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Jonathan Patrick, Neil Roach, Paul McGraw; Temporal subsampling counteracts motion-related visual acuity loss in the near periphery. Journal of Vision 2015;15(12):285. doi: https://doi.org/10.1167/15.12.285.
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© ARVO (1962-2015); The Authors (2016-present)
While most of us rely on foveal (central) vision for high-resolution tasks, those with macular damage or disease must view the world peripherally. As a step towards making best use of available resolution capacity in such patients, we investigated methods of optimising the presentation of peripheral stimuli in healthy observers. Resolution thresholds were measured for Landolt C targets presented in the near periphery (10 degrees eccentricity). Observers were required to judge the orientation of the target (4 alternatives), which was either static or moving along an isoeccentric path at one of 5 speeds. Consistent with previous findings (Brown, 1972), we found that thresholds rose systematically as a function of target speed, indicating a motion-related loss in visual acuity. In an attempt to disrupt this effect, we subsampled the motion path, removing frames from the stimulus sequence. Interestingly, this manipulation dramatically reduced the impairment of acuity at high speeds, despite reducing the overall information within the stimulus. This effect persisted when the time-average contrast of smooth and sub-sampled paths were equated. Loss of acuity at high speeds is often attributed to shifts in the contrast sensitivity function to lower spatial frequencies (Burr & Ross, 1981). To explore this effect further, we measured contrast sensitivity for a 4c/deg Gabor patch using a similar task, motion paths and range of speeds. For smooth motion, contrast thresholds for orientation identification formed a non-monotonic function of speed, with a marked elevation around 10 deg/s. Subsampled motion paths, however, showed little speed dependence. For physically translating stimuli, the acuity loss for smooth paths and acuity preservation for subsampled paths at high speeds are not easily reconciled with speed-related shifts in contrast sensitivity. Our results suggest that temporal subsampling of visual input can improve peripheral acuity for moving targets.
Meeting abstract presented at VSS 2015
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