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Uncovering foveal crowding?

Lev M, Yehezkel O, Polat U - Sci Rep (2014)

Bottom Line: We hypothesized that limiting stimulus availability should decrease object recognition in clutter.Here we show, for the first time, that robust contour interactions exist in the fovea for much larger target-flanker spacing than reported previously: participants overcome crowded conditions for long presentations times but exhibit contour interaction effects for short presentation times.Our results suggest that contemporary models of context modulation should include both time and spatial processing.

View Article: PubMed Central - PubMed

Affiliation: Goldschleger Eye Research Institute, the Sackler Faculty of Medicine, Tel-Aviv University, Tel-Hashomer, Israel.

ABSTRACT
Visual crowding, as context modulation, reduce the ability to recognize objects in clutter, sets a fundamental limit on visual perception and object recognition. It's considered that crowding does not exist in the fovea and extensive efforts explored crowding in the periphery revealed various models that consider several aspects of spatial processing. Studies showed that spatial and temporal crowding are correlated, suggesting a tradeoff between spatial and temporal processing of crowding. We hypothesized that limiting stimulus availability should decrease object recognition in clutter. Here we show, for the first time, that robust contour interactions exist in the fovea for much larger target-flanker spacing than reported previously: participants overcome crowded conditions for long presentations times but exhibit contour interaction effects for short presentation times. Thus, by enabling enough processing time in the fovea, contour interactions can be overcome, enabling object recognition. Our results suggest that contemporary models of context modulation should include both time and spatial processing.

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Contour interaction effect relative to visual acuity for young and presbyopic participants. a) The contour interaction effect (y axis) for the single (uncrowded, red line) and the crowded (blue line) conditions are plotted against the stimulus duration (x axis).The letter size is determined at the threshold of each participant and letter spacing is one letter size. For the presbyopic participants (N = 97 average age = 51 ± 0.64; mean ± se) there was no contour interaction effect for one letter spacing. b) The contour interaction effect (y axis) for one letter spacing (dark blue line, triangles) and 0.4 letter spacing (light blue line, circles) are plotted against the stimulus duration (x axis). The letter size is determined at the threshold for each participant. For new presbyopic participants (N = 41 average age = 50.3 ± 0.13; mean ± se) there was almost a constant contour interaction effect of about 0.5 ETDRS lines (~12%) for 0.4 letter spacing for all time presentation. c) As for b but for young participants (N = 18 average age = 25.4 ± 0.77; mean ± se). There was a robust, and almost constant, contour interaction effect of about 1.5 ETDRS lines (~41%) for 0.4 letter spacing for all presentation times.
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f3: Contour interaction effect relative to visual acuity for young and presbyopic participants. a) The contour interaction effect (y axis) for the single (uncrowded, red line) and the crowded (blue line) conditions are plotted against the stimulus duration (x axis).The letter size is determined at the threshold of each participant and letter spacing is one letter size. For the presbyopic participants (N = 97 average age = 51 ± 0.64; mean ± se) there was no contour interaction effect for one letter spacing. b) The contour interaction effect (y axis) for one letter spacing (dark blue line, triangles) and 0.4 letter spacing (light blue line, circles) are plotted against the stimulus duration (x axis). The letter size is determined at the threshold for each participant. For new presbyopic participants (N = 41 average age = 50.3 ± 0.13; mean ± se) there was almost a constant contour interaction effect of about 0.5 ETDRS lines (~12%) for 0.4 letter spacing for all time presentation. c) As for b but for young participants (N = 18 average age = 25.4 ± 0.77; mean ± se). There was a robust, and almost constant, contour interaction effect of about 1.5 ETDRS lines (~41%) for 0.4 letter spacing for all presentation times.

Mentions: Next, we present data from presbyopic (aging eye) participants whose near vision is blurred due to deterioration of the accommodation power1819. In Figure 3a (N = 97 age 51.091 ± 0.64) we present data for a single letter and for crowded conditions with a target-flanker separation of 1 letter spacing. In Figure 3b (N = 41 age 50.32 ± 0.13) we present data for crowded conditions with a target-flanker separation of 1 letter and 0.4 letter spacing. In Figure 3c we present the results obtained from young participants with normal vision (N = 18, average age 25.4 ± 0.77). Here we used the adaptive method (staircase) that we used previously to measure the crowding effect in the fovea of controls and amblyopic subjects321. The method is similar to that of Flom et al., 19634 whereby the contour interaction is calculated as the difference between the thresholds of a recognized isolated target letter E and the target is embedded in a matrix of E letters.


Uncovering foveal crowding?

Lev M, Yehezkel O, Polat U - Sci Rep (2014)

Contour interaction effect relative to visual acuity for young and presbyopic participants. a) The contour interaction effect (y axis) for the single (uncrowded, red line) and the crowded (blue line) conditions are plotted against the stimulus duration (x axis).The letter size is determined at the threshold of each participant and letter spacing is one letter size. For the presbyopic participants (N = 97 average age = 51 ± 0.64; mean ± se) there was no contour interaction effect for one letter spacing. b) The contour interaction effect (y axis) for one letter spacing (dark blue line, triangles) and 0.4 letter spacing (light blue line, circles) are plotted against the stimulus duration (x axis). The letter size is determined at the threshold for each participant. For new presbyopic participants (N = 41 average age = 50.3 ± 0.13; mean ± se) there was almost a constant contour interaction effect of about 0.5 ETDRS lines (~12%) for 0.4 letter spacing for all time presentation. c) As for b but for young participants (N = 18 average age = 25.4 ± 0.77; mean ± se). There was a robust, and almost constant, contour interaction effect of about 1.5 ETDRS lines (~41%) for 0.4 letter spacing for all presentation times.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3921636&req=5

f3: Contour interaction effect relative to visual acuity for young and presbyopic participants. a) The contour interaction effect (y axis) for the single (uncrowded, red line) and the crowded (blue line) conditions are plotted against the stimulus duration (x axis).The letter size is determined at the threshold of each participant and letter spacing is one letter size. For the presbyopic participants (N = 97 average age = 51 ± 0.64; mean ± se) there was no contour interaction effect for one letter spacing. b) The contour interaction effect (y axis) for one letter spacing (dark blue line, triangles) and 0.4 letter spacing (light blue line, circles) are plotted against the stimulus duration (x axis). The letter size is determined at the threshold for each participant. For new presbyopic participants (N = 41 average age = 50.3 ± 0.13; mean ± se) there was almost a constant contour interaction effect of about 0.5 ETDRS lines (~12%) for 0.4 letter spacing for all time presentation. c) As for b but for young participants (N = 18 average age = 25.4 ± 0.77; mean ± se). There was a robust, and almost constant, contour interaction effect of about 1.5 ETDRS lines (~41%) for 0.4 letter spacing for all presentation times.
Mentions: Next, we present data from presbyopic (aging eye) participants whose near vision is blurred due to deterioration of the accommodation power1819. In Figure 3a (N = 97 age 51.091 ± 0.64) we present data for a single letter and for crowded conditions with a target-flanker separation of 1 letter spacing. In Figure 3b (N = 41 age 50.32 ± 0.13) we present data for crowded conditions with a target-flanker separation of 1 letter and 0.4 letter spacing. In Figure 3c we present the results obtained from young participants with normal vision (N = 18, average age 25.4 ± 0.77). Here we used the adaptive method (staircase) that we used previously to measure the crowding effect in the fovea of controls and amblyopic subjects321. The method is similar to that of Flom et al., 19634 whereby the contour interaction is calculated as the difference between the thresholds of a recognized isolated target letter E and the target is embedded in a matrix of E letters.

Bottom Line: We hypothesized that limiting stimulus availability should decrease object recognition in clutter.Here we show, for the first time, that robust contour interactions exist in the fovea for much larger target-flanker spacing than reported previously: participants overcome crowded conditions for long presentations times but exhibit contour interaction effects for short presentation times.Our results suggest that contemporary models of context modulation should include both time and spatial processing.

View Article: PubMed Central - PubMed

Affiliation: Goldschleger Eye Research Institute, the Sackler Faculty of Medicine, Tel-Aviv University, Tel-Hashomer, Israel.

ABSTRACT
Visual crowding, as context modulation, reduce the ability to recognize objects in clutter, sets a fundamental limit on visual perception and object recognition. It's considered that crowding does not exist in the fovea and extensive efforts explored crowding in the periphery revealed various models that consider several aspects of spatial processing. Studies showed that spatial and temporal crowding are correlated, suggesting a tradeoff between spatial and temporal processing of crowding. We hypothesized that limiting stimulus availability should decrease object recognition in clutter. Here we show, for the first time, that robust contour interactions exist in the fovea for much larger target-flanker spacing than reported previously: participants overcome crowded conditions for long presentations times but exhibit contour interaction effects for short presentation times. Thus, by enabling enough processing time in the fovea, contour interactions can be overcome, enabling object recognition. Our results suggest that contemporary models of context modulation should include both time and spatial processing.

Show MeSH
Related in: MedlinePlus