Uniform trichromacy in Alouatta caraya and Alouatta seniculus: behavioural and genetic colour vision evaluation

Primate colour vision depends on a matrix of photoreceptors, a neuronal post receptoral structure and a combination of genes that culminate in different sensitivity through the visual spectrum. Along with a common cone opsin gene for short wavelengths (sws1), Neotropical primates (Platyrrhini) have only one cone opsin gene for medium-long wavelengths (mws/lws) per X chromosome while Paleotropical primates (Catarrhini), including humans, have two active genes. Therefore, while female platyrrhines may be trichromats, males are always dichromats. The genus Alouatta is inferred to be an exception to this rule, as electrophysiological, behavioural and molecular analyses indicated a potential for male trichromacy in this genus. However, it is very important to ascertain by a combination of genetic and behavioural analyses whether this potential translates in terms of colour discrimination capability. We evaluated two howler monkeys (Alouatta spp.), one male A. caraya and one female A. seniculus, using a combination of genetic analysis of the opsin gene sequences and a behavioral colour discrimination test not previously used in this genus. Both individuals completed the behavioural test with performances typical of trichromatic colour vision and the genetic analysis of the sws1, mws, and lws opsin genes revealed three different opsin sequences in both subjects. These results are consistent with uniform trichromacy in both male and female, with presumed spectral sensitivity peaks similar to Catarrhini, at ~ 430 nm, 532 nm, and 563 nm for S-, M- and L-cones, respectively.

Ganglion cells and displaced amacrine cells density in the retina of the collared peccary (Pecari tajacu)

In the present study, we investigated the topographical distribution of ganglion cells and displaced amacrine cells in the retina of the collared peccary (Pecari tajacu), a diurnal neotropical mammal of the suborder Suina (Order Artiodactyla) widely distributed across central and mainly South America. Retinas were prepared and processed following the Nissl staining method. The number and distribution of retinal ganglion cells and displaced amacrine cells were determined in six flat-mounted retinas from three animals. The average density of ganglion cells was 351.822 ± 31.434 GC/mm². The peccary shows a well-developed visual streak. The average peak density was 6,767 GC/mm² and located within the visual range and displaced temporally as an area temporalis. Displaced amacrine cells have an average density of 300 DAC/mm², but the density was not homogeneous along the retina, closer to the center of the retina the number of cells decreases and when approaching the periphery the density increases, in addition, amacrine cells do not form retinal specialization like ganglion cells. Outside the area temporalis, amacrine cells reach up to 80% in the ganglion cell layer. However, in the region of the area temporalis, the proportion of amacrine cells drops to 32%. Thus, three retinal specializations were found in peccary’s retina by ganglion cells: visual streak, area temporalis and dorsotemporal extension. The topography of the ganglion cells layer in the retina of the peccary resembles other species of Order Artiodactyla already described and is directly related to its evolutionary history and ecology of the species.

Comparison of Visual Functions of Two Amazonian Populations: Possible Consequences of Different Mercury Exposure

The present study investigated the visual perimetry and color vision of two Amazonian populations differently exposed to mercury. Ten riverines environmentally exposed to mercury by fish eating and 34 gold-miners occupationally exposed to mercury vapor. The visual perimetry was estimated using the Förster perimeter and the color vision was evaluated using a computerized version of Farnsworth-Munsell test. Riverine and gold-miners' hair mercury concentrations were quantified. Mercury hair concentration of the riverines was significantly higher than that from gold-miners. Riverines had lower perimetric area than the gold-miners. The errors in the hue ordering test of both Amazonian populations were larger than the controls (non-exposed subjects), but there was no difference between themselves. Riverines had significant multiple association between the visual function and hair mercury concentration, while the gold-miners has no significant association with the exposure. We concluded that the different ways of mercury exposure led to similar visual outcomes, with greater impairment in riverines (organic mercury exposed subjects).

A proposed correction in the weighted method to score the Ishihara test

Objective

Ishihara test is a color vision test, whose results consider that all plates of the test have the same weighting. Rodriguez-Carmona et al. (Aviat Space Environ Med 83:19–29, 2012) proposed an equation to quantify the Ishihara test results (severity index), which took an account the rate of hits from the different plates of the test considering the performance of trichromat or colorblind population. We proposed a correction in Rodiguez-Carmona’s equation for the severity index. We evaluated 60 normal trichromats and 107 subjects with congenital color deficiency. We calculated three indexes to quantify the results of each subject: a non-weighted index, a weighted index similar to the Rodriguez-Carmona et al., and a weighted index modified which combined the hit frequency for each plate in a trichromat population and of the error reading frequency for each plate in color-blind populations.

Results

Compared to the non-weighted evaluation, the weighted index was reduced by 22.95%, 32.92%, and 35.38% from trichromats, protan and deutan groups, respectively. Receiver Operating Characteristics (ROC) analysis showed perfect performance of the classifier for all metrics to measure the Ishihara test results. The proposal correction changed significantly the value of the index, but the overall benefits were small.

Electronic supplementary material

The online version of this article (10.1186/s13104-019-4320-2) contains supplementary material, which is available to authorized users.

Psychophysical Evaluation of Visual Functions of Ex-Alcoholic Subjects After Prolonged Abstinence

Chronic alcohol abuse can lead to a brain damages, and the health status of alcoholics even after a long-term alcohol abstinence is a public health concern. The present study investigated the color vision and spatial luminance contrast sensitivity of a group of 17 ex-alcoholics (46.3 ± 6.7 years old) in long-term alcohol abstinence after having been previously under alcohol dependence for many years. We also investigated the association of impaired psychophysical performance in different tests we applied. The mean time of alcohol consumption was 16.9 ± 5.1 years and the mean abstinence period was 12.4 ± 8.5 years. Achromatic vision of all subjects was evaluated using spatial luminance contrast sensitivity function (CSF) test and color vision was evaluated using Mollon–Reffin color discrimination test (MR) and the Farnsworth–Munsell 100 hue arrangement test (FM100). Relative to controls, the spatial luminance contrast sensitivity was lower in 10/17 of the ex-alcoholic subjects. In the color vision tests, 11/16 ex-alcoholic subjects had impaired results compared to controls in the FM100 test and 13/14 subjects had color vision deficits measured in the MR test. Fourteen subjects performed all visual tests, three subjects had impaired results for all tests, seven subjects had impaired results in two tests, three subjects had visual deficit in one test, and one had normal results for all tests. The results showed the existence of functional deficits in achromatic and chromatic vision of subjects with history of chronic alcoholism after long abstinence. Most subjects had altered result in more than one test, especially in the color vision tests. The present investigation suggests that the damage in visual functions produced by abusive alcohol consumption is not reversed after long term alcohol abstinence.

Pathway-specific light adaptation in human electroretinograms

The cellular origins of slow ERG changes during light adaptation following a dark-adapted state are still unclear. To study light adaptation, six healthy, normal trichromats were dark-adapted for 30 min prior to full-field ERG recordings to sinusoidal stimuli that isolate responses of the L- or M-cones or that stimulate luminance and chromatic mechanisms at 12 or 36 Hz. Recordings were performed for 16 min with 2-min intervals after onset of a constant background. Generally, the responses were sine-wave-like, and the first harmonic (fundamental) component dominated the Fourier spectrum except for the 12-Hz luminance stimulus in which two components, a sine-wave-like component and a transient component, determined the response profiles, leading to large second harmonic components. The amplitude of the first harmonic component (F) increased as a function of the light-adaptation time except for the 12-Hz luminance stimulus at which the F component decreased as a function of the light-adaptation period. The phase of the first harmonic component changed only slightly (less than 30°) during the light-adaptation period for all stimuli conditions. The L/M ratio in luminance reflecting ERGs decreased with increasing adaptation time. Our present data suggest that the light-adaptation process mainly reflects changes in the luminance pathway. The responses to 12-Hz luminance stimuli are determined by two different luminance driven pathways with different adaptation characteristics.

Teores de mercúrio em cabelo e consumo de pescado de comunidades ribeirinhas na Amazônia brasileira, região do Tapajós

Resumo Comunidades ribeirinhas estão expostas ao mercúrio devido à dieta composta por elevada ingestão de peixes. Com o objetivo de avaliar os níveis de exposição na região do Tapajós, identificando também a frequência de ingestão de pescado, realizou-se um estudo em adultos residentes nas comunidades ribeirinhas do município de Itaituba/PA. Foram coletadas amostras de cabelo para a determinação de mercúrio total e dados de frequência semanal de ingestão de peixes. A concentração média de mercúrio total variou de 7,25µg/g (em 2013) para 10,80µg/g (em 2014), não sendo observada diferença significativa (p = 0,1436). Quanto à frequência de ingestão de pescado, a maioria dos indivíduos avaliados apresentou um alto consumo, tanto em 2013 quanto em 2014. Índices elevados de mercúrio total foram observados somente naqueles com alto consumo de pescado em ambos anos. Ressalta-se a importância da continuação do monitoramento dos níveis de exposição em humanos, fundamentando-se nos índices de tolerância de 6µg/g preconizado pela Organização Mundial de Saúde, e na investigação quanto ao consumo de peixes para que as estratégias de controle e prevenção sejam melhoradas.

Influence of Spatial and Chromatic Noise on Luminance Discrimination

Pseudoisochromatic figures are designed to base discrimination of a chromatic target from a background solely on the chromatic differences. This is accomplished by the introduction of luminance and spatial noise thereby eliminating these two dimensions as cues. The inverse rationale could also be applied to luminance discrimination, if spatial and chromatic noise are used to mask those cues. In this current study estimate of luminance contrast thresholds were conducted using a novel stimulus, based on the use of chromatic and spatial noise to mask the use of these cues in a luminance discrimination task. This was accomplished by presenting stimuli composed of a mosaic of circles colored randomly. A Landolt-C target differed from the background only by the luminance. The luminance contrast thresholds were estimated for different chromatic noise saturation conditions and compared to luminance contrast thresholds estimated using the same target in a non-mosaic stimulus. Moreover, the influence of the chromatic content in the noise on the luminance contrast threshold was also investigated. Luminance contrast threshold was dependent on the chromaticity noise strength. It was 10-fold higher than thresholds estimated from non-mosaic stimulus, but they were independent of colour space location in which the noise was modulated. The present study introduces a new method to investigate luminance vision intended for both basic science and clinical applications.

Heart rate variability in multibacillar leprosy: Linear and nonlinear analysis

Objective

To evaluate the heart rate variability (HRV) in patients with multibacillary leprosy using dynamic linear and nonlinear analysis.

Material and methods

Twenty-one leprosy patients (mean age: 39.14 ±10.58 years) and 21 healthy subjects (mean age: 36.24 ± 12.64 years) completed the sample. Heart rate variability recording was performed by a Polar RS800 CX heart monitor during a period of 15 min in the supine position and 15 min in a sitting position. Analysis of HRV was performed by frequency domain from high frequency (HF) and low frequency (LF) spectral indexes in absolute and normalized units. The nonlinear analysis of HRV was calculated using symbolic analysis (0V%, 1V%, 2LV% and 2UV% indexes), Shannon entropy (SE) and normalized complexity index (NCI).

Results

Linear analysis: both groups showed higher HF values (p < 0.05) and smaller LF values (p < 0.05) in supine than in sitting position. The leprosy patients showed higher LF values (p < 0.05) and smaller HF values (p < 0.05) compared to the controls on supine position. Symbolic analysis: leprosy patients had higher 0V% values (p < 0.05), smaller 2LV% values (p < 0.05) and 2UV % values compared to healthy subjects on both positions. The 1V % had higher values (p < 0.05) for leprosy patients than for controls in the sitting position. The control subjects had smaller 0V % values (p < 0.05), and higher 2UV % values (p < 0.05) in the supine position compared to the sitting position. Leprosy patients had higher 2UV index values (p < 0.05) in the supine position compared to the sitting position. In the complexity analysis, leprosy patients had smaller SE and NCI values (p < 0.05) than the control in the supine position. There was no difference between the SE and NCI values of leprosy and the control subjects in the sitting position. The control subjects had higher SE and NCI values (p < 0.05) in the supine position than in the sitting position.

Conclusion

Leprosy patients had higher sympathetic modulation and smaller vagal modulation than controls, indicating less HRV and cardiac modulation with lower complexity. The control group displayed significant HRV differences in response to position changes while leprosy patients had fewer HRV differences after the same postural change. An analysis of HRV with linear and non-linear dynamics proved to be a reliable method and promising for the investigation of autonomic dysfunction in patients with multibacillary leprosy.

Manifestações emocionais e motoras de ribeirinhos expostos ao mercúrio na Amazônia

RESUMO: Introdução: A investigação dos impactos clínico-neurológicos associados às concentrações de exposição ao mercúrio em populações expostas é necessária na Amazônia. Objetivo: Analisar as manifestações emocionais e motoras de ribeirinhos expostos pela dieta nos municípios de Itaituba e Acará, ambos no Pará. Método: Foram coletadas amostras de cabelo para a determinação de mercúrio total (HgT), obtidos dados demográficos e sintomatológicos emocionais (depressão, ansiedade e insônia) e motores (parestesia, fraqueza muscular, desequilíbrio ao andar, tremor, dor nos membros e disartria). Resultados: A concentração mediana de HgT em Itaituba foi significativamente superior (p < 0,0001) àquela em Acará. As manifestações emocionais foram identificadas em 26 (26,5%) participantes de Itaituba e em 24 (52,2%) em Acará. Com relação às queixas motoras especificas, em Itaituba ocorreram em 63 (64,3%) voluntários, sendo mais referidas a dor nos membros (36,7%), a parestesia (32,6%) e a fraqueza muscular (27,5%). No Acará, 33 (71,7%) participantes apresentaram manifestações motoras, com o maior número queixando de parestesia (54,3%), dor nos membros (52,2%) e tremor (34,8%). As concentrações médias de HgT em Itaituba naqueles com manifestações emocionais e com manifestações motoras estiveram acima do considerado tolerável (6 µg/g) pela Organização Mundial de Saúde. Conclusão: Os resultados revelaram que a concentração de mercúrio nas manifestações emocionais e motoras de Itaituba são maiores do que nos ribeirinhos do Acará. Novos estudos são necessários com a aplicação de testes convencionais qualitativos e/ou quantitativos específicos, assim como também a investigação de outros sinais clínicos.

The intake of fish and the mercury concentration of fishing families at the city of Imperatriz (MA), Brazil

INTRODUCTION

Significant levels of mercury exposure associated with fish intake have been demonstrated in riverine populations living in areas of mineral exploration as the basin of Tapajós and Madeira. In the Tocantins region, although few studies, there is no evidence of human exposure through food.

OBJECTIVE

To assess the levels of exposure to mercury in resident fishermen families in the riverside area of the middle Tocantins and to quantify the levels in fish consumed by these families.

METHODS

We conducted a cross sectional study involving families of Beira Rio community fishermen, located on the Tocantins riverbanks in the city of Imperatriz, Maranhão. Brazil. Data were collected from socio demographic and food profile, as well as samples of fish and hair, which were analyzed by atomic absorption spectrophotometry.

RESULTS

The socio demographic profile of families studied was common to the local population located in other basins. The food profile did not run the default rule, with the fish being the primary dietary protein source. The species of piscivorous and zooplancton habits had the highest mercury concentrations, and the mean values were 0.2775 µg/g in fish dog and 0.1360 µg/g in mapará. Among the 25 families evaluated, the lowest average concentration of family was 0.186 ± 0.043 µg/g and the higher was 5.477 ± 2.896 µg/g.

CONCLUSION

Fishing families have low mercury exposure levels in the same order of magnitude, probably because of the food consumption of fish, including piscivorous species, which were found to be below the safe upper limit for human consumption established by Brazilian standards. This serves as a reference for other studies.

Psychophysical Evaluation of Congenital Colour Vision Deficiency: Discrimination between Protans and Deutans Using Mollon-Reffin's Ellipses and the Farnsworth-Munsell 100-Hue Test

We have used the Farnsworth-Munsell 100-hue (FM 100) test and Mollon-Reffin (MR) test to evaluate the colour vision of 93 subjects, 30.4 ± 9.7 years old, who had red-green congenital colour vision deficiencies. All subjects lived in Belém (State of Pará, Brazil) and were selected by the State of Pará Traffic Department. Selection criteria comprised the absence of visual dysfunctions other than Daltonism and no history of systemic diseases that could impair the visual system performance. Results from colour vision deficient were compared with those from 127 normal trichromats, 29.3 ± 10.3 years old. For the MR test, measurements were taken around five points of the CIE 1976 colour space, along 20 directions irradiating from each point, in order to determine with high-resolution the corresponding colour discrimination ellipses (MacAdam ellipses). Three parameters were used to compare results obtained from different subjects: diameter of circle with same ellipse area, ratio between ellipse’s long and short axes, and ellipse long axis angle. For the FM 100 test, the parameters were: logarithm of the total number of mistakes and positions of mistakes in the FM diagram. Data were also simultaneously analysed in two or three dimensions as well as by using multidimensional cluster analysis. For the MR test, Mollon-Reffin Ellipse #3 (u’ = 0.225, v’ = 0.415) discriminated more efficiently than the other four ellipses between protans and deutans once it provided larger angular difference in the colour space between protan and deutan confusion lines. The MR test was more sensitive than the FM 100 test. It separated individuals by dysfunctional groups with greater precision, provided a more sophisticated quantitative analysis, and its use is appropriate for a more refined evaluation of different phenotypes of red-green colour vision deficiencies.

Spectral Sensitivity Measured with Electroretinogram Using a Constant Response Method

A new method is presented to determine the retinal spectral sensitivity function S(λ) using the electroretinogram (ERG). S(λ)s were assessed in three different species of myomorph rodents, Gerbils (Meriones unguiculatus), Wistar rats (Ratus norvegicus), and mice (Mus musculus). The method, called AC Constant Method, is based on a computerized automatic feedback system that adjusts light intensity to maintain a constant-response amplitude to a flickering stimulus throughout the spectrum, as it is scanned from 300 to 700 nm, and back. The results are presented as the reciprocal of the intensity at each wavelength required to maintain a constant peak to peak response amplitude. The resulting S(λ) had two peaks in all three rodent species, corresponding to ultraviolet and M cones, respectively: 359 nm and 511 nm for mice, 362 nm and 493 nm for gerbils, and 362 nm and 502 nm for rats. Results for mouse and gerbil were similar to literature reports of S(λ) functions obtained with other methods, confirming that the ERG associated to the AC Constant-Response Method was effective to obtain reliable S(λ) functions. In addition, due to its fast data collection time, the AC Constant Response Method has the advantage of keeping the eye in a constant light adapted state.

Somatosensory Psychophysical Losses in Inhabitants of Riverside Communities of the Tapajós River Basin, Amazon, Brazil: Exposure to Methylmercury Is Possibly Involved

The purpose of this work was to evaluate the somatosensory system of methylmercury-exposed inhabitants living in the communities of the Tapajós river basin by using psychophysical tests and to compare with measurements performed in inhabitants of the Tocantins river basin. We studied 108 subjects from Barreiras and São Luiz do Tapajós, two communities of the Tapajós river basin, State of Pará, Amazon, Brazil, aged 13–53 years old. Mercury analysis was performed in head hair samples weighting 0.1–0.2 g by using atomic absorption spectrometry. Three somatosensory psychophysical tests were performed: tactile sensation threshold, vibration sensation duration, and two-point discrimination. Semmes-Weinstein 20 monofilaments with different diameters were used to test the tactile sensation in the lower lip, right and left breasts, right and left index fingers, and right and left hallux. The threshold was the thinner monofilament perceived by the subject. Vibration sensation was investigated using a 128 Hz diapason applied to the sternum, right and left radial sides of the wrist, and right and left outer malleoli. Two trials were performed at each place. A stopwatch recorded the vibration sensation duration. The two-point discrimination test was performed using a two-point discriminator. Head hair mercury concentration was significantly higher in mercury-exposed inhabitants of Tapajós than in non-exposed inhabitants of Tocantins (p < 0.01). When all subjects were divided in two groups independently of age—mercury-exposed and non-exposed—the following results were found: tactile sensation thresholds in mercury-exposed subjects were higher than in non-exposed subjects at all body parts, except at the left chest; vibration sensation durations were shorter in mercury-exposed than in non-exposed subjects, at all locations except in the upper sternum; two-point discrimination thresholds were higher in mercury-exposed than in non-exposed subjects at all body parts. There was a weak linear correlation between tactile sensation threshold and mercury concentration in the head hair samples. No correlation was found for the other two measurements. Mercury-exposed subjects had impaired somatosensory function compared with non-exposed control subjects. Long-term mercury exposure of riverside communities in the Tapajós river basin is a possible but not a definitely proven cause for psychophysical somatosensory losses observed in their population. Additionally, the relatively simple psychophysical measures used in this work should be followed by more rigorous measures of the same population.

Ganglion cell and displaced amacrine cell density distribution in the retina of the howler monkey (Alouatta caraya)

Unlike all other New World (platyrrine) monkeys, both male and female howler monkeys (Alouatta sp.) are obligatory trichromats. In all other platyrrines, only females can be trichromats, while males are always dichromats, as determined by multiple behavioral, electrophysiological, and genetic studies. In addition to obligatory trichromacy, Alouatta has an unusual fovea, with substantially higher peak cone density in the foveal pit than every other diurnal anthropoid monkey (both platyrrhines and catarrhines) and great ape yet examined, including humans. In addition to documenting the general organization of the retinal ganglion cell layer in Alouatta, the distribution of cones is compared to retinal ganglion cells, to explore possible relationships between their atypical trichromacy and foveal specialization. The number and distribution of retinal ganglion cells and displaced amacrine cells were determined in six flat-mounted retinas from five Alouatta caraya. Ganglion cell density peaked at 0.5 mm between the fovea and optic nerve head, reaching 40,700-45,200 cells/mm2. Displaced amacrine cell density distribution peaked between 0.5-1.75 mm from the fovea, reaching mean values between 2,050-3,100 cells/mm2. The mean number of ganglion cells was 1,133,000±79,000 cells and the mean number of displaced amacrine cells was 537,000±61,800 cells, in retinas of mean area 641±62 mm2. Ganglion cell and displaced amacrine cell density distribution in the Alouatta retina was consistent with that observed among several species of diurnal Anthropoidea, both platyrrhines and catarrhines. The principal alteration in the Alouatta retina appears not to be in the number of any retinal cell class, but rather a marked gradient in cone density within the fovea, which could potentially support high chromatic acuity in a restricted central region.

Scaling the primate lateral geniculate nucleus: niche and neurodevelopment in the regulation of magnocellular and parvocellular cell number and nucleus volume

New stereological assessments of lateral geniculate nucleus (LGN) neuron numbers and volumes in five New World primates (Cebus apella, Saguinus midas niger, Alouatta caraya, Aotus azarae, and Callicebus moloch) and compiled LGN volumes for an additional 26 mammals were analyzed for a better understanding of visual system evolution. Both the magnocellular (M)- and the parvocellular (P)-cell populations scale allometrically with brain volume in primates, P cells with a significantly higher slope such that, for every increase in M neuron number, P neuron numbers more than double (ln scale; y = 0.89x + 2.42R(2) = 0.664). In diurnal primates, the ratio of P to M cells was slightly but significantly higher than in nocturnal primates. For all mammals, including primates, LGN volume was unrelated to nocturnal or diurnal niche but showed marked differences in slope and intercept depending on taxonomic group. The allometric scaling of M and P cells can be related to the order of neurogenesis, with late-generated P cells increasing with positive allometry compared with the earlier-generated M cells. This developmental regularity links relative foveal representation to relative isocortex enlargement, which is also generated late. The small increase in the P/M cell ratio in diurnal primates may result from increased developmental neuron loss in the M-cell population as it competes for limited termination zones in primary visual cortex.

Life quality assessment of patients after phacoemulsification or extracapsular cataract extraction

PURPOSE

To study the quality of life, treatment outcomes, and satisfaction in patients who have undergone cataract surgery Methods: This comparative case series study was conducted at the Ophthalmology Service of the Bettina Ferro de Souza University Hospital, Belém, Pará, Brazil. Totally, 60 patients with cataract were included; 50% underwent conventional extracapsular cataract extraction (ECEE) and 50% underwent cataract extraction by phacoemulsification (PHACO). Patients were interviewed using the Visual Function 14 (VF-14) questionnaire to determine the quality of life before and 30 days after surgery. The results of ophthalmological examination were recorded in the patients' files and were available throughout this study. One-way ANOVA, Tukey's post-hoc comparison, and the sign test were used for statistical analyses.

RESULTS

The mean VF-14 satisfaction index was 38.0 and 89.4 before and after surgery, respectively, for the ECEE group and 47.0 and 94.1, respectively, for the PHACO group. The improvement in patient quality of life after surgery was significant in both groups (p<0.0001), with a similar amount of improvement in both groups.

CONCLUSIONS

The observed improvement in quality of life was significant (p<0.0001) and directly related to patient satisfaction with surgical outcomes, which was also significant (p<0.0001) as assessed using the VF-14. Satisfaction and quality of life are individual factors; consequently, patient responses to questions regarding improvements in the ability to perform each activity are subjective and depend uniquely on individual perception.

Monitoring mercury exposure in reproductive aged women inhabiting the Tapajós river basin, Amazon

Among Amazonian communities, exposure to methylmercury is associated mainly with fish consumption that may affect fetal development in pregnant women. Therefore a temporal assessment was performed to assess the exposure of reproductive aged women to mercury who reside in the riparian communities of São Luís do Tapajós and Barreiras located in the Tapajós basin of the Brazilian Amazon from 1999 to 2012. The total mercury concentration in the 519 hair samples was assessed by cold vapor atomic absorption spectrometry. Data analysis showed that the average total mercury concentration decreased from 1.066 to 0.743 μg/g in those years. In 1999 the proportion of volunteers with mercury levels ≥ 10 μg/g was approximately 68 %. In general, exposure to mercury decreased among women of reproductive age, but the potential risks to reproduction and human health is still an issue as 22 % of the woman continued showing high mercury levels (≥ 10 μg/g) in 2012.

[Neurological manifestations in riverine populations from areas exposed to mercury in the Brazilian Amazon]

This study evaluated current levels of mercury exposure and sensory symptoms in adults from three riverine communities in Pará State, Brazil, two of which located in the Tapajós River basin and one in the Tocantins basin. Participants in this study included 78 residents in Barreiras (Tapajós), 30 in São Luiz do Tapajós (Tapajós), and 49 in Furo do Maracujá (Tocantins). Total hair mercury concentrations were quantified by atomic absorption spectrophotometry, and neurological evaluation was conducted by routine examination. Mercury concentrations in the Tapajós communities were higher than those in the Tocantins (p < 0.01). Evaluation of neurological changes showed no significant difference between the communities in exposed areas and control areas for the changes observed by conventional neurological examination, except for gait deviation (p < 0.05). The study concludes that despite the mercury exposure levels, there was a low frequency of sensory alterations according to conventional neurological testing.

Joint entropy for space and spatial frequency domains estimated from psychometric functions of achromatic discrimination

We used psychometric functions to estimate the joint entropy for space discrimination and spatial frequency discrimination. Space discrimination was taken as discrimination of spatial extent. Seven subjects were tested. Gábor functions comprising unidimensionalsinusoidal gratings (0.4, 2, and 10 cpd) and bidimensionalGaussian envelopes (1°) were used as reference stimuli. The experiment comprised the comparison between reference and test stimulithat differed in grating's spatial frequency or envelope's standard deviation. We tested 21 different envelope's standard deviations around the reference standard deviation to study spatial extent discrimination and 19 different grating's spatial frequencies around the reference spatial frequency to study spatial frequency discrimination. Two series of psychometric functions were obtained for 2%, 5%, 10%, and 100% stimulus contrast. The psychometric function data points for spatial extent discrimination or spatial frequency discrimination were fitted with Gaussian functions using the least square method, and the spatial extent and spatial frequency entropies were estimated from the standard deviation of these Gaussian functions. Then, joint entropy was obtained by multiplying the square root of space extent entropy times the spatial frequency entropy. We compared our results to the theoretical minimum for unidimensional Gábor functions, 1/4π or 0.0796. At low and intermediate spatial frequencies and high contrasts, joint entropy reached levels below the theoretical minimum, suggesting non-linear interactions between two or more visual mechanisms. We concluded that non-linear interactions of visual pathways, such as the M and P pathways, could explain joint entropy values below the theoretical minimum at low and intermediate spatial frequencies and high contrasts. These non-linear interactions might be at work at intermediate and high contrasts at all spatial frequencies once there was a substantial decrease in joint entropy for these stimulus conditions when contrast was raised.

Multifocal electroretinography after high dose chloroquine therapy for malaria

PURPOSE

To investigate changes in multifocal electroretinography (mfERG) parameters associated with high dose chloroquine therapy for treatment of malaria in the Amazonia region of Brazil.

METHODS

Forty-eight subjects who had received chloroquine treatment for single or multiple malaria infections with a cumulative dose ranging from 1,050 to 27,000mg were included. The control group consisted of 37 healthy aged-matched subjects. Data was collected on amplitude and implicit time of the N1, P1 and N2 waves in the central macular hexagon (R1) and in five concentric rings at different retinal eccentricities (R2-R6).

RESULTS

No significant difference was observed in any mfERG parameter between chloroquine treated patients and control subjects. A comparison with previous data obtained from patients with rheumatologic disorders in the same region of Brazil who had received larger cumulative doses of chloroquine and had displayed mfERG changes, indicated that retinal toxicity seems to be dependent on cumulative dose.

CONCLUSION

Lack of mfERG changes in the current study suggests that intensive high dose chloroquine therapy for treatment of malaria is not associated with retinal toxicity.

Color discrimination in the tufted capuchin monkey, Sapajus spp

The present study evaluated the efficacy of an adapted version of the Mollon-Reffin test for the behavioral investigation of color vision in capuchin monkeys. Ten tufted capuchin monkeys (Sapajus spp., formerly referred to as Cebus apella) had their DNA analyzed and were characterized as the following: one trichromat female, seven deuteranope dichromats (six males and one female), and two protanope males, one of which was identified as an “ML protanope.” For their behavioral characterization, all of the subjects were tested at three regions of the Commission International de l'Eclairage (CIE) 1976 u′v′ diagram, with each test consisting of 20 chromatic variation vectors that were radially distributed around the chromaticity point set as the test background. The phenotypes inferred from the behavioral data were in complete agreement with those predicted from the genetic analysis, with the threshold distribution clearly differentiating between trichromats and dichromats and the estimated confusion lines characteristically converging for deuteranopes and the “classic” protanope. The discrimination pattern of the ML protanope was intermediate between protan and deutan, with confusion lines horizontally oriented and parallel to each other. The observed phenotypic differentiation confirmed the efficacy of the Mollon-Reffin test paradigm as a useful tool for evaluating color discrimination in nonhuman primates. Especially noteworthy was the demonstration of behavioral segregation between the “classic” and “ML” protanopes, suggesting identifiable behavioral consequences of even slight variations in the spectral sensitivity of M/L photopigments in dichromats.

Long-term occupational exposure to organic solvents affects color vision, contrast sensitivity and visual fields

The purpose of this study was to evaluate the visual outcome of chronic occupational exposure to a mixture of organic solvents by measuring color discrimination, achromatic contrast sensitivity and visual fields in a group of gas station workers. We tested 25 workers (20 males) and 25 controls with no history of chronic exposure to solvents (10 males). All participants had normal ophthalmologic exams. Subjects had worked in gas stations on an average of 9.6±6.2 years. Color vision was evaluated with the Lanthony D15d and Cambridge Colour Test (CCT). Visual field assessment consisted of white-on-white 24–2 automatic perimetry (Humphrey II-750i). Contrast sensitivity was measured for sinusoidal gratings of 0.2, 0.5, 1.0, 2.0, 5.0, 10.0 and 20.0 cycles per degree (cpd). Results from both groups were compared using the Mann–Whitney U test. The number of errors in the D15d was higher for workers relative to controls (p<0.01). Their CCT color discrimination thresholds were elevated compared to the control group along the protan, deutan and tritan confusion axes (p<0.01), and their ellipse area and ellipticity were higher (p<0.01). Genetic analysis of subjects with very elevated color discrimination thresholds excluded congenital causes for the visual losses. Automated perimetry thresholds showed elevation in the 9°, 15° and 21° of eccentricity (p<0.01) and in MD and PSD indexes (p<0.01). Contrast sensitivity losses were found for all spatial frequencies measured (p<0.01) except for 0.5 cpd. Significant correlation was found between previous working years and deutan axis thresholds (rho = 0.59; p<0.05), indexes of the Lanthony D15d (rho = 0.52; p<0.05), perimetry results in the fovea (rho = −0.51; p<0.05) and at 3, 9 and 15 degrees of eccentricity (rho = −0.46; p<0.05). Extensive and diffuse visual changes were found, suggesting that specific occupational limits should be created.

Visual Dysfunction of Type I and VI Mucopolysaccharidosis Patients Evaluated with Visual Evoked Cortical Potential

Purpose

To evaluate the visual system of patients suffering from type I or VI mucopolysaccharidosis (MPS) by recording the visual evoked cortical potential (VECP).

Methods

Two patients with MPS VI and 2 patients with MPS I were tested before and after enzyme replacement therapy (ERT). A control group of 20 subjects was tested for statistical comparison. VECP was elicited by monocular stimulation with 1-Hz phase-reversal checkerboard patterns at 0.5 and 2 cycles per degree and with 16° of visual field. In all patients, both eyes were tested. VECP amplitude and latency were measured and compared with tolerance limits obtained from controls.

Results

MPS I and VI patients have a severe visual impairment that can be quantified by measuring VECPs. Even after several weeks of ERT, the visual impairment remained unaltered, indicating that the treatment had no significant influence on the visual conditions of MPS patients. Visual responses to high spatial frequencies were more deeply impaired than responses to low spatial frequencies. This can be explained by the kind of damage in the visual system that preferentially targets the eye optics.

Conclusion

VECPs can be used to monitor the degree of visual impairment of MPS patients and to check ERT efficacy.

Avaliação visual de sujeitos expostos de forma ocupacional a solventes orgânicos através de métodos psicofísicos

Os solventes orgânicos são substâncias neurotóxicas que podem causar efeitos danosos sobre as funções visuais. É comum a exposição ocupacional a esses tipos de substâncias, pois elas apresentam grande aplicabilidade em inúmeras atividades. Os efeitos podem ser quantificados por testes psicofísicos. Os testes mais usados nesse tipo de avaliação são de ordenamento de matizes, como o Teste D15 Dessaturado de Lanthony e o Teste dos 100 Matizes de Farnsworth-Munsell, e avaliação de sensibilidade ao contraste espacial de luminância, como MCT 8000 Vistech, VCTS 6500 Vistech e FACT 101. Em geral esses testes descrevem perda de discriminação de cores, afetando tanto o eixo azul-amarelo quanto o eixo verde-vermelho, e diminuição da sensibilidade ao contraste de luminância principalmente para as frequências espaciais mais baixas. Existe correlação positiva entre os resultados da avaliação psicofísica e vários marcadores biológicos e ambientais, mas essa correlação depende do marcador e do tipo de solvente ao qual os indivíduos são expostos. Fatores como alcoolismo crônico e tabagismo inveterado podem interferir no processo de correlacionar esses resultados.

Métodos utilizados na avaliação psicofísica da visão de cores humana

A cor é um atributo perceptual que nos permite identificar e localizar padrões ambientais de mesmo brilho e constitui uma dimensão adicional na identificação de objetos, além da detecção de inúmeros outros atributos dos objetos em sua relação com a cena visual, como luminância, contraste, forma, movimento, textura, profundidade. Decorre daí a sua importância fundamental nas atividades desempenhadas pelos animais e pelos seres humanos em sua interação com o ambiente. A psicofísica visual preocupa-se com o estudo quantitativo da relação entre eventos físicos de estimulação sensorial e a resposta comportamental resultante desta estimulação, fornecendo dessa maneira meios de avaliar aspectos da visão humana, como a visão de cores. Este artigo tem o objetivo de mostrar diversas técnicas eficientes na avaliação da visão cromática humana através de métodos psicofísicos adaptativos.

Mercury and Selenium - A Review on Aspects Related to the Health of Human Populations in the Amazon

Mercury (Hg) toxicity is governed by cellular thiol compounds and its capacity to generate reactive oxygen radicals and oxidative stress. Selenium (Se) plays a key role in the prevention of the toxic effects of Hg by modulating the activity of several Se-dependent enzymes, including glutathione peroxidase (GSH-Px). In addition, dietary Se can reduce Hg toxicity by directly interacting with either Hg(II) or methylmercury (MeHg) to form inert products, such as HgSe complexes.. Although experimental and environmental data have indicated a protective role for selenium against Hg toxicity, human data are more limited and somewhat conroversial In the Amazon Region of Brazil, Hg pollution is rampant as a result of gold (Au) mining and other anthropogenic factors, leading to pervasive release of large quantities of metallic Hg⁰ into the environment. Exposure to Hg in this region is associated with direct occupational exposure in the gold mining industry, as well as consumption by in inhabitants of riverside communities of a diet rich in MeHg-contaminated fish. Human exposure to MeHg in the Amazon through the diet has been monitored by measuring Hg and MeHg in hair samples. In this paper, we review the environmental contamination of Hg in the Amazon and detail human exposures in populations of this region. We conclude with a brief synopsis on Se levels in the Amazon population and provide a brief review of data available on the interaction between Hg and Se in this region. Overall, the literature supports the notion that low environmental Se is linked to susceptibility to Hg toxicity and that Se levels could be used as a bioindicator to monitor the health of Hg exposed subjects. However, in light of the limited human data on this subject, further epidemiological studies are needed to clarify how changes in Se levels modify the toxicity of environmental Hg.

Electrophysiological evidence for impairment of contrast sensitivity in mercury vapor occupational intoxication

Contrast sensitivity (CS) was evaluated in 41 former workers from a lamp manufacturing plant who were on disability retirement due to exposure to mercury and 14 age-matched controls. The CS was measured monocularly using the sweep visual evoked potential (sVEP) paradigm at 6 spatial frequencies (0.2, 0.8, 2.0, 4.0, 15.0, and 30 cpd). Statistical difference (p<0.05) was found between the controls and the patient right and left eyes for 2.0 and 4.0 cpd. According the results in those spatial frequencies the eyes were classified in best and worst. Statistical differences were found between the controls and the best eyes for 2.0 and 4.0 cpd and for 0.8, 2.0, and 4.0 cpd for their worst eyes. No correlation was found between CS results and the time of exposure (mean=8.9 yr+/-4.1), time away from the mercury source (mean=6.0 yr+/-3.9), urinary mercury level at the time of work (mean=40.6 microg/g+/-36.3) or with the mercury level at the CS measurement time (mean=1.6 microg/g+/-1.1). We show the first evidence of a permanent impairment in CS measured objectively with the sVEP. Our data complement the previous psychophysical works reporting a diffuse impairment in the CS function showing a CS reduction in the low to middle spatial frequencies. In conclusion, non-reversible CS impairment was found in occupational exposure to mercury vapor. We suggest that CS measurement should be included in studies of the mercury effects of occupational exposure.

Visual field losses in workers exposed to mercury vapor

Visual field losses associated with mercury (Hg) exposure have only been assessed in patients exposed to methylmercury. Here we evaluate the automated visual field in 35 ex-workers (30 males; 44.20+/-5.92 years) occupationaly exposed to mercury vapor and 34 controls (21 males; 43.29+/-8.33 years). Visual fields were analyzed with the Humphrey Field Analyzer II (model 750i) using two tests: the standard automated perimetry (SAP, white-on-white) and the short wavelength automated perimetry (SWAP, blue-on-yellow) at 76 locations within a 27 degrees central visual field. Results were analyzed as the mean of the sensitivities measured at the fovea, and at five successive concentric rings, of increasing eccentricity, within the central field. Compared to controls, visual field sensitivities of the experimental group measured using SAP were lower for the fovea as well as for all five eccentricity rings (p<0.05). Sensitivities were significantly lower in the SWAP test (p<0.05) for four of the five extra-foveal eccentricity rings; they were not significant for the fovea (p=0.584) or for the 15 degrees eccentricity ring (p=0.965). These results suggest a widespread reduction of sensitivity in both visual field tests. Previous reports in the literature describe moderate to severe concentric constriction of the visual field in subjects with methylmercury intoxication measured manually with the Goldman perimeter. The present results amplify concerns regarding potential medical risks of exposure to environmental mercury sources by demonstrating significant and widespread reductions of visual sensitivity using the more reliable automated perimetry.

Scaling of neuron number and volume of the pulvinar complex in New World primates: comparisons with humans, other primates, and mammals

The lateral posterior nucleus and pulvinar (LP-pulvinar complex) are the principal thalamic nuclei associated with the elaborate development of the dorsal and ventral streams of the parietal cortex in primates. In humans, a novel site of origin for a subpopulation of pulvinar neurons has been observed, the ganglionic eminence of the telencephalon. This additional site of neuron origin has been proposed to contribute to the pulvinar's evolutionary expansion (Letinic and Rakic [2001] Nat Neurosci 4:930-936). Studies of neuron number in the LP-pulvinar complex in gibbon, chimpanzee, and gorilla compared to humans, however, did not show that the human LP-pulvinar was unexpectedly large (Armstrong [1981] Am J Phys Anthropol 55:369-383). Here we enlarge the allometric basis for comparison by determining neuron number in the LP-pulvinar complex of six New World primates (Cebus apella, Saimiri ustius, Saguinus midas niger, Alouatta caraya, Aotus azarae, and Callicebus moloch) as well as measuring LP-pulvinar volume in a further set of 24 species including additional primates, carnivores, and rodents. The volume of the LP-pulvinar complex scaled with positive allometry with respect to brain volume across all species examined. The scaling of the number of neurons in the LP-pulvinar complex was extremely similar in New World primates and anthropoid apes, with the human LP-pulvinar value close to the regression line. Comparison of the relative volumes of the LP-pulvinar in the larger sample confirmed this observation, and further demonstrated that both primates and carnivores showed a "grade shift" in its size compared to rodents, with the pulvinar comprising a greater proportion of total brain volume across the board. Diurnal, nocturnal, or crepuscular niche did not discriminate LP-pulvinar size across taxa.

Absence of binocular summation, eye dominance, and learning effects in color discrimination

We evaluated binocular summation, eye dominance, and learning in the Trivector and Ellipses procedures of the Cambridge Colour Test (CCT). Subjects (n = 36, 18-30 years old) were recruited among students and staff from the University of São Paulo. Inclusion criteria were absence of ophthalmological complaints and best-corrected Snellen VA 20/20 or better. The subjects were tested in three randomly selected eye conditions: binocular, monocular dominant eye, and nondominant eye. Results obtained in the binocular and monocular conditions did not differ statistically for thresholds measured along the protan, deutan, and tritan confusion axes (ANOVA, P > 0.05). No statistical difference was detected among discrimination ellipses obtained in binocular or monocular conditions (ANOVA, P > 0.05), suggesting absence of binocular summation or of an effect of eye dominance. Possible effects of learning were examined by comparing successive thresholds obtained in the three testing conditions. There was no evidence of improvement as a function of testing order (ANCOVA, P > 0.05). We conclude that CCT thresholds are not affected by binocularity, eye dominance, or learning. Our results differ from those found by Verriest et al. (1982) using the Farnsworth-Munsell 100 Hue test and Hovis et al. (2004) using the Farnsworth-Munsell panel D-15 test.

Estimativa da sensibilidade ao contraste espacial de luminância e discriminação de cores por meio do potencial provocado visual transiente

O potencial provocado visual (VEP) é uma resposta cortical registrável na superfície do couro cabeludo, que reflete a atividade dos neurônios de V1. é classificado, a partir da freqüência temporal de estimulação, em transiente ou de estado estacionário. Outras propriedades do estímulo parecem provocar uma atividade seletiva dos diversos grupos de neurônios existentes em V1. Desse modo, o VEP vem sendo usado para estudar a visão humana acromática e cromática. Diversos trabalhos usaram o VEP para estimar a sensibilidade ao contraste de luminância no domínio das freqüências espaciais. Mais recentemente, há estudos que empregaram o VEP para medir os limiares de discriminação de cores. O VEP transiente pode complementar as medidas psicofísicas de sensibilidade ao contraste espacial de luminância e de discriminação cromática, e constitui um método não invasivo para estudar a visão de indivíduos com dificuldades de realizar testes psicofísicos.

Espaço de cores

O artigo apresenta definições para os termos espaço de cores e sistemas de cores; classifica, de acordo com David Brainard (2003), os sistemas de cores em dois grupos: aparência de cores e diferenças de cores. Dentre os diversos sistemas de cores existentes, o artigo descreve dois deles: o sistema de cores Munsell &– um dos mais utilizados entre os sistemas de aparência de cores &– e a descrição do sistema de cores CIE 1931 &– um dos mais utilizados dentre os sistemas de diferença de cores. Faz-se uma retrospectiva histórica da busca por espaços de cores que representem a percepção de cores humana assim como as diversas reconstruções de espaços de cores por métodos eletrofisiológicos ou psicofísicos. Muitas dessas reconstruções utilizam a escala multidimensional (mds). O artigo também introduz a possibilidade da reconstrução dos espaços de cores de pacientes com discromatopsia adquirida como uma distorção do espaço de indivíduos tricromatas normais.

Peripheral variability and central constancy in mammalian visual system evolution

Neural systems are necessarily the adaptive products of natural selection, but a neural system, dedicated to any particular function in a complex brain, may be composed of components that covary with functionally unrelated systems, owing to constraints beyond immediate functional requirements. Some studies support a modular or mosaic organization of the brain, whereas others emphasize coordination and covariation. To contrast these views, we have analysed the retina, striate cortex (V1) and extrastriate cortex (V2, V3, MT, etc.) in 30 mammals, examining the area of the neocortex and individual neocortical areas and the relative numbers of rods and cones. Controlling for brain size and species relatedness, the sizes of visual cortical areas (striate, extrastriate) within the brains of nocturnal and diurnal mammals are not statistically different from one another. The relative sizes of all cortical areas, visual, somatosensory and auditory, are best predicted by the total size of the neocortex. In the sensory periphery, the retina is clearly specialized for niche. New data on rod and cone numbers in various New World primates confirm that rod and cone complements of the retina vary substantially between nocturnal and diurnal species. Although peripheral specializations or receptor surfaces may be highly susceptible to niche-specific selection pressures, the areal divisions of the cerebral cortex are considerably more conservative.