the insufficient compensations may cause oscillopsia in these patients. 5) The present study indicated that the head stabilization is essential to maintain the gaze stabilization during walking and running and that the semicircular canals-ocular reflexes act a major role in these mechanisms.