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Journal of the Optical Society of America

Journal of the Optical Society of America

  • Vol. 71, Iss. 9 — Sep. 1, 1981
  • pp: 1134–1137

Stiles’s π5 mechanism: failure to show univariance is caused by opponent-channel input

Carl R. Ingling, Jr. and Eugenio Martinez  »View Author Affiliations

JOSA, Vol. 71, Issue 9, pp. 1134-1137 (1981)

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Stiles’s π5 field sensitivity approaches the sensitivity of the long-wavelength (L) cone as the duration of the test flash decreases. Further, for short test flashes mixtures of red and green backgrounds are additive. For long test flashes the backgrounds cancel, the mixture raising threshold less than expected. These results are explained if π5 is approximately the L-cone sensitivity combined with some opponent-channel sensitivity.

© 1981 Optical Society of America

Carl R. Ingling, Jr. and Eugenio Martinez, "Stiles’s π5 mechanism: failure to show univariance is caused by opponent-channel input," J. Opt. Soc. Am. 71, 1134-1137 (1981)

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  1. J. M. Enoch, "The two-color threshold technique of Stiles and derived component color mechanisms," in Handbook of Sensory Physiology, Volume VII/4, D. Jameson and L. M. Hurvich, eds. (Springer-Verlag, New York, 1972), pp. 537–567; G. Wyszecki and W. S. Stiles, Color Science (Wiley, New York, 1967), pp. 571–580; W. S. Stiles, Mechanisms of Colour Vision (Academic, New York, 1978).
  2. C. R. Ingling, Jr., and B. H. -P. Tsou, "Orthogonal combination of the three visual channels," Vision Res. 17, 1075–1082 (1977).
  3. E. N. Pugh, Jr., and C. Sigel, "Evaluation of the candidacy of the mechanisms of Stiles for color-matching fundamentals," Vision Res. 18, 317–330 (1978); J. K. Bowmaker, H. J. A. Dartnall, J. N. Lythgoe, and J. D. Mollon, "The visual pigments of rods and cones in the rhesus monkey, Macaca mulatta," J. Physiol. London 274, 329–348 (1978); C. Sigel and E. N. Pugh, Jr., "Stiles's π5 color mechanism: tests of field displacement and field additivity properties," J. Opt. Soc. Am. 70, 71–81 (1980).
  4. S. L. Guth and H. R. Lodge, "Heterochromatic additivity, foveal spectral sensitivity, and a new color model," J. Opt. Soc. Am. 63, 450–462 (1973); S. L. Guth, R. W. Massof, and T. Benzschawel, "Vector model for normal and dichromatic color vision," J. Opt. Soc. Am. 70, 197–212 (1980).
  5. "Light as a true visual quality: principles of measurements," CIE Technical Report of Tech. Comm. TC 1.4 (National Bureau of Standards, Washington, D.C., 1978).
  6. The L-cone sensitivity is from Smith and Pokorny, Eye Research Laboratories, University of Chicago, Chicago, Illinois, personal communication, and is tabulated in Ref. 2 above. This comparison does not depend on choosing a particular L-cone fundamental sensitivity; e.g., Vos and Walraven's (Ref. 10) R cone could be used.
  7. For a review of the temporal physiological properties of chromatic and achromatic channels, see C. R. Ingling, Jr., "Luminance and opponent color contributions to visual detection and to temporal and spatial integration: comment," J. Opt. Soc. Am. 68, 1143– 1146 (1978).
  8. See Pugh and Sigel, Ref. 3, who come to the same conclusion; for threshold elevations below 1.0 log unit, the backgrounds obey the displacement rule.
  9. R. M. Boynton and S. R. Das, "Visual adaptation: increased efficiency resulting from spectrally distributed mixtures of stimuli," Science 154, 1581–1583 (1966); R. M. Boynton, S. R. Das, and J. Gardiner, "Interactions between photopic visual mechanisms revealed by mixing conditioning fields," J. Opt. Soc. Am. 56, 1775–1780 (1966). These authors tested the additivity of backgrounds and found supersummation instead of cancellation. This may have occurred because their test-flash wavelengths were too short and did not isolate π5 for all adaptations. If so, when the backgrounds are mixed, any nonlinear (compressive) adaptation produces supersummation. Pugh and Sigel in Ref. 3 above discuss other possibilities.
  10. J. J. Vos and P. L. Walraven, "On the derivation of the foveal receptor primaries," Vision Res. 11, 799–818 (1970).
  11. J. K. Bowmaker and H. J. A. Dartnall, "Visual pigments of rods and cones in a human retina," J. Physiol. 298, 501–511 (1980); J. K. Bowmaker, H. J. A. Dartnall, and J. D. Mollon, "Microspectrophotometric demonstration of four classes of photoreceptor in an Old World primate, Macaca fasicularis," J. Physiol. 298, 131–143 (1980).
  12. B. A. Wandell and E. N. Pugh, Jr., "A field additive pathway detects brief-duration, long-wavelength incremental flashes," Vision Res. 20, 613–624 (1980); "Detection of long-duration, long-wavelength incremental flashes by a chromatically coded pathway," Vision Res. 20, 625–636 (1980).

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