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- Homozygous missense variant in the human CNGA3 channel causes cone-rod dystrophy. [JOURNAL ARTICLE]
- Eur J Hum Genet 2014 Jul 23.
We assessed a large consanguineous Pakistani family (PKAB157) segregating early onset low vision problems. Funduscopic and electroretinographic evaluation of affected individuals revealed juvenile cone-rod dystrophy (CRD) with maculopathy. Other clinical symptoms included loss of color discrimination, photophobia and nystagmus. Whole-exome sequencing, segregation and haplotype analyses demonstrated that a transition variant (c.955T>C; p.(Cys319Arg)) in CNGA3 co-segregated with the CRD phenotype in family PKAB157. The ability of CNGA3 channel to influx calcium in response to agonist, when expressed either alone or together with the wild-type CNGB3 subunit in HEK293 cells, was completely abolished due to p.Cys319Arg variant. Western blotting and immunolocalization studies suggest that a decreased channel density in the HEK293 cell membrane due to impaired folding and/or trafficking of the CNGA3 protein is the main pathogenic effect of the p.Cys319Arg variant. Mutant alleles of the human cone photoreceptor cyclic nucleotide-gated channel (CNGA3) are frequently associated with achromatopsia. In rare cases, variants in CNGA3 are also associated with cone dystrophy, Leber's congenital amaurosis and oligo cone trichromacy. The identification of predicted p.(Cys319Arg) missense variant in CNGA3 expands the repertoire of the known genetic causes of CRD and phenotypic spectrum of CNGA3 alleles.European Journal of Human Genetics advance online publication, 23 July 2014; doi:10.1038/ejhg.2014.136.
- Quantification of Pizza Baking Properties of Different Cheeses, and Their Correlation with Cheese Functionality. [JOURNAL ARTICLE]
- J Food Sci 2014 Jul 21.
The aim of this study is to quantify the pizza baking properties and performance of different cheeses, including the browning and blistering, and to investigate the correlation to cheese properties (rheology, free oil, transition temperature, and water activity). The color, and color uniformity, of different cheeses (Mozzarella, Cheddar, Colby, Edam, Emmental, Gruyere, and Provolone) were quantified, using a machine vision system and image analysis techniques. The correlations between cheese appearance and attributes were also evaluated, to find that cheese properties including elasticity, free oil, and transition temperature influence the color uniformity of cheeses.
- Identifying Functional Connections of the Inner Photoreceptors in Drosophila using Tango-Trace. [JOURNAL ARTICLE]
- Neuron 2014 Jul 17.
In Drosophila, the four inner photoreceptor neurons exhibit overlapping but distinct spectral sensitivities and mediate behaviors that reflect spectral preference. We developed a genetic strategy, Tango-Trace, that has permitted the identification of the connections of the four chromatic photoreceptors. Each of the four stochastically distributed chromatic photoreceptor subtypes make distinct connections in the medulla with four different TmY cells. Moreover, each class of TmY cells forms a retinotopic map in both the medulla and the lobula complex, generating four overlapping topographic maps that could carry different color information. Thus, the four inner photoreceptors transmit spectral information through distinct channels that may converge in both the medulla and lobula complex. These projections could provide an anatomic basis for color vision and may relay information about color to motion sensitive areas. Moreover, the Tango-Trace strategy we used may be applied more generally to identify neural circuits in the fly brain.
- Color-detection thresholds in rhesus macaque monkeys and humans. [Journal Article]
- J Vis 2014; 14(8)
MACAQUE MONKEYS ARE A MODEL OF HUMAN COLOR VISION TO FACILITATE LINKING PHYSIOLOGY IN MONKEYS WITH PSYCHOPHYSICS IN HUMANS, WE DIRECTLY COMPARED COLOR-DETECTION THRESHOLDS IN HUMANS AND RHESUS MONKEYS: COLORS WERE DEFINED BY AN EQUILUMINANT PLANE OF CONE-OPPONENT COLOR SPACE ALL SUBJECTS WERE TESTED ON AN IDENTICAL APPARATUS WITH A FOUR-ALTERNATIVE FORCED-CHOICE TASK TARGETS WERE 2° SQUARE, CENTERED 2° FROM FIXATION, EMBEDDED IN LUMINANCE NOISE ACROSS ALL SUBJECTS, THE CHANGE IN DETECTION THRESHOLDS FROM INITIAL TESTING TO PLATEAU PERFORMANCE "LEARNING" WAS SIMILAR FOR +L - M RED COLORS AND +M - L BLUISH-GREEN COLORS BUT THE EXTENT OF LEARNING WAS HIGHER FOR +S LAVENDER THAN FOR -S YELLOW-LIME; MOREOVER, AT PLATEAU PERFORMANCE, THE CONE CONTRAST AT THE DETECTION THRESHOLD WAS HIGHER FOR +S THAN FOR -S THESE ASYMMETRIES MAY REFLECT DIFFERENCES IN RETINAL CIRCUITRY FOR S-ON AND S-OFF AT PLATEAU PERFORMANCE, THE TWO SPECIES ALSO HAD SIMILAR DETECTION THRESHOLDS FOR ALL COLORS, ALTHOUGH MONKEYS HAD SHORTER REACTION TIMES THAN HUMANS AND SLIGHTLY LOWER THRESHOLDS FOR COLORS THAT MODULATED L/M CONES WE DISCUSS WHETHER THESE OBSERVATIONS, TOGETHER WITH PREVIOUS WORK SHOWING THAT MONKEYS HAVE LOWER SPATIAL ACUITY THAN HUMANS, COULD BE ACCOUNTED FOR BY SELECTIVE PRESSURES DRIVING HIGHER CHROMATIC SENSITIVITY AT THE COST OF SPATIAL ACUITY AMONGST MONKEYS, SPECIFICALLY FOR THE MORE RECENTLY EVOLVED L - M MECHANISM:
- Properties of artificial networks evolved to contend with natural spectra. [JOURNAL ARTICLE]
- Proc Natl Acad Sci U S A 2014 Jul 14.
Understanding why spectra that are physically the same appear different in different contexts (color contrast), whereas spectra that are physically different appear similar (color constancy) presents a major challenge in vision research. Here, we show that the responses of biologically inspired neural networks evolved on the basis of accumulated experience with spectral stimuli automatically generate contrast and constancy. The results imply that these phenomena are signatures of a strategy that biological vision uses to circumvent the inverse optics problem as it pertains to light spectra, and that double-opponent neurons in early-level vision evolve to serve this purpose. This strategy provides a way of understanding the peculiar relationship between the objective world and subjective color experience, as well as rationalizing the relevant visual circuitry without invoking feature detection or image representation.
- The role of Magnetic Resonance Imaging and Visual Evoked Potential in management of optic neuritis. [Journal Article]
- Pan Afr Med J 2014.:54.
To report our experience in management of patients with optic neuritis. The effects of brain magnetic resonance imaging and visual evoked potential on management were investigated.This is a four years clinical trial that included patients presenting with first attack of optic neuritis older than 16 years with visual acuity of less than 6/60 and presentation within first week of illness. Brain magnetic resonance imaging and visual evoked potentials were done for all patients. Patients were classified into three groups. First group received placebo, second received oral steroids and third received intravenous and oral steroids. Primary outcome measure was improvement in visual acuity.A total number of 150 patients were enrolled in the study. Ocular pain was seen 127 patients Relative afferent pupillary defect in 142 patients and color vision impairment in 131 patients. Abnormal MRI findings were seen in 84 patients. Pattern reversal VEP was abnormal in all patients. Using oral or intravenous steroid resulted in faster recovery but did not affect the final visual outcome. Recurrence rate was higher in patients with multiple MRI lesions and diminished VEP amplitude. Using intravenous steroids decreased recurrence rate in patients with three and more MRI lesions and non recordable VEP response.MRI and pattern reversal VEP are recommended to be done in all patients presenting with optic neuritis. We advise to give intravenous methyl prednisolone in patients with multiple MRI white matter lesions and non recordable VEP at presentation.
- Why do green rods of frog and toad retinas look green? [JOURNAL ARTICLE]
- J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2014 Jul 12.
Amphibian "green" rods express a blue-sensitive cone visual pigment, and should look yellow. However, when observing them axially under microscope one sees them as green. We used single-cell microspectrophotometry (MSP) to reveal the basis of the perceived color of these photoreceptors. Conventional side-on MSP recording of the proximal cell segments reveals no selective long-wave absorbing pigment explaining the green color. End-on MSP recording shows, in addition to the green rod visual pigment, an extra 2- to 4-fold attenuation being almost flat throughout the visible spectrum. This attenuation is absent in red (rhodopsin) rods, and vanishes in green rods when the retina is bathed in high-refractive media, and at wide illumination aperture. The same treatments change the color from green to yellow. It seems that the non-visual pigment attenuation is a result of slender green rod myoids operating as non-selective light guides. We hypothesize that narrow myoids, combined with photomechanical movements of melanin granules, allow a wide range of sensitivity regulation supporting the operation of green rods as blue receptors at mesopic-to low-photopic illumination levels. End-on transmittance spectrum of green rods looks similar to the reflectance spectrum of khaki military uniforms. So their greenness is the combined result of optics and human color vision.
- A Multiscale Optimization Approach to Detect Exudates in the Macula. [JOURNAL ARTICLE]
- IEEE J Biomed Health Inform 2014 Jul; 18(4):1328-1336.
Pathologies that occur on or near the fovea, such as clinically significant macular edema (CSME), represent high risk for vision loss. The presence of exudates, lipid residues of serous leakage from damaged capillaries, has been associated with CSME, in particular if they are located one optic disc-diameter away from the fovea. In this paper, we present an automatic system to detect exudates in the macula. Our approach uses optimal thresholding of instantaneous amplitude (IA) components that are extracted from multiple frequency scales to generate candidate exudate regions. For each candidate region, we extract color, shape, and texture features that are used for classification. Classification is performed using partial least squares (PLS). We tested the performance of the system on two different databases of 652 and 400 images. The system achieved an area under the receiver operator characteristic curve (AUC) of 0.96 for the combination of both databases and an AUC of 0.97 for each of them when they were evaluated independently.
- A Food Recognition System for Diabetic Patients Based on an Optimized Bag-of-Features Model. [JOURNAL ARTICLE]
- IEEE J Biomed Health Inform 2014 Jul; 18(4):1261-1271.
Computer vision-based food recognition could be used to estimate a meal's carbohydrate content for diabetic patients. This study proposes a methodology for automatic food recognition, based on the bag-of-features (BoF) model. An extensive technical investigation was conducted for the identification and optimization of the best performing components involved in the BoF architecture, as well as the estimation of the corresponding parameters. For the design and evaluation of the prototype system, a visual dataset with nearly 5000 food images was created and organized into 11 classes. The optimized system computes dense local features, using the scale-invariant feature transform on the HSV color space, builds a visual dictionary of 10000 visual words by using the hierarchical k-means clustering and finally classifies the food images with a linear support vector machine classifier. The system achieved classification accuracy of the order of 78%, thus proving the feasibility of the proposed approach in a very challenging image dataset.