Purchase this article with an account.
Martina Poletti, Natalya Shelchkova; Perceptual sensitivity to fine detail across the foveola. Journal of Vision 2019;19(10):145b. doi: https://doi.org/10.1167/19.10.145b.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
The foveola covers less than 1% of the visual field. Yet, it is the only retinal region that allows for fine spatial vision. Previous work has shown that fine pattern vision starts to deteriorate already within the foveola. Here we mapped perceptual sensitivity to fine spatial stimuli presented at different foveal locations 20’ away from the center of gaze. To this end, we relied on a combination of techniques allowing for high-resolution recordings of eye position and accurate gaze localization. Observers (n=4) fixated on a marker surrounded by eight boxes (5′×5′) arranged in a circle (20’ radius). Stimuli were presented foveally. Observers were instructed to maintain their gaze at the center of the array throughout the trial. Then, nine probes (7′×2′ bars) were briefly flashed one in each box, and one at the center of gaze. To eliminate confounding factors associated with eye movements, we selected for analysis only trials without microsaccades, in which subjects maintained tight fixation on the central marker. After a blank period, a response cue appeared. Subjects reported the orientation of the probe previously presented at the location indicated by this cue. Performance was assessed at each probe location. Our findings show that fine pattern discrimination was highest at the central location, corresponding to the preferred fixational locus, and, consistently with previous findings, it dropped approximately 20% at the other peripheral locations. Not only subjects were better at discriminating stimuli presented at the preferred fixational locus, but they were also ~250 ms faster in reporting their orientation. Even if the peripheral locations tested were all equidistant from the center of gaze, sensitivity across the foveola was not homogenous. Each subject showed an idiosyncratic distribution of sensitivity, with some foveal locations characterized by higher sensitivity compared to others.
This PDF is available to Subscribers Only