Color vision sensitivity in normally dichromatic species and humans

Abstract

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...

Advantages and disadvantages of human dichromacy

“…Certain aspects of these issues have been investigated before (Loop et al, 2003;Schwartz, 1994;van Arsdel & Loop, 2004). Intriguingly, dichromatic humans require long-duration spectral increments to be as much as 0.4 log unit above detection intensity to see certain colors, whereas normally dichromatic animals such as chipmunks, 13-lined ground squirrels, and tree shrews are able to discriminate colors within 0.1 log unit of their detection thresholds (Loop et al, 2003;van Arsdel & Loop, 2004). This low color vision sensitivity in human dichromats may be an abnormal condition, indicating a possible defect in their postreceptoral color vision processing.…”

“…Previously, other researchers have investigated the disadvantages of dichromats in visual detection (e.g., Dain & King-Smith, 1981;Loop, Shows, Mangel, & Kuyk, 2003;Schwartz, 1994;van Arsdel & Loop, 2004). However, they have not used cone-isolating stimuli to examine the influence of both slow and fast temporally modulated stimuli in the same group of observers or species.…”

The Representation of S-Cone Signals in Primary Visual Cortex

“…In this study, we sought insights into the fundamental features of cortical organization necessary for S-cone mediated color vision by examining the cortical processing of S-cone inputs in the tree shrew, a highly visual dichromatic mammal with a cone-dominated retina, strong color vision capabilities, and a well-characterized V1 functional architecture (Jacobs and Neitz, 1986; Petry and Harosi, 1990; Petry and Kelly, 1991; Muly and Fitzpatrick, 1992; Fitzpatrick, 1996; Bosking et al, 1997; Bosking et al, 2002; van Arsdel and Loop, 2004). Our results indicate that S-cones contribute to both chromatic and achromatic visual functions and suggest that the conjoint representation of color and form is a fundamental property of cortical processing.…”

A torsional eye movement calculation algorithm for low contrast images in video-oculography

“…On the same recordings, the template-matching method of [9] Fig. 10. Histogram of the differences in degrees between the search coil technique and our algorithm.…”

“…All studies rely heavily on the texture of the iris, which is clearly visible and directly applicable when daylight or light of particular wavelengths is used. However, in the clinical applications of our setting, to avoid visual fixation, a wavelength to illuminate the eye is required, which cannot be perceived by the human retina, [10]. Therefore, 950 nm IR-LEDs are used, as LEDs centered at lower wavelengths still emit light that after adaptation can be seen by the human eye.…”