Benefits of retinal image motion at the limits of spatial vision

Abstract

Even during fixation, our eyes are constantly in motion, creating an ever-changing signal in each photoreceptor. Neuronal processes can exploit such transient signals to serve spatial vision, but it is not known how our finest visual acuity—one that we use for deciphering small letters or identifying distant faces and objects—is maintained when confronted with such change. We used an adaptive optics scanning laser ophthalmoscope to precisely control the spatiotemporal input on a photoreceptor scale in human observers during a visual discrimination task under conditions with habitual, cancelled or otherwise manipulated retinal image motion. We found that when stimuli moved, acuities were about 25% better than when no motion occurred, regardless of whether that motion was self-induced, a playback of similar motion, or an external simulation. We argue that in our particular experimental condition, the visual system is able to synthesize a higher resolution percept from multiple views of a poorly resolved image, a hypothesis that might extend the current understanding of how fixational eye motion serves high acuity vision.

Evaluation of visual motion perception ability in mice with knockout of the dyslexia candidate susceptibility gene Dcdc2

“…Interestingly, both WTs and Dcdc2 KOs displayed better performance when motion was added to the stimuli, however, Dcdc2 KOs consistently scored lower on percent correct compared with WTs (Figure B,C). This parallels with human findings showing that when motion is added to stimuli acuities were approximately 25% better compared with stimuli without motion . After weeks of moving Gabor testing, subjects advanced to the most difficult task, moving dots.…”

“…This parallels with human findings showing that when motion is added to stimuli acuities were approximately 25% better compared with stimuli without motion. 83 After weeks of moving Gabor testing, subjects advanced to the most difficult task, moving dots. Here, Dcdc2 KOs showed percent correct means that hovered at chance levels while WTs consistently scored above chance after the first week of testing resulting in a significant Genotype effect ( Figure 2D).…”

Suboptimal eye movements for seeing fine details

“…Our results might seem inconsistent with previous reports where complete retinal stabilization resulted in impaired discrimination performance (Ratnam et al, 2017; Rucci et al, 2007). A simple interpolation between the two extremes suggests a monotonic impairment in visual performance with better compensation for FEM.…”

“…Previous research showed that naturally occurring or artificially induced irregular and continuous retinal image drifts help in seeing fine spatial details (Ratnam, Harmening, & Roorda, 2017; Rucci et al, 2007). Likewise, naturally occurring microsaccades or sudden jumps of stimuli are known to counteract visual fading (Costela, McCamy, Macknik, Otero-Millan, & Martinez-Conde, 2013; Martinez-Conde, Otero-Millan, & Macknik, 2013!…”

Spatial summation in the human fovea: the effect of optical aberrations and fixational eye movements

“…However, visual acuity and contrast sensitivity to high-frequency interference fringes-tasks reliant on mechanisms with even finer neural sampling-are generally unaffected when probed with a moving stimulus (Packer & Williams, 1992;Westheimer & McKee, 1975). Moreover, it has been suggested that the visual system may harness the spatiotemporal fluctuations in cone signals produced by eye movements to improve the detection of fine-grained targets (Kuang, Poletti, Victor, & Rucci, 2012;Ratnam, Domdei, Harmening, & Roorda, 2017;Rucci, Iovin, Poletti, & Santini, 2007;Rucci & Victor, 2015). The present findings are consistent with the view that the visual system is equipped with mechanisms capable of disregarding-and in some cases capitalizing on-the retinal image blur introduced by the unsteady eye.…”