Human trichromacy revisited

Hiroshi Horiguchi, Jonathan Winawer, Robert F. Dougherty, Brian A. Wandell

Research output: Contribution to journalArticlepeer-review


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.

Original languageEnglish (US)
Pages (from-to)E260-E269
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number3
StatePublished - Jan 15 2013


  • Color perception
  • Flicker sensitivity
  • Retina
  • ipRGC

ASJC Scopus subject areas

  • General


Dive into the research topics of 'Human trichromacy revisited'. Together they form a unique fingerprint.

Cite this