Red-green Color Discrimination Research Articles

Information gains from commercial spectral filters in anomalous trichromacy.

Red-green color discrimination is compromised in anomalous trichromacy, the most common inherited color vision deficiency. This computational analysis tested whether three commercial optical filters with medium-to-long-wavelength stop bands increased information about colored surfaces. The surfaces were sampled from 50 hyperspectral images of outdoor scenes. At best, potential gains in the effective number of surfaces discriminable solely by color reached 9% in protanomaly and 15% in deuteranomaly, much less than with normal trichromacy. Gains were still less with lower scene illumination and more severe color vision deficiency. Stop-band filters may offer little improvement in objective real-world color discrimination.

IMPAIRMENTS OF L-CONE/M-CONE AND S-CONE-MEDIATED COLOR DISCRIMINATION IN MACULAR TELANGIECTASIA TYPE II.

To characterize red-green and tritan color discrimination in eyes with macular telangiectasia Type II (MacTel). Color discrimination was assessed by metameric matching methods using an Oculus MR Anomaloscope. Red-green color discrimination was assessed using the Rayleigh equation, and tritan color discrimination was assessed using the Moreland equation. Results were expressed as anomalquotient (AQ) and tritanomalquotient (TAQ) units, respectively. Seventeen eyes with MacTel were compared with 16 control eyes with normal vision. Twelve eyes with MacTel demonstrated abnormal color matches; except for two eyes with red-shifted Rayleigh matches, the primary abnormality evident was reduced color discrimination. On average, Rayleigh matching ranges were significantly widened in MacTel (0.518 ± 0.066 AQ units) compared with normal (0.14 ± 0.03 AQ units; P < 0.0001). Similarly, Moreland matching ranges were significantly wider (0.794 ± 0.109 TAQ units) than normal control subjects (0.204 ± 0.070 TAQ units; P < 0.0001). Losses in color discrimination did not correlate significantly with the best-corrected visual acuity, although Moreland matching ranges were significantly correlated to Rayleigh matching ranges. MacTel results in a combined acquired red-green and tritan color vision deficiency. A minority of eyes demonstrated red-shifted Rayleigh matches, consistent with decreases in cone photopigment optical density.

Transfer of incompatible spatial mapping to the vertical Simon task generalizes across effectors but not stimulus features.

For the vertical Simon task, in which stimuli and responses are arrayed along the vertical dimension and stimulus location is irrelevant, a Simon effect (benefit for stimulus-response correspondence) is typically obtained. Results have been mixed about whether performing fewer than 100 trials of a spatially incompatible mapping prior to a Simon task reduces or eliminates this vertical Simon effect in a transfer session. Several reasons have been suggested to explain why previous studies show disparate results. Previously, we ruled out orientation of the response panel in the transverse or horizontal plane as a critical factor. The present experiments evaluated two other possible factors: finger/hand placement and relevant stimulus dimension. In Experiment 1, we found reduction of the vertical Simon effect for a circle-square discrimination after incompatible practice using a separate numeric keypad as the response device, regardless of whether the keypad was placed on a table and operated by index fingers or held in the hands and operated by thumbs. In Experiment 2, we replicated the reduction for the circle-square discrimination but found no evidence of reduction for a red-green color discrimination. Overall, our results suggest that the relevant discrimination of red-green color versus circle-square shape is responsible for the discrepancy in results across prior studies.

Monkeys Quickly Learn and Generalize Visual Categories without Lateral Prefrontal Cortex

Categorization is a basic mental process that helps individuals distinguish among groups of negative and positive objects, e.g., poisons and nutrients, or predators and prey. Monkey experiments have suggested that lateral prefrontal cortex (LPFC) participates in learning and processing visual categories. However, in humans category specific visual agnosia follows inferior temporal cortex but not LPFC damage. Here, we use a new behavioral approach to show that both normal monkeys and those with bilateral removal of LPFC learn and generalize perceptual categories of related visual stimuli rapidly without explicit instruction. These results strongly indicate that visual categorization occurs at some earlier stage of feed-forward processing, presumably in temporal cortex, without top-down information from LPFC.

Measuring and modeling the interaction among reward size, delay to reward, and satiation level on motivation in monkeys.

Motivation is usually inferred from the likelihood or the intensity with which behavior is carried out. It is sensitive to external factors (e.g., the identity, amount, and timing of a rewarding outcome) and internal factors (e.g., hunger or thirst). We trained macaque monkeys to perform a nonchoice instrumental task (a sequential red-green color discrimination) while manipulating two external factors: reward size and delay-to-reward. We also inferred the state of one internal factor, level of satiation, by monitoring the accumulated reward. A visual cue indicated the forthcoming reward size and delay-to-reward in each trial. The fraction of trials completed correctly by the monkeys increased linearly with reward size and was hyperbolically discounted by delay-to-reward duration, relations that are similar to those found in free operant and choice tasks. The fraction of correct trials also decreased progressively as a function of the satiation level. Similar (albeit noiser) relations were obtained for reaction times. The combined effect of reward size, delay-to-reward, and satiation level on the proportion of correct trials is well described as a multiplication of the effects of the single factors when each factor is examined alone. These results provide a quantitative account of the interaction of external and internal factors on instrumental behavior, and allow us to extend the concept of subjective value of a rewarding outcome, usually confined to external factors, to account also for slow changes in the internal drive of the subject.

Lesions in the basal ganglion and hippocampus on performance in a Wisconsin Card Sorting Test-like task in pigeons

Previous studies of LPO (lobus parolfactorium) and hippocampal lesions in pigeons suggest function of cognitive flexibility in LPO and memory consolidation in hippocampus [Watanabe S. Effects of hippocampal lesions on repeated acquisition of spatial discrimination in pigeons. Behav Brain Res 2001;120:59–66. [40]; Watanabe S. Effects of LPO lesions on repeated acquisition of spatial discrimination in pigeons. Brain Behav Evol 2002;58:333–342. [41]]. Here, a test similar to the Wisconsin Card Sorting Test was applied to pigeons. The test consisted of four discriminations, namely red–green color discrimination and its reversal, left–right spatial discrimination and its reversal. In each trial stimuli were presented until the correct choice occurred. Ten successive correct trials without wrong response were defined as the criterion of discrimination. When the subjects reached the criterion in one discrimination, they were trained on one of three other discrimination tasks in the next session. These four discriminations were trained repeatedly in random sequence. After the birds have been well learned the WCST-like task, their hippocampus or lobus parolfactorium (LPO), the avian basal ganglion, was damaged. A sham lesion group received anesthesia only. Both lesions impaired the WCST-like test. Lesions of the LPO increased the number of errors, while the hippocampal lesions increased the number of trials to reach the criterion only. The number of errors reflects difficulty in finding the correct stimulus or cognitive flexibility, while the number of trials reflects difficulty in stable responding or memory consolidation. The present results suggest that LPO has the function of cognitive flexibility.

The molecular basis of dichromatic color vision in males with multiple red and green visual pigment genes.

We investigated the genotypic variation in 50 red-green color vision deficient males (27 deuteranopes and 23 protanopes) of middle European ancestry who possess multiple genes in the X-linked photopigment gene array. We have previously shown that only the first two genes of the array are expressed and contribute to the color vision phenotype. Therefore, the hypothesis is that the first two genes possessed by multigene-dichromats encode pigments of identical or nearly identical spectral sensitivity: one gene normal (R or G) and the other a hybrid (G/R or R/G). The spectral sensitivities of the encoded pigments were inferred from published in vitro and in vivo data. The color vision phenotype was assessed by standard anomaloscopy. Most genotypes (92%) included hybrid genes whose sequence and position and whose encoded pigment correlated exactly with the phenotype. However, one and possibly two of the protanopes had gene arrays consistent with protanomaly rather than protanopia, since two spectrally different pigments may be encoded by their arrays. Two of the deuteranopes had only R- and G-photopigment genes, without any detectable G/R-hybrid genes or any as-of-yet identified point mutation or coding/promoter sequence deletions. Further, an unexpectedly high number of multigene-deuteranopes (11%) had the C203R mutation in their most upstream G-pigment gene, suggesting a founder effect of middle European origin for this mutation. About half of the protanopes possessed an upstream R/G-hybrid gene with different exon 2 coding sequences than their downstream G-pigment gene(s), which is inconsistent with published data implying that a single amino acid substitution in exon 2 can confer red-green color discrimination capacity on multigene-protans by altering the optical density of the cones.

Red–green color discrimination as a function of stimulus field size in peripheral vision

Red-green color-discrimination thresholds were measured at eccentricities of 10 and 25 deg in the nasal retina. Thresholds were measured as a function of stimulus field size both during the cone plateau and after dark adaptation. During the cone plateau, threshold decreased with increasing field size, but the effect of field size was dependent on the color of the test stimulus. The decrease in threshold was greater for yellow and orange test stimuli than for red and green tests. Two factors, summation and opponent-mechanism adaptation, appear to affect the relation between threshold and field size. An equation suggested by Boynton and Kambe in 1980 [Color Res. Appl. 5, 13 (1980)] provides a good description of the variation in thresholds with field size and eccentricity. After dark adaptation, thresholds increased for all test colors, suggesting that rod signals reduce discrimination. The dark-adapted thresholds could be described well by the addition of a rod term to the Boynton-Kambe equation.

Red-green color discrimination in peripheral vision

Color discrimination thresholds were measured for four colors from the red-green portion of the visible spectrum. Thresholds were measured for a stimulus field 1.5 deg in diameter in the fovea and at three locations on the nasal retina (eccentricities of 5, 20 and 40 deg). Outside the fovea thresholds increased exponentially with eccentricity and the slope of the function was similar for all four standard colors. Peripheral thresholds were adequately described by an equation developed for foveal red-green thresholds by Boynton and Kambe [(1980) Color Research and Applications, 5, 13–23] and also by a modified form of this equation containing a rod term. Differences between foveal and peripheral thresholds were characterized by changes in two coefficients in the equations. The CIELUV color difference equation also provided a reasonably good description of peripheral thresholds.

Red-green mixture thresholds in congenital and acquired color defects

A color television display was used to measure thresholds for mixtures of red and green on a white background; red and green components could be either incremental, decremental or zero. Ellipses are fitted to a plot of green contrast as a function of red contrast, and it is argued that the length of the ellipse is a measure of red-green color discrimination and the width of the ellipse is a measure of luminance discrimination. It is shown that the technique reliably distinguishes normals from congenital color defectives and also protan from deutan subjects. For some cases of acquired color defects (e.g. optic neuritis), there is a roughly equal loss of color and luminance discrimination whereas, in other cases (e.g. hereditary optic atrophies), the loss of color discrimination is much greater than the loss of luminance discrimination.

The Side Effects and Interactions of Antituberculosis Drugs

Antituberculosis drugs may produce side effects varying from unimportant to life-threatening. The side effects of drugs prescribed for a patient must be known, as well as whether it is necessary to monitor for such effects. Table 1 lists the side effects and recommendations for monitoring of antituberculosis drugs used in the United States; only the most commonly used drugs, the so-called first-line drugs, will be reviewed in the text. Table 1Drug Side Effects Drug Side Effects Monitoring Remarks Isoniasid Peripheral neuritis Pyridoxine: 10 mg for prophylaxis; 50 to 100 mg. for treatment Hepatitis SGOT, SGPT (if symptomatic) Discontinue if symptomatic + /or liver ensymes more than twice normal Central nervous system convulsions optic neuritis with atrophy muscle twitching dissiness ataxia toxic encephalopathy Hypersensitivity: fever, rash Drug interactions: Diphenylhydantoin somnolence Observe for overdose Ethambutol Optic neuritis Visual acuity and red-green color discrimination Unreported at 15 mg/kg dose; occurs at 25 mg/kg. Use with caution in presence of renal insufficiency Skin rash Rifampin Orange urine, tears, saliva Reassure patient Flu-like syndrome Need not discontinue rifampin and may restart if do discontinue Hepatitis SGOT, SGPT (if symptomatic) Discontinue if jaundice +/or liver enzymes more than twice normal Thrombocytopenia Platelet count (if suspected) Anti-rifampin antibodies absorbed on platelets, fix complement, results in platelet damage; discontinue rifampin Hemolysis Drug related antibody fixes and activates complement; discontinue Renal failure Probably on immunologic basis Drug Interactions: Warfarin Prothrombin time Rifampin decreases the hypoprothrombinemic effect of warfarin; warfarin dose may need to be reduced when rifampin discontinued Oral contraceptives Pregnancy reported in women on rifampin and oral contraceptives which may have accelerated catabolism caused by ensyme induction Methadone Rifampin may be associated with withdrawal symptoms in patients on a methadone maintenance program; also probably related to accelerated catabolism caused by ensyme induction PAS Concomittant administration of PAS and rifampin may lead to decreased absorption of rifampin In vitro immunosuppression Apparently not clinically significant Streptomycin 8th cranial nerve damage Audiogram Vestibular function Use with caution in presence of renal insufficiency Nephrotoxicity BUN, creatinine Neuromuscular junction blockade Seen in patients also receiving muscle relaxants Hypersensitivity reactions—rash, dermatitis, analyphylasis Pyrasinamide Hyperuricemia—acute gout Uric acid Hyperuricemia common; acute gout rare Hepatotoxicity SGOT, SGPT (if symptomatic) More common with high dosage Gastrointestinal—anorexia, nausea Diabetes mellitis more difficult to manage PAS Gastrointestinal—anorexia, nausea Gastrointestinal intolerance extremely common in adult, less so in children Hypersensitivity reactions—fever, rash, arthritis Discontinue Hepatotoxicity SGOT, SGPT (if symptomatic) Sodium load Ethionamide Gastrointestinal—anorexia, nausea, vomiting Divided dose may help control gastrointestinal side-effects Postural hypotension, depression, asthenia, drowsiness Skin rash, purpura, gynecomastia, impotence Hepatotoxicity SGOT, SGPT Cycloserine Central nervous system somnolence headache tremor dysarthria vertigo abnormal behavior psychosis seizures More common with higher dosage and in presence of ethanol; serum levels may help; anticonvulsants have been used to control seizures Hypersensitivity—rash Kanamycin 8th cranial nerve damage Audiogram vestibular function Nephrotoxicity BUN, creatinine Vestibular toxicity Hypersensitivity reactions—rash, pruritus Neuromuscular junction blockade Should be given with care to patients receiving muscle relaxants Capreomycin 8th cranial nerve damage Audiogram Use with caution in older patients and in presence of renal insufficiency Nephrotoxicity BUN, creatinine, urinalysis Hypokalemia Serum potassium Hypersensitivity reactions—rash, urticaria, eosinophilia Neuromuscular junction blockade Use with caution in patients receiving muscle relaxants Open table in a new tab

Protein and glycoprotein metabolism in brains of operantly conditioned pigeons

Pigeons were operantly conditioned to peck a lighted disc for food. Some were taught a red-green color discrimination, while others were overtrained to peck a white light only. The effect of training on metabolism in 35 subcellular fractions and nine chemical fractions from each brain was measured by uptake of [ 14C]glucosamine and [ 3H]valine injected 30 min prior to the final 30 min training session. Evidence for an effect of training upon uptake into discrete subcellular fractions was negligible. However, training decreased [ 3H]valine incorporation into one protein fraction significantly, and [ 14C]glucosamine incorporation into another fraction marginally. Furthermore, in the fraction which incorporated the greatest amount of [ 14C]glucosamine, naive and discrimination-trained birds took up more label than overtrained birds. These results confirm previous reports of metabolic changes correlated with training in selected protein and glycoprotein fractions from pigeon brain, but fail to localize the changes to specific anatomical sites or subcellular components. These findings support the view that the metabolites involved in the processing of behavioral information are chemically specific but broadly dispersed morphologically.

COLOR DISCRIMINATION IN THE CAT.

Red-green color discrimination by cats was demonstrated in a situation which effectively eliminated cues based on relative brightness. The persistence of the cat's response to cues based on brightness differences may help to account for the failure of previous experiments to show that cats can make behavioral color discriminations.