Use of Fixation Microsaccades to Increase the Quality of Visible Images in the Foveal Zone

This article addresses the description and analysis of a computer model created by D. S. Lebedev to demonstrate the possibility that fixational microsaccadic eye movements have a positive effect on the perception of small stimuli. The model is based on the suggestion that during fixation of the gaze on the test stimulus under consideration, multiple “neural images” of this stimulus arising as a result of microsaccades are summed in the brain. A series of summed “neural images” corresponds to a sequence of displaced positions of the optical image on the retina. A mechanism for compensating for fixational saccadic microshifts identical to the mechanism ensuring the constancy of spatial perception when macrosaccades occur, i.e., when turning the eyes to examine large objects or scenes, is introduced into the model for precise superimposition of neural images on each other. The author of the model assessed the possibility that the quality of visible images could be improved by increasing the signal-to-noise ratio, which can be achieved using realistic spatiotemporal parameters of test images, neural noise, and eye micromovements, selected on the basis of analysis of the literature. The results of the calculations using the model obtained for the specific retinal parameters and eye movements used showed that the summation mechanism considered here, with saccadic shift compensation, can progressively improve the quality of visible test stimuli as the number of summed neural images increases to about seven or eight, after which there is essentially no further increase in the positive effect. This article discusses the degree of realism of this model based on eye movement recordings from appropriate experiments.