Purchase this article with an account.
Ziv Siman-Tov, Maria Lev, Uri Polat; High processing load of foveal crowding affects binocular summation but can be eliminated by target’s tagging. Journal of Vision 2019;19(10):223c. doi: https://doi.org/10.1167/19.10.223c.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Introduction: In perceptual crowding, a letter that is easily recognized on its own becomes unrecognizable if surrounded by other letters. It’s widely agreed that crowding is robust in the periphery but is almost absent in the fovea. However, recently it was shown (Lev, Yehezkel & Polat, 2014) that crowding occurs in the fovea, when the stimulus is presented for a very short time. Study of crowding in amblyopic eyes (Bonneh, Sagi & Polat, 2003), found that tagging the target with color reduced crowding. In the current study we tested whether tagging the target with color letter reduce crowding in the fovea of subjects with normal vision and whether crowding affects binocular summation. Methods: Letter E with different orientations was briefly presented (40 ms) at the fovea (n=10), either in isolation (single condition) or surrounded by an array of other randomly rotated E letters (crowded condition), with the same or distinct color of the target (pop-out condition). All conditions were mixed by trials. The stimuli were presented via stereoscopic glasses to test binocular summation. Event-related potential (ERPs) were recorded during the experiment. Results: We found a remarkable crowding effect at the fovea, that was significantly reduced for the color target in the pop-out condition. Interestingly, while binocular summation was as expected about 40% it was significantly reduced and almost absent under crowding condition. We found a difference in time and amplitude of some of the ERP components for the crowded conditions, especially in the occipital electrodes. Conclusions: our results are consistent with the notion that the crowding effect produces high processing load and a bottleneck on visual processing, which interferes with other processes such as binocular summation. Interestingly, tagging the target with a distinct color can eliminate or reduce the crowding effect and recover binocular summation.
This PDF is available to Subscribers Only