Individual differences in chromatic (red/green) contrast sensitivity are constrained by the relative number of L- versus M-cones in the eye

Gunther, Karen L.; Dobkins, Karen R.

doi:10.1016/s0042-6989(02)00043-3

Cited by 49 publications

(41 citation statements)

References 66 publications

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“…Because here the log contrast sensitivity data did not conform to normality (as is usually the case, see Gunther & Dobkins, 2002), non-parametric Mann-Whitney tests were used for this analysis.…”

Section: Discussionmentioning

confidence: 99%

Spatial Contrast Sensitivity in Adolescents with Autism Spectrum Disorders

Koh

Milne

Dobkins

2010

J Autism Dev Disord

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Adolescents with Autism Spectrum Disorders (ASD) and typically developing (TD) controls underwent a rigorous psychophysical assessment that measured contrast sensitivity to seven spatial frequencies (0.5 to 20 cycles/degree). A contrast sensitivity function (CSF) was then fitted for each participant, from which four measures were obtained: visual acuity, peak spatial frequency, peak contrast sensitivity, and contrast sensitivity at a low spatial frequency. There were no group differences on any of the four CSF measures, indicating no differential spatial frequency processing in ASD.Although it has been suggested that detail-oriented visual perception in individuals with ASD may be a result of differential sensitivities to low vs. high spatial frequencies, the current study finds no evidence to support this hypothesis.

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Section: Discussionmentioning

confidence: 99%

Spatial Contrast Sensitivity in Adolescents with Autism Spectrum Disorders

Koh

Milne

Dobkins

2010

J Autism Dev Disord

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“…Further supporting the collapsing of data for the UnCued-Single and Cued-Single conditions, an analysis of slopes of the psychometric functions also revealed no significant difference between mean slopes for the two (data from Subject Group 1-motion task: p = 0.99, 2-tailed t-test; orientation task: p = 0.33, 2-tailed t-test). Also, because sensitivity data are known to conform to normal distributions when log-transformed (Gunther and Dobkins, 2002), all statistical analyses and averages were performed on log threshold values. Pairwise comparisons (t-tests) were made between different conditions, selected a priori based on the reasoning explained in the Rationale segment of the Methods section above.…”

Section: Discussionmentioning

confidence: 99%

Attentional weighting: A possible account of visual field asymmetries in visual search?

Rezec

Dobkins

2004

Spatial Vis

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Several previous visual search studies measuring reaction times have demonstrated scanning biases across the visual field (i.e. a tendency to begin a serial search in a particular region of space). In the present study, we measured visual discrimination thresholds for a target presented amongst distractors using displays that were short enough to greatly reduce the potential for serial (i.e. scanning) search. For both a motion and orientation task, subjects' performance was significantly better when the target appeared in the inferior, as compared to the superior, visual field (no differences were observed between left and right visual fields). These findings suggest that subjects may divide attention unevenly across the visual field when searching for a target amongst distractors, a phenomenon we refer to as 'attentional weighting'. To rule out the possibility that these visual field asymmetries were sensory in nature, thresholds were also measured for conditions in which subjects' attention was directed to the location of the target stimulus, either because it was presented alone in the display or because a spatial cue directed subjects' attention to the location of that target presented amongst distractors. Under these conditions, visual field asymmetries were smaller (or non-existent), suggesting that sensory factors (such as crowding) are unlikely to account for our results. In addition, analyses of set-size effects (obtained by comparing thresholds for a single target vs. the target presented amongst distractors) could be accounted for by an unlimited capacity model, suggesting that multiple stimuli can be processed simultaneously without any limitations at an early stage of sensory processing. Taken together, these findings suggest the possible existence of biases in attentional weighting at a late stage of processing. The bias appears to favor the inferior visual field, which may arise from the fact that there is more ecologically-relevant information in this region of space.

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“…extreme L:M cone ratios have compromised color contrast sensitivity (Gunther and Dobkins, 2002) and have greater matching ranges on the anomaloscope than normal (Jordan and Mollon, 1993). As a result of the irregular assignment of L and M cones, these subjects would also tend to have larger patches of effectively color-blind retina (where only one cone class is present) than those with more balanced numbers of L and M cones.…”

Section: Interobserver Differences In L:m Cone Ratiomentioning

confidence: 99%

Organization of the Human Trichromatic Cone Mosaic

Hofer¹,

Carroll²,

Neitz³

et al. 2005

J. Neurosci.

389

311

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Using high-resolution adaptive-optics imaging combined with retinal densitometry, we characterized the arrangement of short-(S), middle-(M), and long-(L) wavelength-sensitive cones in eight human foveal mosaics. As suggested by previous studies, we found males with normal color vision that varied in the ratio of L to M cones (from 1.1:1 to 16.5:1). We also found a protan carrier with an even more extreme L:M ratio (0.37:1). All subjects had nearly identical S-cone densities, indicating independence of the developmental mechanism that governs the relative numerosity of L/M and S cones. L:M cone ratio estimates were correlated highly with those obtained in the same eyes using the flicker photometric electroretinogram (ERG), although the comparison indicates that the signal from each M cone makes a larger contribution to the ERG than each L cone. Although all subjects had highly disordered arrangements of L and M cones, three subjects showed evidence for departures from a strictly random rule for assigning the L and M cone photopigments. In two retinas, these departures corresponded to local clumping of cones of like type. In a third retina, the L:M cone ratio differed significantly at two retinal locations on opposite sides of the fovea. These results suggest that the assignment of L and M pigment, although highly irregular, is not a completely random process. Surprisingly, in the protan carrier, in which X-chromosome inactivation would favor L-or M-cone clumping, there was no evidence of clumping, perhaps as a result of cone migration during foveal development.

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Individual differences in chromatic (red/green) contrast sensitivity are constrained by the relative number of L- versus M-cones in the eye

Cited by 49 publications

References 66 publications

Spatial Contrast Sensitivity in Adolescents with Autism Spectrum Disorders

Spatial Contrast Sensitivity in Adolescents with Autism Spectrum Disorders

Attentional weighting: A possible account of visual field asymmetries in visual search?

Organization of the Human Trichromatic Cone Mosaic

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