Document Detail

Color vision sensitivity in normally dichromatic species and humans.
MedLine Citation:
PMID:  15688546     Owner:  NLM     Status:  MEDLINE    
Spectral-sensitivity functions for large, long-duration increments presented on a photopic white background indicate that wavelength-opponent mechanisms mediate detection in both normal and dichromatic humans. Normal humans exhibit high color-vision sensitivity as they discriminate the color of spectral flashes at detection-threshold intensities. However, dichromatic humans require stimuli up to about 0.4 log units above detection intensity to see certain colors. This low color-vision sensitivity in human dichromats may be an abnormal condition involving a defect in postreceptoral color processing. To test this hypothesis, we determined color-discrimination thresholds in normally dichromatic species: chipmunk, 13-lined ground squirrel, and tree shrew. For comparison, we also tested humans with normal and abnormal (deutan) color vision with the same apparatus and methods. Animals were trained to perform spatial two-choice discrimination tasks for food reward. Detection thresholds were determined for increments of white, 460 nm, 540 nm, 560 nm, 580 nm, 500 nm/long-pass, and 500 nm/short-pass on white backgrounds of 1.25 cd/m2, 46 cd/m2, and 130 cd/m2. Animals were also trained to respond to the colored increments when paired with the white increment when both were at equally detectable intensities. Color-discrimination thresholds were determined by dimming stimulus pairs (colored vs. white) until the subjects could no longer make the discriminations. Results indicated that the normally dichromatic species could discriminate colored stimuli from white at a mean intensity of 0.1 (+/-0.1) log units above detection threshold. 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. In keeping with previous studies, normal human trichromats discriminated color near detection-threshold intensities but humans with deutan color vision required suprathreshold intensities to discriminate the color of middle and long wavelengths. This high color-vision sensitivity of normally dichromatic species suggest that the low color-vision sensitivity in dichromatic humans is an abnormal condition and indicates a possible defect in their postreceptoral color-vision processing.
Richard E van Arsdel; Michael S Loop
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Visual neuroscience     Volume:  21     ISSN:  0952-5238     ISO Abbreviation:  Vis. Neurosci.     Publication Date:    2004 Sep-Oct
Date Detail:
Created Date:  2005-02-02     Completed Date:  2005-03-01     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  8809466     Medline TA:  Vis Neurosci     Country:  England    
Other Details:
Languages:  eng     Pagination:  685-92     Citation Subset:  IM    
Air Force Research Laboratory, AFRL/HECV, Wright-Patterson Air Force Base, Ohio 45433, USA.
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MeSH Terms
Color Perception / physiology*
Color Perception Tests
Color Vision Defects / physiopathology*
Photic Stimulation
Retinal Cone Photoreceptor Cells / physiology
Sciuridae / physiology*
Sensory Thresholds / physiology*
Tupaia / physiology*
Grant Support
EY 07084-17/EY/NEI NIH HHS

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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