1
|
|
2
|
Rezende MTC, Figueiredo BGD, de Souza Bonifácio TA, Santos N, Andrade MJO. Variability of chromatic visual sensitivity: discrimination according to daily shifts. BIOL RHYTHM RES 2020. [DOI: 10.1080/09291016.2020.1837563] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Maria Thalita Cardoso Rezende
- Department of Psychology, Perception, Neurosciences and Behavior Laboratory, Federal University of Paraíba, João Pessoa, Brazil
| | | | | | - Natanael Santos
- Department of Psychology, Perception, Neurosciences and Behavior Laboratory, Federal University of Paraíba, João Pessoa, Brazil
| | - Michael Jackson Oliveirade Andrade
- Department of Psychology, Laboratory of Neuroscience, Chronobiology and Sleep Psychology, State University of Minas Gerais, Divinópolis, Brazil
| |
Collapse
|
3
|
Fernandes TMP, Andrade SM, de Andrade MJO, Nogueira RMTBL, Santos NA. Colour discrimination thresholds in type 1 Bipolar Disorder: a pilot study. Sci Rep 2017; 7:16405. [PMID: 29180712 PMCID: PMC5703961 DOI: 10.1038/s41598-017-16752-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Accepted: 11/16/2017] [Indexed: 11/09/2022] Open
Abstract
Although some studies have reported perceptual changes in psychosis, no definitive conclusions have been drawn about visual disturbances that are related to bipolar disorder (BPD). The purpose of the present study was to evaluate colour vision in BPD patients. Data were recorded from 24 participants: healthy control group (n = 12) and type 1 BPD group (n = 12). The participants were 20-45 years old and they were free from neurological disorders and identifiable ocular disease and had normal or corrected-to-normal visual acuity. Colour discrimination was evaluated using the Lanthony D-15d, Trivector and Ellipse tests, using a psychophysical forced-choice method. The relationship of visual measures to mood state and cognitive function was also investigated. The results showed that BPD patients had higher colour discrimination thresholds in the D15d (p < 0.001), Trivector (p < 0.001) and Ellipse (p < 0.01) tests compared with healthy controls. Linear regression analysis showed that mood state was related to colour discrimination. BPD individuals were not impaired in cognitive tasks. The present study provided new evidence of potential links between type 1 BPD and visual processing impairments. This research suggests a new direction for studies and the need for research in this field of study.
Collapse
Affiliation(s)
- Thiago Monteiro Paiva Fernandes
- Cognitive Neuroscience and Behaviour Program, Federal University of Paraiba, Joao Pessoa, Brazil.
- Perception, Neuroscience and Behaviour Laboratory, Federal University of Paraiba, Joao Pessoa, Brazil.
| | - Suellen Marinho Andrade
- Cognitive Neuroscience and Behaviour Program, Federal University of Paraiba, Joao Pessoa, Brazil
| | | | | | - Natanael Antonio Santos
- Cognitive Neuroscience and Behaviour Program, Federal University of Paraiba, Joao Pessoa, Brazil
- Perception, Neuroscience and Behaviour Laboratory, Federal University of Paraiba, Joao Pessoa, Brazil
| |
Collapse
|
4
|
Zachi EC, Costa TL, Barboni MTS, Costa MF, Bonci DMO, Ventura DF. Color Vision Losses in Autism Spectrum Disorders. Front Psychol 2017; 8:1127. [PMID: 28713324 PMCID: PMC5492848 DOI: 10.3389/fpsyg.2017.01127] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Accepted: 06/19/2017] [Indexed: 02/04/2023] Open
Abstract
Autism spectrum disorders (ASDs) are neurodevelopmental conditions characterized by impairments in social/communication abilities and restricted behaviors. The present study aims to examine color vision discrimination in ASD children and adolescents without intellectual disability. The participants were also subdivided in order to compare color vision thresholds of autistic participants and those who achieved diagnostic criteria for Asperger Syndrome (AS). Nine subjects with autism, 11 participants with AS and 36 typically developing children and adolescents participated in the study. Color vision was assessed by the Cambridge Color Test (CCT). The Trivector protocol was administered to determine color discrimination thresholds along the protan, deutan, and tritan color confusion lines. Data from ASD participants were compared to tolerance limits for 90% of the population with 90% probability obtained from controls thresholds. Of the 20 ASD individuals examined, 6 (30%) showed color vision losses. Elevated color discrimination thresholds were found in 3/9 participants with autism and in 3/11 AS participants. Diffuse and tritan deficits were found. Mechanisms for chromatic losses may be either at the retinal level and/or reflect reduced cortical integration.
Collapse
Affiliation(s)
- Elaine C. Zachi
- Department of Experimental Psychology, Nucleus for Neuroscience and Behavior, Institute of Psychology, University of São PauloSão Paulo, Brazil
| | - Thiago L. Costa
- Department of Experimental Psychology, Nucleus for Neuroscience and Behavior, Institute of Psychology, University of São PauloSão Paulo, Brazil
- Cognitive Neuroscience Laboratory and Developmental Disorders Program, Center for Health and Biological Sciences, Mackenzie Presbyterian UniversitySão Paulo, Brazil
| | - Mirella T. S. Barboni
- Department of Experimental Psychology, Nucleus for Neuroscience and Behavior, Institute of Psychology, University of São PauloSão Paulo, Brazil
| | - Marcelo F. Costa
- Department of Experimental Psychology, Nucleus for Neuroscience and Behavior, Institute of Psychology, University of São PauloSão Paulo, Brazil
| | - Daniela M. O. Bonci
- Department of Experimental Psychology, Nucleus for Neuroscience and Behavior, Institute of Psychology, University of São PauloSão Paulo, Brazil
| | - Dora F. Ventura
- Department of Experimental Psychology, Nucleus for Neuroscience and Behavior, Institute of Psychology, University of São PauloSão Paulo, Brazil
| |
Collapse
|
5
|
Fernandes TMDP, Almeida NL, Dos Santos NA. Comparison of color discrimination in chronic heavy smokers and healthy subjects. F1000Res 2017; 6:85. [PMID: 28928940 PMCID: PMC5580434 DOI: 10.12688/f1000research.10714.3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 08/01/2017] [Indexed: 11/20/2022] Open
Abstract
Background: Cigarette smoke is probably the most significant source of exposure to toxic chemicals for humans, involving health-damaging components, such as nicotine, hydrogen cyanide and formaldehyde. The aim of the present study was to assess the influence of chronic heavy smoking on color discrimination (CD). Methods: All subjects were free of any neuropsychiatric disorder, identifiable ocular disease and had normal acuity. No abnormalities were detected in the fundoscopic examination and in the optical coherence tomography exam. We assessed color vision for healthy heavy smokers ( n = 15; age range, 20-45 years), deprived smokers ( n = 15, age range 20-45 years) and healthy non-smokers ( n = 15; age range, 20-45 years), using the psychophysical forced-choice method. All groups were matched for gender and education level. In this test, the volunteers had to choose the pseudoisochromatic stimulus containing a test frequency at four directions (e.g., up, down, right and left) in the subtest of Cambridge Colour Test (CCT): Trivector. Results: Performance on CCT differed between groups, and the observed pattern was that smokers had lower discrimination compared to non-smokers. In addition, deprived smokers presented lower discrimination to smokers and non-smokers. Contrary to expectation, the largest differences were observed for medium and long wavelengths. Conclusions: These results suggests that cigarette smoking, chronic exposure to its compounds, and withdrawal from nicotine affect color discrimination. This highlights the importance of understanding the diverse effects of nicotine on attentional bias.
Collapse
Affiliation(s)
| | | | - Natanael Antonio Dos Santos
- Department of Psychology, Federal University of Paraiba, Joao Pessoa, Brazil.,Perception, Neuroscience and Behavior Laboratory, Federal University of Paraíba, Joao Pessoa, Brazil
| |
Collapse
|
6
|
Gene therapy for red-green colour blindness in adult primates. Nature 2009; 461:784-7. [PMID: 19759534 PMCID: PMC2782927 DOI: 10.1038/nature08401] [Citation(s) in RCA: 203] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2009] [Accepted: 08/14/2009] [Indexed: 01/09/2023]
Abstract
Red-green colour blindness, which results from the absence of either the long- (L) or middle- (M) wavelength-sensitive visual photopigments, is the most common single locus genetic disorder. Here, the possibility of curing colour blindness using gene therapy was explored in experiments on adult monkeys that had been colour blind since birth. A third type of cone pigment was added to dichromatic retinas, providing the receptoral basis for trichromatic colour vision. This opened a new avenue to explore the requirements for establishing the neural circuits for a new dimension of colour sensation. Classic visual deprivation experiments1 have led to the expectation that neural connections established during development would not appropriately process an input that was not present from birth. Therefore, it was believed that treatment of congenital vision disorders would be ineffective unless administered to the very young. Here, however, addition of a third opsin in adult red-green colour-deficient primates was sufficient to produce trichromatic colour vision behaviour. Thus, trichromacy can arise from a single addition of a third cone class and it does not require an early developmental process. This provides a positive outlook for the potential of gene therapy to cure adult vision disorders.
Collapse
|
7
|
Tait DM, Carroll J. Normality of colour vision in a compound heterozygous female carrying protan and deutan defects. Clin Exp Optom 2009; 92:356-61. [PMID: 19473349 DOI: 10.1111/j.1444-0938.2009.00359.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND Inherited red-green colour vision defects are quite common, affecting one in 12 males, but are less common in women, affecting about one in 250. Because red-green defects are X-linked, nearly 15 per cent of females are heterozygous carriers of red-green colour deficiency. In addition, about one in 150 females are 'double carriers', where both of their X chromosomes have L/M gene arrays encoding a red-green defect. If a woman carries the same type of colour vision defect on each X-chromosome, she will be red-green colour deficient, whereas if she carries opposing defects (protan versus deutan) on each X chromosome, she will have normal colour vision, owing to the process of X-inactivation. These women are referred to as compound heterozygotes, though very few have been reported. Questions remain about whether the colour vision capacity of these women is comparable to that of 'normal' trichromats. METHODS We examined a compound heterozygote carrier of both protanopia and deuteranomaly. We also examined male members of her family representing both forms of red-green defect carried by the female proband. Complete colour vision testing was done, including Rayleigh matches, pseudoisochromatic plates, unique hue measurements and 100-Hue tests. Flicker-photometric ERG estimates of L : M cone ratio were obtained, as were Medmont C100 settings. RESULTS Genetic analyses provided direct confirmation of compound heterozygosity. The compound heterozygote showed Schmidt's sign, consistent with an extreme skew in her L : M cone ratio and usually associated with protan carrier status. CONCLUSION Apart from Schmidt's sign, we found the colour vision of the compound heterozygote to be indistinguishable from that of a normal trichromat.
Collapse
Affiliation(s)
- Diane M Tait
- Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | | |
Collapse
|
8
|
Kuchenbecker J, Röhl FW, Wesselburg A, Bernarding J, Behrens-Baumann W. Untersuchungen zur Validität eines webbasierten Farbsehtests für Screeninguntersuchungen des Farbensehens. Ophthalmologe 2007; 104:47-53. [PMID: 17160379 DOI: 10.1007/s00347-006-1443-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
BACKGROUND With standardized examination conditions, a web-based color vision test using pseudoisochromatic color plates can deliver test results comparable to those yielded by conventional color vision tests. The aim of the study is to analyze to what extent a web-based color vision test can be used as a screening test on the internet after visual monitor calibration. METHODS A German-language web-based color vision test with 25 pseudoisochromatic color plates based on the color plates of Velhagen and Broschmann and of Ishihara was developed, which can be seen at http://www.farbsehtest.de. Volunteers were recruited by means of specific information distributed on the internet, in various print media, and on the radio. RESULTS Over a period of 12 months, 2,126 of the initial volunteers [541 women and 1,588 men; mean age 34.27 (+/-14.1) years] with a valid test result for 25 color plates performed the web-based color vision test, 1,700 (506 women and 1,194 men) of whom passed it. Of the 426 volunteers who did not pass the test, 32 were women and 394, men. Counter-testing was performed on 101 volunteers (34 women and 67 men) with a mean age of 36.74 (+/-11.6) years. CONCLUSIONS The results recorded in the patients who underwent counter-testing suggest that, if handled correctly, the web-based color vision test can be used as a color vision screening test on the internet.
Collapse
Affiliation(s)
- J Kuchenbecker
- Augenklinik des Helios-Klinikums Berlin-Buch, Karower Str. 11, 13125, Berlin, Germany.
| | | | | | | | | |
Collapse
|
9
|
Mancuso K, Neitz M, Neitz J. An adaptation of the Cambridge Colour Test for use with animals. Vis Neurosci 2006; 23:695-701. [PMID: 16962014 DOI: 10.1017/s0952523806233364] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2006] [Accepted: 02/10/2006] [Indexed: 11/06/2022]
Abstract
Recently, molecular biological techniques have presented new opportunities for addressing questions concerning the neural mechanisms involved in color coding, thereby rousing renewed interest in animal color vision testing. We have modified a computer-based assessment tool, the Cambridge Colour Test, to make it suitable for use with animals. Here, the validity and reliability of the testing method were evaluated using squirrel monkeys. Because the chromatic stimuli and the achromatic backgrounds of the test consist of dots that vary in lightness, the stimulus parameters can be adjusted so that animals are not able to use luminance differences to make correct discriminations. Thus, in contrast to methods used previously, this test does not require that time be spent equating the luminance of each chromatic stimulus examined. Furthermore, the computer video-display based design of the testing apparatus can be easily replicated and adapted for use with many species in a variety of settings. In the present experiments, the squirrel monkeys' behavioral results agreed with the predictions for their color vision based on genetic analysis and electroretinography (ERG) spectral sensitivity data. Repeated measurements were highly consistent. Thus, an adaptation of the Cambridge Colour Test provides a valid and reliable method for testing color vision in animals.
Collapse
|
10
|
Gomes BD, Souza GS, Rodrigues AR, Saito CA, Silveira LCL, da Silva Filho M. Normal and dichromatic color discrimination measured with transient
visual evoked potential. Vis Neurosci 2006; 23:617-27. [PMID: 16962005 DOI: 10.1017/s0952523806233194] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2005] [Accepted: 12/23/2005] [Indexed: 11/06/2022]
Abstract
It would be informative to have an electrophysiological method to
study, in an objective way, the effects of mercury exposure and other
neurotoxics on human color vision performance. The purpose of the present
work was to study human color discrimination by measuring chromatic
difference thresholds with visual evoked potential (VEP). Six young normal
trichromats (24 ± 1 years old) and one deutan (26 years old) were
tested. The stimuli consisted of sinusoidal isoluminant chromatic gratings
made from chromaticity pairs located along four different color directions
centered on two reference points. Heterochromatic flicker photometry (HFP)
protocol was used to obtain the isoluminance condition for every subject
and for all chromaticity pairs. Spatial frequency was 2 cycles/deg.
Presentation mode comprised onset (300 ms)/offset (700 ms) periods. As
previously described, we found a negative deflection in the VEP which was
related to the chromatic difference: as chromatic difference increased,
amplitude increased and latency decreased. VEP response amplitude was
plotted against distance in the CIE 1976 color space between the grating
chromaticities and fitted with a regression line. We found color
thresholds by extrapolating the fitting to null amplitude values. The
thresholds were plotted in the CIE 1976 color space as MacAdam ellipses.
In normal trichromats the ellipses had small size, low ellipticity, and
were vertically oriented. In the deutan subject, the ellipses had large
size, high ellipticity, and were oriented towards the deutan copunctal
locus. The VEP thresholds were similar to those obtained using grating
stimuli and psychophysical procedures, however smaller than those obtained
using pseudoisochromatic stimuli (Mollon-Reffin method). We concluded that
transient VEP amplitude as a function of contrast can be reliably used in
objective studies of chromatic discrimination performance in normal and
altered human subjects.
Collapse
Affiliation(s)
- Bruno D Gomes
- Departamento de Fisiologia, Universidade Federal do Pará, Pará, Brazil
| | | | | | | | | | | |
Collapse
|
11
|
Schupp C, Olano-Martin E, Gerth C, Morrissey BM, Cross CE, Werner JS. Lutein, zeaxanthin, macular pigment, and visual function in adult cystic fibrosis patients. Am J Clin Nutr 2004; 79:1045-52. [PMID: 15159235 PMCID: PMC2603302 DOI: 10.1093/ajcn/79.6.1045] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Pancreatic insufficiency in cystic fibrosis (CF), even with replacement pancreatic enzyme therapy, is often associated with decreased carotenoid absorption. Because the macular pigment of the retina is largely derived from 2 carotenoids, lutein and zeaxanthin, the decreased serum concentrations seen in CF may have consequences for ocular and retinal health OBJECTIVES Our aims were to determine plasma carotenoid concentrations, determine absorption and distribution of macular pigment, and assess retinal health and visual function in CF patients. DESIGN In 10 adult CF patients (ages 21-47 y) and 10 age- and sex-matched healthy control subjects, we measured macular pigment density in vivo, measured serum lutein and zeaxanthin concentrations, and comprehensively assessed visual performance (including contrast sensitivity, color discrimination, and retinal function) under conditions of daylight illumination. RESULTS Serum lutein and zeaxanthin were significantly reduced (P < 0.005) in CF patients ( +/- SD: 87 +/- 36.1 and 27 +/- 15.8 nmol/L, respectively) compared with control subjects (190 +/- 72.1 and 75 +/- 23.6 nmol/L, respectively). Although macular pigment optical density was significantly lower (P < 0.0001) in the CF group (0.24 +/- 0.11) than in the control group (0.53 +/- 0.12), no significant differences in visual function were observed. CONCLUSIONS Adults with CF have dramatically low serum and macular concentrations of carotenoids (lutein and zeaxanthin), but their ocular status and visual function are surprisingly good. The clinical implications of low plasma concentrations of carotenoids in CF are yet to be clarified.
Collapse
Affiliation(s)
- Christine Schupp
- Department of Ophthalmology, School of Medicine, University of California, Davis, USA
| | | | | | | | | | | |
Collapse
|
12
|
Flanagan P, Zele AJ. Chromatic and luminance losses with multiple sclerosis and optic neuritis measured using dynamic random luminance contrast noise. Ophthalmic Physiol Opt 2004; 24:225-33. [PMID: 15130171 DOI: 10.1111/j.1475-1313.2004.00191.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We measured thresholds for detecting changes in colour and in luminance contrast in observers with multiple sclerosis (MS) and/or optic neuritis (ON) to determine whether reduced sensitivity occurs principally in red-green or blue-yellow second-stage chromatic channels or in an achromatic channel. Colour thresholds for the observers with MS/ON were higher in the red-green direction than in the blue-yellow direction, indicating greater levels of red-green loss than blue-yellow loss. Achromatic thresholds were raised less than either red-green or blue-yellow thresholds, showing less luminance-contrast loss than chromatic loss. With the MS/ON observers, blue-yellow and red-green thresholds were positively correlated but increasing impairment was associated with more rapid changes in red-green thresholds than blue-yellow thresholds. These findings indicate that demyelinating disease selectively reduces sensitivity to colour vision over luminance vision and red-green colours over blue-yellow colours.
Collapse
Affiliation(s)
- Patrick Flanagan
- Department of Psychology, Deakin University, Victoria 3217, Australia.
| | | |
Collapse
|
13
|
Abstract
A vector model of colour contrast is examined in a colour space that is a logarithmic transformation of the MacLeod-Boynton cone-excitation diagram. Observers set matches in a haploscopic display, in which one eye viewed a standard display (a neutral target square in a coloured surround) and the other viewed a matching display (a variable square in its own surround). Contrast colours are simply represented in this colour space: the vector connecting the right-eye surround and matched chromaticities is parallel to and to the same length and direction as the vector that connects the left-eye (standard) surround and square chromaticities. This describes observers' matches to the hues induced in a neutral square for a range of inducing surround colours, a range of right-eye (match) surround colours and four different luminance contrasts.
Collapse
Affiliation(s)
- A J Shepherd
- Medical Research Council Applied Psychology Unit, Cambridge, UK.
| |
Collapse
|
14
|
|
15
|
The relative salience of the cardinal axes of colour space in normal and anomalous trichromats. DOCUMENTA OPHTHALMOLOGICA PROCEEDINGS SERIES 1997. [DOI: 10.1007/978-94-011-5408-6_27] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
|
16
|
|
17
|
Barbur JL, Harlow AJ, Plant GT. Insights into the different exploits of colour in the visual cortex. Proc Biol Sci 1994; 258:327-34. [PMID: 7886066 DOI: 10.1098/rspb.1994.0181] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
A new method that allows controlled masking of luminance contrast has been developed to study the use of chromatic signals in human vision. The method also makes it possible to examine the different uses of chromatic signals (e.g. the generation of perceived colour, or the construction and representation of object structure and form). By using this technique, we studied the threshold detection of chromatic signals in normal trichromats. The results show that chromatic signals are virtually unaffected by ongoing, randomly varying, luminance contrast changes. These findings suggest that chromatic signals are either processed independently or can be separated completely from any confounding luminance contrast components in the stimulus. Thresholds for detection of colour changes only, and for extraction of stimulus structure from chromatic signals in normal trichromats, in subjects with single cone receptor deficiency (i.e. dichromats) and in three subjects with abnormal colour vision caused by bilateral damage to ventromedial, extra-striate visual cortex (i.e. subjects with cerebral achromatopsia) have also been measured. No significant difference in thresholds for the two conditions was observed either in normal trichromats or in dichromats. Subjects with cerebral achromatopsia, however, reveal markedly different thresholds. The results suggest that chromatic signals are processed independently to generate perceived object colour or to construct spatially structured objects, and that these functions involve different neural substrates. The results help to explain, at least in part, why cerebral achromatopsia is a heterogeneous disorder, and why there can be significant differences in the effective use of chromatic signals in subjects described as cerebral achromatopsics.
Collapse
Affiliation(s)
- J L Barbur
- Applied Vision Research Centre, City University, London, U.K
| | | | | |
Collapse
|
18
|
Abstract
The Ishihara plates are widely used as a test for colour vision. Originally designed for the purpose of detecting congenital red-green colour blindness, the test also has some value in demonstrating acquired colour vision defects. There are, however, several disadvantages in the present arrangement of the plates. A modification of the test, involving the rearrangement of the order of the plates, is presented which, together with a new recording chart, simplifies both the administration and the interpretation of the test.
Collapse
|
19
|
|