The molecular genetics of color vision and color blindness.
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Biomedical subjects
Publications and source records attributed to T Piantanida.
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Increment thresholds for small test flashes measured on superimposed backgrounds sometimes differed depending on whether an observer was instructed to keep the background subjectively visible or (Troxler) faded. The magnitude and direction of the threshold change varied among observers. For some observers, the magnitude of the effect of such instructions also varied with background size, psychophysical method, and displacement of test from background. How the instructions and their presumed association with different phenomenological states affect thresholds is not known. However, these results show that the magnitude of effects and the shapes of psychophysically measured functions can be affected by the instructions followed by the observer, whether self-imposed or imposed by the experimenter.
The genetic polymorphism of human color vision is examined within the framework of a photopigment replacement model. An analysis of the X-linked recessive dichromacies and anomalous trichromacies indicates that one source of variability of normal color perception may be the inclusion of several distinct phenotypes in what is usually described as normal color vision. This analysis also reveals the cause of the dominance hierarchy at the protan and deutan loci, the perceptual effects of dosage compensation, and the phenotypes of various compound hemizygotes.