The Role of Dynamic Gaze Fixations in Human Postural Control

Background: The human postural control system, which controls balance, is constantly taking in sensory input to help maintain balance while allowing one to pay attention to their daily activities. Using visual search tasks, we will be able to understand information relevant to how changes in visual input affects one’s postural control representative of a more real-life scenario. Purpose: With the help eye tracking technology, this study assesses changes in postural control during various visual conditions. Postural control will be measured during such tasks to analyze how it compares to a simple, quiet balancing task. Following Bonnet and Baudry’s Functional Synergist Model, I hypothesize postural sway will be larger during free gaze and precise search tasks compared to a fixed gaze condition. Methodology: 15 healthy, young adults (22 ± 2yrs, 1.69 ± 0.08m, 75.8 ± 17.0kg, 3 men, 12 women) volunteered to participate in this cross-sectional study. Participants were asked to visit the lab and complete standardized assessments while standing quietly on a force plate: 1) a free gaze condition, 2) a fixed gaze condition (representative of the traditional assessments of postural steadiness), and 3) a precise search task. The precise search task was then analyzed in 2 portions: a “pre” section representative of the individual searching for the hidden object, and a “post” section representing fixation once the individual has found the object. During each condition, three 30 second trials were collected, but only 10 seconds were analyzed for each trial due to the aptitude of some participants finding the hidden object in less than 10 seconds during the precise search task. Sway area was calculated from the force plate data and eye tracking data was collected using TobiiPro eye-tracking glasses to confirm task success. Results: Participants displayed 19 ± 21mm of sway area during the free gaze condition, 11 ± 8mm during the fixed gaze condition, 21 ± 31mm while searching for the hidden object, and 9 ± 6mm while fixating on the hidden object. Discussion: These results support my hypothesis that postural sway is larger in both free gaze and the searching portion of the precise search task compared to the fixed gaze condition and the fixation portion of the precise search task. Interestingly, sway area was not larger in the free gaze condition compared to the searching portion of the precise search condition; I anticipated that with a larger area to scan, postural sway would increase due to the unlimited range of visual input, but perhaps participants naturally fixated on a specific area without instruction. Understanding the natural tendencies of participants during the free gaze condition and the precise searching task could help clarify the role of postural control in preventing falls as people tend to scan visual input in daily life