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Michele Rucci, Martina Poletti, Jonathan Victor, Xutao Kuang; Contributions of fixational eye movements to the early encoding of visual information. Journal of Vision 2012;12(9):1123. doi: 10.1167/12.9.1123.
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© ARVO (1962-2015); The Authors (2016-present)
In the periods in between saccades, humans and other species continually perform microscopic eye movements. It is known that these movements prevent fading of the image and enhance vision of high spatial frequencies. However, the impact of microscopic eye movements on the signals impinging onto retinal receptors and on the neural encoding of visual information remains unclear. Here, we examine the spatiotemporal stimulus on the retina of human observers while they freely view pictures of natural scenes. We show that the spectral density of the retinal image during normal intersaccadic fixation differs sharply from that of the external scene: whereas low spatial frequencies predominate in natural images, fixational eye movements redistribute the input power on the retina to yield temporal modulations with uniform spectral density over a wide range of spatial frequencies. This finding links the normal instability of visual fixation to the statistics of the natural world: the resulting equalization of power depends on the joint characteristics of the scene and fixational instability, indicating a form of matching between the statistics of natural images and those of normal eye movements. This spatial whitening of the retinal stimulus implies a reduced sensitivity to predictable input correlations and an enhanced response to luminance discontinuities, outcomes long advocated as fundamental goals of early visual processing. In other terms, our results support a contribution from fixational eye movements to the enhancement of luminance edges in neural representations in the retina and thalamus.
Meeting abstract presented at VSS 2012
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