Harry G. Sperling

Differential spectral photic damage to primate cones

Abstract Selective loss of sensitivity to blue and green parts of the spectrum following intermittent, repeated exposures to intense spectral lights persists longer than 3 yr following blue lights and between 18 and 40 days following green lights. The “blue-blindness” involves complete and sole loss of the response of the short-wavelength responsive cones. The “green-blindness” involves complete and sole loss of response of middle-wavelength sensitive cones. Histo-pathology of cones in a “blue-blinded” retina in comparison with cytochemical labeling of short-wavelength cones, reveals that they follow a similar distribution: are sparse in the foveola. reach a peak of about 16% of the cones near 1 and fall to 8–12% of the cones at 7. Continuous as distinct from intermittent exposures to similar blue lights produces a wholly different picture of gross pigment-epithelial damage with little photoreceptor degeneration.

The chromatic organization of the goldfish cone mosaic

Abstract Responses of individual goldfish cones to spectral lights were monitored using reduction of Nitro-blue tetrazolium chloride as an indicator of response magnitude. Red sensitive cones (long double, some long single and miniature long single cones), green sensitive cones (short double and some long single cones) and blue sensitive cones (short single and miniature short single cones) were identified in flat mounts of whole retinae. Cone patterning, densities and dimensions were examined in whole mounts and thin sections. The total chromatic composition of the retina was found to be 45% red cones, 35% green cones and 20% blue cones.

Adaptive evolution of color vision genes in higher primates

The intron 4 sequences of the three polymorphic alleles at the X-linked color photo-pigment locus in the squirrel monkey and the marmoset reveal that the alleles in each species are exceptionally divergent. The data further suggest either that each triallelic system has arisen independently in these two New World monkey lineages, or that in each species at least seven deletions and insertions (14 in the two species) in intron 4 have been transferred and homogenized among the alleles by gene conversion or recombination. In either case, the alleles in each species apparently have persisted more than 5 million years and probably have been maintained by overdominant selection.

Prolonged Color Blindness Induced by Intense Spectral Lights in Rhesus Monkeys

Prolonged exposure of rhesus monkeys to intense blue light produces long-term changes which are consistent with loss of response of those cones that contain a photopigment with peak absorption at 445 nanometers. The 90 percent reduction of spectral sensitivity in the blue region has lasted more than 5 months. Reduced sensitivity to long wavelengths is produced by adaptation to light of 520 nanometers. This reduced sensitivity, which lasts no more than 30 days, is attributed to a temporary loss of response of the cones containing a photopigment with peak absorption at 535 nanometers.

Effects of intense visible radiation on the increment-threshold spectral sensitivity of the rhesus monkey eye.

Abstract The increment-threshold spectral sensitivity of adolescent rhesus monkeys was measured against intense spectral backgrounds, designed to isolate the response of each class of cones. The results are in good agreement with those produced by physical measurement techniques. Then functions were obtained against a 3400-td background of equal energy white before and after exposure for 1–2 hr/day for 6–10 consecutive days to spectral fields designed to maximally stimulate one of the receptor mechanisms. Two types of prolonged changes in sensitivity resulted: (1) an irreversible loss of sensitivity in only the violet and blue regions following exposure to narrow-band 463-nm light; (2) a change in sensitivity to the green through red region of the spectrum following exposure to longer wavelength light which in different animals began to recover after 1–6 days and was fully recovered by the 18th to 40th day. The effect of blue light exposure was fully accounted for by loss of response of the blue-sensitive, and of longer wavelength exposure by loss of response of the green-sensitive chromatic mechanism, because in each case the resultant functions could be modeled by omitting the one or the other.

Molecular Genetics of Spectral Tuning in New World Monkey Color Vision

Abstract. Although most New World monkeys have only one X-linked photopigment locus, many species have three polymorphic alleles at the locus. The three alleles in the squirrel monkey and capuchin have spectral peaks near 562, 550, and 535 nm, respectively, and the three alleles in the marmoset and tamarin have spectral peaks near 562, 556, and 543 nm, respectively. To determine the amino acids responsible for the spectral sensitivity differences among these pigment variants, we sequenced all exons of the three alleles in each of these four species. From the deduced amino acid sequences and the spectral peak information and from previous studies of the spectral tuning of X-linked pigments in humans and New World monkeys, we estimated that the Ala → Ser, Ile → Phe, Gly → Ser, Phe → Tyr, and Ala → Tyr substitutions at residue positions 180, 229, 233, 277, and 285, respectively, cause spectral shifts of about 5, −2, −1, 8, and 15 nm. On the other hand, the substitutions His → Tyr, Met → Val or Leu, and Ala → Tyr at positions 116, 275, and 276, respectively, have no discernible spectral tuning effect, though residues 275 and 276 are inside the transmembrane domains. Many substitutions between Val and Ile or between Val and Ala have occurred in the transmembrane domains among the New World monkey pigment variants but apparently have no effect on spectral tuning. Our study suggests that, in addition to amino acid changes involving a hydroxyl group, large changes in residue size can also cause a spectral shift in a visual pigment.

Isolation of a third chromatic mechanism in the deuteranomalous observer

Abstract The increment threshold spectral sensitivity of normal and deuteranomalous trichromats was measured. Under achromatic adaptation the normal trichromats showed evidence of three receptor mechanisms, the deuteranomalous trichromats only two. The thresholds of deuteranomalous observers who had been adapted to a combination of violet and red light showed these subjects to have a receptor system whose sensitivity curve was similar to chlorolabe, but with a sensitivity peak at 560 nm.

Red/green opponency in the rhesus macaque ERG spectral sensitivity is reduced by bicuculline

Spectral-sensitivity curves were derived from the a-, b-, and d-waves of rhesus monkey ERGs after injection of bicuculline, strychnine, or no drug. Without drug injection, the a- and d-wave curves were well-fit by an additive model of weighted photoreceptor absorption spectra, while the b-wave curve requires inhibitory terms to produce an adequate fit. Bicuculline, but not strychnine, reduced the weight assigned to the inhibitory terms in a dose-dependent fashion, to the point that no inhibition was evident. The results suggest that GABAergic synapses are required for the expression of red/green color opponency in primate bipolar cells.

Spectral sensitivity, intense spectral light studies and the color receptor mosaic of primates

Twenty five years ago when this journal was founded, except for the insights of a few radicals who favored zone theories (Mueller, 1930; Adams, 1942; Judd, 1951) color vision theorists were arguing about the same things as they had been in the nineteenth century. There was heated controversy between two camps based on different points of view and different psychophysical evidence. The one argued for the Young-Helmholtz theory of three independent receptor mechanisms which added their sensitivities to produced luminosity and color mixture data. The other included proponents of the Hering theory, which claimed that each photoreceptor mechanism was capable of a subtractive or opponent cancellation between pairs of primary colors and between black and white to give luminosity. Their evidence was largely from studies of color appearance, simultaneous color contrast, after-images studies and cancellation of primaries to match white. Both theories were one-stage theories in the form in which they were first proposed. Just before the founding of Vision Research, Svaetichin (1956) had taken the first big step which eventually led to the unraveling of the two theories. He recorded intracellularly from the outer plexiform layer of the fish retina and found that single neural units, which turned out to be horizontal cells (see Tomita and MacNichol, this issue), hyperpolarized to one part of the spectrum and depolarized to another. This must be a second stage combination of signals from two classes of photoreceptors, thus supporting the multi-stage theories of color vision (Mueller, Adams, Judd op. cit.).

Color vision following intense green light exposure: Data and a model

Hue discrimination, spectral sensitivity, and mathematical models of both are presented for a rhesus monkey which was exposed to intense green light. One of the monkeys eyes was blue-blinded in a previous experimental procedure and the other was color normal. The results of green light exposure showed a loss of sensitivity on both measures, with greater loss in the blue-blinded eye. Although there was considerable loss of hue-discrimination in the blue-green spectral regions, hue-discrimination at the point of best discrimination, 590 nm, remained unaffected. This pattern of results poses difficulties for models of hue discrimination, and has resulted in the proposed model employing three opponent color channels. The number of free-parameters are minimized and the integration between spectral sensitivity and hue discrimination enhanced by deriving parameters used in modeling hue discrimination from spectral sensitivity or vice versa.