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Kathryn Bonnen, Jonathan S Matthis, Agostino Gibaldi, Martin S Banks, Dennis Levi, Mary Hayhoe; A role for stereopsis in walking over complex terrains. Journal of Vision 2019;19(10):178b. doi: https://doi.org/10.1167/19.10.178b.
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© ARVO (1962-2015); The Authors (2016-present)
When walking across complex terrains, humans gather information about the structure of the path ahead in order to support locomotion. Several studies have established the importance of stereopsis for natural visuomotor control tasks, particularly for tasks involving the arms (e.g., reaching and grasping). We examined the role of stereopsis for walking over complex terrains, a visuomotor control task involving foothold selection and the modulation of gait. Using methods developed by Matthis et al (2018), we recorded the eye and body movements of subjects walking over terrains of varying complexity (pre-designated as flat, medium, or rough). Eight subjects performed the experiment twice, once with their normal or corrected-to-normal vision, and once with a Bangerter foil (0.2, 20/100) over one eye to blur vision and impair stereopsis. In both conditions, subjects adjusted their gaze strategy to accommodate the different difficulties of terrain, allocating more fixations to closer footholds as the terrain became more difficult. The effect of removing stereo-information (using the Bangerter foil) was evident in the medium terrain, where subjects allocated more of their gaze to earlier footholds, indicating that the transition to the rough terrain gaze strategy happens earlier in the absence of stereo-information. Preliminary data from subjects with permanently impaired stereopsis (due to amblyopia and strabismus) indicates a similar strategy, with subjects allocating even more of their gaze to closer footholds in both the medium and rough terrains. The degradation of stereopsis has measurable effects on the gaze strategies used during walking across complex terrains, suggesting that stereopsis is an important source of information for the visuomotor control of locomotion.
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