Organization of the Human Trichromatic Cone Mosaic

• Published in: The Journal of neuroscience Vol. 25; no. 42; pp. 9669 - 9679
• Main Authors: Hofer, Heidi, Carroll, Joseph, Neitz, Jay, Neitz, Maureen, Williams, David R
• Format: Journal Article
• Language: English
• Published: United States Soc Neuroscience 19.10.2005; Society for Neuroscience
• Subjects: Behavioral/Systems/Cognitive; Color Perception - physiology; Color Vision Defects - genetics; Color Vision Defects - pathology; Electroretinography - methods; Female; Humans; Male; Retinal Cone Photoreceptor Cells - cytology; Retinal Cone Photoreceptor Cells - pathology; Retinal Cone Photoreceptor Cells - physiology
• ISSN: 0270-6474; 1529-2401; 1529-2401
• DOI: 10.1523/JNEUROSCI.2414-05.2005

Using high-resolution adaptive-optics imaging combined with retinal densitometry, we characterized the arrangement of short- (S), middle- (M), and long- (L) wavelength-sensitive cones in eight human foveal mosaics. As suggested by previous studies, we found males with normal color vision that varied in the ratio of L to M cones (from 1.1:1 to 16.5:1). We also found a protan carrier with an even more extreme L:M ratio (0.37:1). All subjects had nearly identical S-cone densities, indicating independence of the developmental mechanism that governs the relative numerosity of L/M and S cones. L:M cone ratio estimates were correlated highly with those obtained in the same eyes using the flicker photometric electroretinogram (ERG), although the comparison indicates that the signal from each M cone makes a larger contribution to the ERG than each L cone. Although all subjects had highly disordered arrangements of L and M cones, three subjects showed evidence for departures from a strictly random rule for assigning the L and M cone photopigments. In two retinas, these departures corresponded to local clumping of cones of like type. In a third retina, the L:M cone ratio differed significantly at two retinal locations on opposite sides of the fovea. These results suggest that the assignment of L and M pigment, although highly irregular, is not a completely random process. Surprisingly, in the protan carrier, in which X-chromosome inactivation would favor L- or M-cone clumping, there was no evidence of clumping, perhaps as a result of cone migration during foveal development.