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Yousef M Shahin, Kimberly Meier, Deborah Giaschi; The effect of visual field location and speed on global motion perception in children and adults. Invest. Ophthalmol. Vis. Sci. 2019;60(9):4375. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Previous work has shown that motion perception matures at an earlier age for fast than for slow speeds on several different tasks. The dorsal stream, which responds well to motion stimuli and is hypothesized to be selectively vulnerable during development, has been reported to show a lower visual field bias. If the slow-speed immaturity reflects protracted development of the dorsal stream, performance should be worse in the lower and central, but not the upper visual field relative to adults.
Children (M age = 8.9 years, n=36) and young adults (M age = 22.6 years, n=36) with healthy vision completed a two-alternative forced-choice global motion direction discrimination task. Coherence thresholds were assessed as a function of speed (1 and 30 deg/s) and signal motion direction (up/down and left/right). Motion stimuli (7.7 x 7.7 deg2; 1.1 dots/deg2) were presented with a centrally-located fixation target, or a fixation target 0.25 deg above or below the stimulus, in order to measure performance in the central, lower, and upper visual field respectively. Each participant completed a total of 12 conditions (2 speeds, 2 directions, 3 locations). An Eyetribe eyetracker was used to monitor fixation in a subset of participants.
For left/right direction discrimination, we found that children had significantly higher coherence thresholds than adults for slow but not fast speeds for the central location (p < 0.001), replicating our previous work. In the upper and lower visual fields, children had significantly higher coherence thresholds than adults for both speeds (p = 0.044). For up/down direction discrimination, children showed similar performance to adults for the central location (p < 0.001). In the upper and lower visual fields, children were significantly immature on the slow, but not fast, motion speeds (p < 0.036 or lower).
Our results are not consistent with exclusive processing of global motion by either dorsal or ventral streams. This work advances our understanding of normal mechanisms of human motion perception, and has implications for understanding the disruption of global motion perception in developmental disorders that is often attributed to dorsal-stream vulnerability.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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