THE EFFECTS OF EYE MOVEMENTS ON POSTURAL SWAY IN THE ABSENCE OF RETINAL INFORMATION

Date

2023-10-30

Author

Cengiz, Berat Can

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This study aims to investigate the effects of voluntary eye movements (EM) on postural sway experimentally due to the possible effect of extraocular muscle proprioception independent of the effect of retinal information. Thirty healthy volunteers aged 25-37 years participated in the study. Each subject performed eight quiet stance trials, each lasting 200 seconds, in different experimental conditions, the first trial in the light and the later trials in the dark environment while their eyes were open. The second trial was a quiet stance in the dark. The third and fourth trials were performed with sound inputs at two different frequencies (0.0455 and 0.0667 Hz) without eye movements. In the last four experiments, subjects were asked to move their eyes in vertical and horizontal directions periodically at the aforementioned frequencies following the beep sounds in shuffled order. The center of pressure (CoP) signal was estimated through the force platform data collected during the experiments in anteroposterior (CoPx) and mediolateral (CoPy) directions. Simultaneously, eye movements were collected in vertical (EMv) and horizontal (EMh) directions by electrooculography sensors. For each trial, the total path length (PL), the standard deviation of CoP in the anteroposterior (STDx) and mediolateral (STDy) axes, sway area by confidence 95% ellipse (SAC95), and the sweep rate of postural sway area (SASR) were estimated over the CoP signal. The coherence (Coher) and the magnitude (Mcpsd) of the cross-power spectral density function estimates were computed in the frequency domain analyses over EMv versus CoPx and EMh versus CoPy. Repeated measure ANOVA was performed to analyze the effect of manipulation due to vision, sound input, and eye movements for each metric. The coherence and Mcpsd increased significantly in the input frequencies compared to trials without eye movements. Our results revealed an intermittent coherent behavior observed between postural sway and eye movements which varied from subject to subject. PL increased in the dark against the light. SAC95 was significantly larger in the fourth trial compared to the third.

Subject Keywords

Eye movements, Postural sway, Electrooculography, Extraocular muscles, Efference copy

URI

https://hdl.handle.net/11511/105994

Collections

Graduate School of Natural and Applied Sciences, Thesis