SUMMARY1. Atypical (blue cone) monochromats show two action spectra when tested by the increment threshold method of Stiles with' central' fixation. One spectrum peaks near 450 nm and has the spectral characteristics of normal blue cones. The other resembles rhodopsin (r0) modified slightly by photostable macular pigment.2. Under some circumstances such observers are dichromats. There is a neutral point (matched to Illuminant 'C') in the neighbourhood of 460-470 nm.3. The spectral colour matching functions using two primaries have been measured on three such subjects. They can be fit reasonably well, although imperfectly, by linear combinations of oro and nr1. The chromaticity co-ordinates have been calculated according to the convention of W. D. Wright and compared to the results predicted from no and or1. The comparison suggests that part of the imperfections of the colour matching function fit is due to prereceptor differences (e.g. macular pigment) between the blue-cone monochromats and the hypothetical sTOp, iT observer.4. Colour matches made at high light levels continue to hold when the intensity of the field is reduced below the cone threshold.5. Therefore one of the visual pigments participating in the colour matches has an action spectrum which is not measurably different from that of the rod pigment rhodopsin.6. Increment threshold measurements show that the mechanism which has the rhodopsin action spectrum has the directional sensitivity of cones, not rods.7. Blue test threshold during dark adaptation after a full bleach follow a bipartite exponential recovery curve. The first exponential has a time constant of 1 min, the second 2 min. By comparing these curves to the increment thresholds it is possible to relate the first to the oTr, the second to the 7T0 cones.8. Using a broad band blue gelatin filter in the measuring light of the M. ALPERN AND OTHERS retinal densitometer and studying the same retinal region tested in 7 it is possible to follow the regeneration of a pigment after a full bleach which has an exponential recovery with a time constant of 10 min. With a yellow green filter in the measuring light the exponential recovery observed after a full bleach has a time constant of 2-0 min. 9. One of the two visual pigments participating in the colour matches resides in receptors which have the action spectrum, the directional sensitivity and probably the dark adaptation curve of normal blue cones.10. The other resides in receptors which have the action spectrum of normal rods but the directional sensitivity and the dark adaptation curve of normal red and green cones.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.