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Karl Kopiske, Daniel Koska, Thomas Baumann, Christian Maiwald, Wolfgang Einhäuser; Icy road ahead – gaze during perturbed walking. Journal of Vision 2020;20(11):559. https://doi.org/10.1167/jov.20.11.559.
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© ARVO (1962-2015); The Authors (2016-present)
We can walk effortlessly across flat uniform terrain even when we do not pay much attention to it. However, most natural terrain is far from uniform, and we need visual information to maintain stable gait. Recent advances in mobile eye-tracking technology have made it possible to study the question how real-word terrain affects gaze, and thus sampling of visual information. Studies in natural environments have shown gaze patterns during walking to change depending on terrain. While natural environments are essential for studying walking under realistic conditions, they provide only limited experimental control. Moreover, extreme conditions, such as very slippery surfaces, cannot safely be tested. Typical laboratory setups, in contrast, are far from natural settings for walking. We used a setup consisting of a dual-belt treadmill, a 240° projection screen, floor projection, motion tracking, and mobile eye tracking to investigate eye, head and body movements during perturbed and unperturbed walking in a safe and controlled yet naturalistic environment. To simulate terrain difficulty, we repeatedly induced slipping by rapidly and unpredictably accelerating, on quasi-randomly selected steps, either of the two belts. Subjectively, these perturbations were experienced akin to “slipping on an icy surface.” N=24 participants completed four 5-minute blocks of walking during which slip perturbations of varying speed and frequency occurred, in addition to two blocks of unperturbed walking at beginning and end. We quantified how participants adjusted gait patterns following slips and found persistent distinct gaze patterns to emerge. These gaze patterns scaled with perturbation intensity (slip speed) and were mainly driven by head movements. Interestingly, head and eye movements were neither synchronous nor compensatory to each other, suggesting that both effectors contribute independently to altered gaze patterns during perturbed walking. Our data provide a first step towards experimental quantification of gaze-gait interactions in naturalistic yet fully controlled walking.
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