Effect of Fixational Eye Movement on Signal Processing of Retinal Photoreceptor: A Computational Study

Keiichiro INAGAKI  Takayuki KANNON  Yoshimi KAMIYAMA  Shiro USUI  

Publication
IEICE TRANSACTIONS on Information and Systems   Vol.E103-D   No.7   pp.1753-1759
Publication Date: 2020/07/01
Online ISSN: 1745-1361
DOI: 10.1587/transinf.2019EDP7225
Type of Manuscript: PAPER
Category: Biological Engineering
Keyword: 
visual processing,  information rate,  hyper acuity,  edge enhancement,  spatial smoothing,  

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Summary: 
The eyes are continuously fluctuating during fixation. These fluctuations are called fixational eye movements. Fixational eye movements consist of tremors, microsaccades, and ocular drifts. Fixational eye movements aid our vision by shaping spatial-temporal characteristics. Here, it is known that photoreceptors, the first input layer of the retinal network, have a spatially non-uniform cell alignment called the cone mosaic. The roles of fixational eye movements are being gradually uncovered; however, the effects of the cone mosaic are not considered. Here we constructed a large-scale visual system model to explore the effect of the cone mosaic on the visual signal processing associated with fixational eye movements. The visual system model consisted of a brainstem, eye optics, and photoreceptors. In the simulation, we focused on the roles of fixational eye movements on signal processing with sparse sampling by photoreceptors given their spatially non-uniform mosaic. To analyze quantitatively the effect of fixational eye movements, the capacity of information processing in the simulated photoreceptor responses was evaluated by information rate. We confirmed that the information rate by sparse sampling due to the cone mosaic was increased with fixational eye movements. We also confirmed that the increase of the information rate was derived from the increase of the responses for the edges of objects. These results suggest that visual information is already enhanced at the level of the photoreceptors by fixational eye movements.