Trunk and head displacements stabilized to perform both horizontal and vertical saccadic eye movements

Abstract

Vision is crucial for humans to interact with their surrounding environment, and postural sway is reduced to allow short saccadic eye movements. However, the extent of subtle changes in postural control for horizontal and vertical saccadic eye movements remains unclear. The goal of this study was to investigate the effects of vertical and horizontal saccadic eye movements on head and trunk control in young adults. Fifteen healthy adults (23.4±4.7 years) stood upright in three conditions for 60 s: fixation, horizontal, and vertical guided eye movements. In fixation, participants had to fixate on a stationary target. In both the horizontal and vertical eye movements, the target was presented with a frequency of 0.5 Hz and a visual angle of 11 °. Eye displacement was monitored using a SMI eye tracker (ETG2.0) and trunk and head sway were monitored using infrared markers (Optotrak 3020, NDI). The mean sway amplitude was lower in both directions for eye movements and lowest in the vertical direction compared to the fixation condition. The sway area was also lower in vertical movement than in the fixation condition. We also found that the reduction was greater at head level than at trunk level. The median frequency sway in the anterior-posterior direction was higher in both eye movements than in fixation. Based upon these results, we suggest that to perform short saccadic eye movements, postural sway is more strongly controlled at the head level than at the trunk and in vertical saccadic eye movements than in horizontal movements.

Cervical Proprioception Assessed through Targeted Head Repositioning: Validation of a Clinical Test Based on Optoelectronic Measures

“…Head movements are coupled with eye movements during visual exploration, as they are typically needed to shift the visual field [ 56 ]. From this perspective, there may be differences in how horizontal and vertical head rotations are controlled and exploited for visual exploration and postural control [ 57 ].…”