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Marco Boi, Martina Poletti, Michele Rucci; Perceptual consequences of temporal modulations resulting from eye movements. Journal of Vision 2013;13(9):1095. doi: 10.1167/13.9.1095.
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During normal viewing, saccades alternate with fixational eye movements, yielding complex patterns of temporal modulations in the retinal input. Although it is well known that the visual system is highly sensitive to temporal changes, it is unclear how the modulations resulting from eye movements affect spatial vision. To address this question, we measured contrast thresholds in a forced choice task in which subjects reported the orientation of a grating (±45o) during natural post-saccadic fixation. The grating was either at low (1 cpd) or high spatial frequencies (10 cpd) and appeared while the saccade was in flight. To examine the effects of saccade transients, we first substituted the normal abrupt input change caused by saccades (normal condition) with a slow increment in contrast (1.5 s) starting at the very end of the saccade (no-transient condition). Elimination of the saccadic transient impaired sensitivity at low spatial frequency, but had no effect at high
spatial frequency. We then examined how sensitivity evolves during the course of normal post-saccadic fixation by changing the duration of the post-saccadic presentation (100 ms or 800 ms). To replicate the visual input that occurs during natural viewing, gratings were embedded in a noise field with a 1/f spectrum (f spatial frequency) which covered the entire display. Sensitivity for low spatial frequencies did not change during the course of fixation, whereas sensitivity to high spatial frequencies increased significantly. In agreement with previous results (Rucci et al., 2007), elimination of the temporal modulations resulting from fixational eye movements yielded a 20% decrease in sensitivity at high spatial frequencies and no change at low spatial frequency. These findings indicate that the interplay between macroscopic and microscopic eye movements contribute to a-coarse-to-fine dynamics of visual processing during natural fixation.
Meeting abstract presented at VSS 2013
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