Abstract
Longer stimulus durations aid in resolving fine spatial detail (Graham & Cook, 1937) - an effect partially attributed to fixational eye movements (FEM; Rucci et al., 2007, Anderson et al., 2020). While FEM do not appear to impact acuity at short presentations (6-300 ms; Tulunay-Keesey & Jones, 1976), recent work has shown that stabilizing stimuli on the retina, eliminating the effects of FEM, impedes acuity at longer durations (750 ms; Ratnam et al., 2017). At intermediate durations, the interplay between acuity and stimulus motion on the retina is not well understood. We used an adaptive optics scanning laser ophthalmoscope to stabilize stimuli on the retina at 1 degree from fixation. A 4 AFC tumbling E staircase was used to find the minimum angle of resolution (MAR) for 100, 375 and 750 ms presentations of unstabilized stimuli. The MAR-duration relationship followed an asymptotic shape, improving from 100 ms (mean MAR ± SEM: 1.84 ± 0.17 arcmin) to 375 ms (1.45 ± 0.09) but not to 750 ms (1.48 ± 0.08). Next, performance (% correct) on stabilized and unstabilized stimuli was measured at each duration’s MAR. For stabilized stimuli, we measured performance as a ratio relative to unstabilized performance and found that it degraded with increasing stimulus duration (1.1 ± 0.01, 0.91 ± 0.07, 0.65 ± 0.11 for 100, 375, and 750 ms durations, respectively). These results suggest that retinal stabilization may disrupt the mechanisms by which integration over time enhances visual acuity.
Funding: This project is supported by the Training Program in Vision Science, T32EY007043-44, R00EY027846 & 1R01EY023591.