Length and width summation in human vision at different background levels

Vassilev, A.; Zlatkova, Margarita; Mitova, L

doi:10.1007/bf00248877

Cited by 3 publications

(1 citation statement)

References 21 publications

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“…The only difference in the present experimental setup is a higher mean luminance (60 cd0m 2 vs. 14 cd0m 2 ) due to the use of a different CRT display. There is no clear explanation for this selective Ach improvement in critical curvature, but it may be linked to the decrease of spatial summation in orientation selectivity at higher background luminance as suggested by Vassilev et al (1989). This improvement cannot be explained by a relative effect of mean luminance on contrast sensitivity because the contrast sensitivity is expected to be independent of light level in both studies (Rovamo et al, 2001).…”

Section: Wha Beaudot and Kt Mullenmentioning

confidence: 93%

How long range is contour integration in human color vision?

Beaudot

Mullen

2003

Vis Neurosci

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We quantified and compared the effect of element spacing on contour integration between the achromatic (Ach), red-green (RG), and blue-yellow (BY) mechanisms. The task requires the linking of orientation across space to detect a contour in a stimulus composed of randomly oriented Gabor elements (1.5 cpd, s ϭ 0.17 deg), measured using a temporal 2AFC method. A contour of ten elements was pasted into a 10 ϫ 10 cells array, and background elements were randomly positioned within the available cells. The effect of element spacing was investigated by varying the mean interelement distance between two and six times the period of the Gabor elements (l ϭ 0.66 deg) while the total number of elements was fixed. Contour detection was measured as a function of its curvature for jagged contours and for closed contours. At all curvatures, we found that performance for chromatic mechanisms declines more steeply with the increase in element separation than does performance for the achromatic mechanism. Averaged critical element separations were 4.6 6 0.7, 3.6 6 0.4, and 2.9 6 0.2 deg for Ach, BY, and RG mechanisms, respectively. These results suggest that contour integration by the chromatic mechanisms relies more on short-range interactions in comparison to the achromatic mechanism. In a further experiment, we looked at the combined effect of element size and element separation in contour integration for the Ach mechanism. We found that the critical separation decreases linearly with the spatial frequency, from about 5 deg at low spatial frequency (larger elements) to about 1 deg at high spatial frequency (smaller elements) suggesting a scale invariance in contour integration. In both experiments we also found no differences between closed and open jagged contours detection in terms of element separation. The neuroanatomical implications of these findings relatively to area V1 are discussed.

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Section: Wha Beaudot and Kt Mullenmentioning

confidence: 93%

How long range is contour integration in human color vision?

Beaudot

Mullen

2003

Vis Neurosci

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Orientation identification at different background levels: its precision and distortions

Zlatkova

1993

Vision Research

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Resolution acuity and spatial summation of chromatic mechanisms in the peripheral retina

et al. 2021

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Green stimuli are more difficult to detect than red stimuli in the retinal periphery, as reported previously. We examined the spatial characteristics of chromatic mechanisms using stimuli, modulated from an achromatic background to each pole of the “red–green” cardinal axis in DKL space at 20 deg eccentricity. The “blue–yellow” cardinal axis was also studied for comparison. By measuring both grating discrimination at the resolution limit (resolution acuity) and spatial summation, assessed by the Michaelis–Menten function, we demonstrated a marked “red–green” asymmetry. The resolution acuity was worse and spatial summation more extended for “green” compared to “red” stimuli, while showing significant individual variations. Ricco’s area was also measured, but not determined for “green” spots because of the poor small stimuli detection. These results cannot be explained by differences in L- and M-cone numerosity and/or spatial arrangement, but rather have postreceptoral origin, probably at the cortical level.

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Length and width summation in human vision at different background levels

Cited by 3 publications

References 21 publications

How long range is contour integration in human color vision?

How long range is contour integration in human color vision?

Orientation identification at different background levels: its precision and distortions

Resolution acuity and spatial summation of chromatic mechanisms in the peripheral retina

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