Human trichromacy revisited

The presence of a photopigment (melanopsin) within certain retinal ganglion cells was a surprising and significant discovery. This pigment is routinely described as “nonvisual” to highlight its signaling role in pupil dilation and circadian rhythms. Here we asked whether light absorbed by melanopsin...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2013-01, Vol.110 (3), p.E260-E269
Main Authors: Horiguchi, Hiroshi, Winawer, Jonathan, Dougherty, Robert F, Wandell, Brian A
Format: Article
Language:English
Subjects:
Adult
Biological Sciences
Color Vision - physiology
Female
Fovea Centralis - physiology
Human subjects
Humans
Light
Male
Models, Biological
Optical Phenomena
Photic Stimulation
Photochemistry
Pigments
PNAS Plus
Retina
Retina - physiology
Retinal Cone Photoreceptor Cells - physiology
Retinal Pigments - physiology
Retinal Rod Photoreceptor Cells - physiology
Rod Opsins - physiology
Signal transduction
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Summary:The presence of a photopigment (melanopsin) within certain retinal ganglion cells was a surprising and significant discovery. This pigment is routinely described as “nonvisual” to highlight its signaling role in pupil dilation and circadian rhythms. Here we asked whether light absorbed by melanopsin can be seen by healthy human subjects. To answer this requires delivering intense (above rod saturation), well-controlled lights using four independent primaries. We collected detection thresholds to many four-primary stimuli. Threshold measurements in the fovea are explained by trichromatic theory, with no need to invoke a fourth photopigment. In the periphery, where melanopsin is present, threshold measurements deviate from trichromatic theory; at high photopic levels, sensitivity is explained by absorptions in four, not three, photopigment classes. We consider a series of hypotheses to explain the tetrasensitivity at high photopic levels in the human peripheral field. The most likely hypothesis is that in healthy human subjects melanopsin absorptions influence visibility.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1214240110