Evidence for transient luminance and quasi-sustained color mechanisms

Schwartz, Steven H.; Loop, Michael S.

doi:10.1016/0042-6989(82)90192-4

Cited by 30 publications

(22 citation statements)

References 14 publications

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“…The results obtained with this procedure are consistent with those of Tolhurst (1977) and Schwartz and Loop (1982), who suggested that the output of the chromatic system is sustained relative to that of the achromatic system. Schwartz and Loop determined reaction time (RT) distributions to longduration near-threshold increments.…”

Section: Results and Conclusionsupporting

confidence: 80%

“…Experimental evidence supporting this hypothesis has been presented by Tolhurst (1977), who demonstrated that a long-duration subthreshold pulse enhances sensitivity of the chromatic system for a longer period of time than it does for the achromatic system. Reaction time distributions (Schwartz & Loop, 1982) obtained in response to long-duration near-threshold increments are also consisistent with this suggestion. In this paper, detectability is determined as a function of stimulus duration for both the chromatic and achromatic systems.…”

supporting

confidence: 57%

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Effect of duration on detection by the chromatic and achromatic systems

Schwartz

Loop

1984

Perception & Psychophysics

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and MICHAEL S. LOOP University ofAlabama, Birmingham, AlabamaDetectability was determined as a function of stimulus duration for the chromatic and achromatic systems. For the achromatic system, detectability remains relatively constant for durations ranging from 43 to 1,000 msec, whereas for the chromatic system, detectability increases with duration up to about 500 msec. This suggests that the chromatic system has a more sustained output than the achromatic system.

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Section: Results and Conclusionsupporting

confidence: 80%

supporting

confidence: 57%

Effect of duration on detection by the chromatic and achromatic systems

Schwartz

Loop

1984

Perception & Psychophysics

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“…For example, low spatial frequencies are processed faster than high spatial frequencies (Breitmeyer & Ganz, 1976;Green, 1984), and they form faster than color (e.g., Schwartz & Loop, 1982). If the display is presented during an eye movement, the different processing times may cause features to be coded at different retinotopic locations.…”

Section: Evaluation Of Blackboard and Network Architecturesmentioning

confidence: 99%

Visual search, visual streams, and visual architectures

Green

1991

Perception & Psychophysics

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Most psychological, physiological, and computational models of early vision suggest that retinal information is divided into a parallel set of feature modules. The dominant theories of visual search assume that these modules form a "blackboard" architecture: a set of independent representations that communicate only through a central processor. A review of research shows that blackboard-based theories, such as feature-integration theory, cannot easily explain the existing data. The experimental evidence is more consistent with a "network" architecture, which stresses that: (1) feature modules are directly connected to one another, (2) features and their locations are represented together, (3) feature detection and integration are not distinct processing stages, and (4) no executive control process, such as focal attention, is needed to integrate features. Attention is not a spotlight that synthesizes objects from raw features. Instead, it is better to conceptualize attention as an aperture which masks irrelevant visual information.Two factors make early vision a difficult computational problem. First, the solution space is combinatorially explosive because images contain a large number of feature dimensions. Second, computation must be rapid, so processing time is limited. Many theories suggest that the visual system solves these problems by means of a divideand-eonquer strategy; the retinal image is decomposed into an array of separate representations that are processed in parallel.

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“…These reaction time findings suggest that both color-normal and color-abnormal humans detect spectral increments with a sustained response mechanism thought to be typical of color-opponent neural mechanisms (Schwartz, 1992;Schwartz & Loop, 1982).…”

Section: Subjectsmentioning

confidence: 92%

“…Further, several characteristics of normal human detection of spectral increments indicate mediation by opponent neural pathways. For example, psychophysical measurements of human dichromats to colored stimuli indicate long temporal integration (King-Smith & Carden, 1976), slow and sustained threshold reaction times (Schwartz & Loop, 1982), and a sluggish temporal appearance (Schwartz & Loop, 1983).…”

Section: Subjectsmentioning

confidence: 99%

Color vision sensitivity in normally dichromatic species and humans

Arsdel

Loop

2004

Vis Neurosci

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Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188), Washington, DC 20503. AGENCY USE ONLY (Leave blank)2. REPORT DATE 23.Sep.02 REPORT TYPE AND DATES COVERED DISSERTATION TITLE AND SUBTITLE COLOR VISION SENSITIVITY IN NORMALLY DICHROMATIC SPECIES AND HUMANS AUTHOR(S)LT COL VAN ARSDEL RICHARD E FUNDING NUMBERS PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)UNIVERSITY OF ALABAMA AT BIRMINGHAM Spectral sensitivity functions for large, long-duration spectral stimuli presented on a photopic white background indicate that wavelength opponent mechanisms mediate detection of such stimuli in both normal and dichromatic humans. Normal humans detect the color of spectral flashes at detection threshold intensities, supporting the premise that wavelength opponent processes signal color. However, dichromatic humans do not see some colors at threshold; rather, they require stimuli up to about 0.4 log units above detection intensity. This suggests that dichromatic humans may have a defect in postreceptoral color processing. To test this, we determined color discrimination thresholds in normally occurring dichromats, including the chipmunk, the 13-lined ground squirrel, and the tree shrew.Animals were trained with food to perform spatial two-choice discrimination tasks. Detection thresholds were first determined for white, 460-nm, 540-nm, 560-nm, 580-nm, 500-nm long-pass, and 500-nm short-pass increments on white backgrounds of 1.25 cd/m 2 ,46 cd/m 2 , and 130 cd/m 2 . Animals were then trained to respond to the colored increments when paired with the white when both were at an intensity of 0.5 log units above each animal's detection threshold. Color discrimination thresholds were then determined by dimming stimulus pairs (colored vs. white) until the subjects could no longer make the discriminations.u Data indicate that the normally dichromatic species discriminated the color from the white stimuli at a mean intensity of 0.1 (±0.1) log units above detection threshold in photopic conditions. The ability of normally dichromatic species to discriminate color near detection threshold intensity is consistent with increment spectral sensitivity functions that indicate detection by wavelength opponent mechanisms. This high color sensitivity of normal dichromats suggests that the low color vision sensitivity of dichromatic humans is an abnormal condition and indicates a possible defect in postreceptoral processing, but the...

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Evidence for transient luminance and quasi-sustained color mechanisms

Cited by 30 publications

References 14 publications

Effect of duration on detection by the chromatic and achromatic systems

Effect of duration on detection by the chromatic and achromatic systems

Visual search, visual streams, and visual architectures

Color vision sensitivity in normally dichromatic species and humans

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