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Kimberly Meier, Deborah Giaschi, Miriam Spering; Fixation stability during global motion discrimination tasks. Journal of Vision 2018;18(10):1281. doi: https://doi.org/10.1167/18.10.1281.
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Introduction: Beyond the characteristic deficit in visual acuity in one eye, people with unilateral amblyopia (lazy eye) show deficits on a range of visual functions including motion perception at slow speeds. These deficits are usually attributed to the abnormal development of low-level visual motion processing mechanisms. However, unstable fixation has been reported in amblyopia, and may impact motion perception by degrading the input received by direction-selective neurons. Here we ask whether poor performance on slow motion tasks can be accounted for by poor fixation stability. To establish this relation in control observers, we assessed fixation stability in adults with healthy vision during a motion perception task. Methods: Participants (n = 24) performed a global motion direction discrimination task (left/right) with stimuli (600 ms duration) moving at a slow (1 deg/s) or fast (32 deg/s) speed. Dot coherence was controlled with a staircase procedure to obtain coherence thresholds. In a control condition, participants viewed stationary dot patterns. Participants were asked to fixate a central cross throughout the task. Eye movements were recorded with an Eyelink 1000+. Bivariate contour ellipse area and the number of microsaccades on each trial were calculated as indices of stability. Results: Fixation was more stable for the motion discrimination task at either speed, compared to stationary viewing. Participants' overall stability did not predict their coherence thresholds on the motion discrimination task for either speed. Conclusions: Healthy adults show no clear relationship between eye movement stability and global motion coherence thresholds. This suggests fixation instability may not solely account for the motion perception deficits observed in amblyopia.
Meeting abstract presented at VSS 2018
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