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Michele Rucci, Martina Poletti, Jonathan Victor, Marco Boi; Contributions of Eye Movement Transients to Spatial Vision. Journal of Vision 2015;15(12):211. doi: https://doi.org/10.1167/15.12.211.
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© ARVO (1962-2015); The Authors (2016-present)
Background: Under natural viewing conditions, fast relocations of gaze (saccades) separate brief periods of “fixation”, in which microscopic eye movements continually occur. It is well known that the visual system is highly sensitive to temporal transients, and we have previously shown that fixational instability equalizes the amplitude of the luminance modulations to the retina over a broad range of spatial frequencies (Kuang et al., 2012). However, little attention has been paid to the visual consequences of the natural alternation between macroscopic and microscopic eye movements. How does this recurring sequence of transients affect spatial vision and its dynamics? Methods: We investigated this question by combining three different approaches: spectral analysis of the spatiotemporal input signals to the retina, neural modeling of the responses of retinal ganglion cells, and psychophysical experiments with precise control of retinal stimulation during normal eye movements. Results: We show that saccades and fixational drift yield temporal modulations with highly different spatial distributions. Whereas drift equalizes power across spatial frequency, as previously reported, saccadic transients lead to power at low spatial frequencies. In a model based on the responses of simulated retinal ganglion cells, the transition between these two spectral distributions yields specific predictions regarding the dynamics of contrast sensitivity: fixational eye movements enhance sensitivity to high spatial frequencies, while saccades mainly contribute to vision at low spatial frequencies. Measurements of contrast sensitivity with controlled retinal input show that elimination of saccadic transients and fixational modulations selectively affects sensitivity at low and high spatial frequencies, respectively. Conclusions: These findings suggest that the interplay between saccadic and fixational eye movements results in a coarse-to-fine dynamics of visual perception within each intersaccadic interval.
Meeting abstract presented at VSS 2015
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