Effects of saccadic eye movements on postural control stabilization

Sérgio Tosi Rodrigues,Daniela Godoi,José Angelo Barela,Paula Fávaro Polastri,Renato Moraes,Stefane Aline Aguiar

doi:10.1590/s1980-65742013000300012

Abstract

Several structures of the central nervous system share involvement in both ocular and postural control, but the visual mechanisms in postural control are still unclear. There are discrepant evidences on whether saccades would improve or deteriorate stabilization of posture. The purpose of this study was to determine the influence of saccadic eye movements on postural control while standing in different basis of support. Twelve young adults stood upright in wide and narrow stances while performing fixation and saccades of low and high frequencies. Body sway was attenuated during saccades. Trunk anterior-posterior sway and trunk total displacement decreased during saccades compared to fixation; higher sway mean frequency in anterior-posterior direction during saccades was observed. Body sway was reduced in wide compared to narrow stance during high frequency saccades. These results indicate that eye movement improves postural stabilization and this effect is stronger in combination of wide stance-high frequency gaze condition.

Highlights

Integrating posture and search for visual information via eye movements provides crucial support for human activity over its environment
Participants who had to fixate a small light in a dark room, as compared to a completely dark room, largely reduced their spontaneous lateral body oscillations (Paulus, Straube, & Brandt, 1984); situations where the eyes track the light as the head is moving laterally, providing minimum or no retinal shift, suggest that head displacement can be sensed through the amplitude of eye movement, an extraretinal motion perception, not retinal slip (Guerraz & Bronstein, 2008)
The aim of this study was to analyze the effect of horizontal saccades of low and high frequencies on body sway measured during wide and narrow stances

Summary

Introduction

Integrating posture and search for visual information via eye movements provides crucial support for human activity over its environment. Participants who had to fixate a small light in a dark room, as compared to a completely dark room, largely reduced their spontaneous lateral body oscillations (Paulus, Straube, & Brandt, 1984); situations where the eyes track the light as the head is moving laterally, providing minimum or no retinal shift, suggest that head displacement can be sensed through the amplitude of eye movement, an extraretinal motion perception, not retinal slip (Guerraz & Bronstein, 2008) These findings had led to the notion that two different mechanisms subserve visual stabilization of posture: afferent and efferent motion perception. The afferent mechanism is based on characteristics of visual flow (retinal slip); the efferent one is based on either the copy of motor command (efference copy) or the extraocular muscle afferents (re-afferences) consecutive to eye movements (Guerraz & Bronstein, 2008)

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