Download the Free Unbound MEDLINE PubMed App to your smartphone or tablet.
Available for iPhone, iPad, iPod touch, and Android.
- A new method to measure higher visual functions in an immersive environment. [JOURNAL ARTICLE]
- Biomed Eng Online 2014 Jul 28; 13(1):104.
Higher visual functions can be defined as cognitive processes responsible for object recognition, color and shape perception, and motion detection. People with impaired higher visual functions after unilateral brain lesion are often tested with paper pencil tests, but such tests do not assess the degree of interaction between the healthy brain hemisphere and the impaired one. Hence, visual functions are not tested separately in the contralesional and ipsilesional visual hemifields.A new measurement setup, that involves real-time comparisons of shape and size of objects, orientation of lines, speed and direction of moving patterns, in the right or left visual hemifield, has been developed. The setup was implemented in an immersive environment like a hemisphere to take into account the effects of peripheral and central vision, and eventual visual field losses. Due to the non-flat screen of the hemisphere, a distortion algorithm was needed to adapt the projected images to the surface. Several approaches were studied and, based on a comparison between projected images and original ones, the best one was used for the implementation of the test. Fifty-seven healthy volunteers were then tested in a pilot study. A Satisfaction Questionnaire was used to assess the usability of the new measurement setup.The results of the distortion algorithm showed a structural similarity between the warped images and the original ones higher than 97%. The results of the pilot study showed an accuracy in comparing images in the two visual hemifields of 0.18 visual degrees and 0.19 visual degrees for size and shape discrimination, respectively, 2.56[degree sign] for line orientation, 0.33 visual degrees/s for speed perception and 7.41[degree sign] for recognition of motion direction. The outcome of the Satisfaction Questionnaire showed a high acceptance of the battery by the participants.A new method to measure higher visual functions in an immersive environment was presented. The study focused on the usability of the developed battery rather than the performance at the visual tasks. A battery of five subtasks to study the perception of size, shape, orientation, speed and motion direction was developed. The test setup is now ready to be tested in neurological patients.
- Objective Analyses of Tessellated Fundi and Significant Correlation between Degree of Tessellation and Choroidal Thickness in Healthy Eyes. [Journal Article]
- PLoS One 2014; 9(7):e103586.
A tessellated fundus is a common characteristic of myopic eyes and is an important clinical marker for the development of retinochoroidal changes. However, the exact cause and significance of tessellated fundi have not been definitively determined. We determined the degree of tessellation in fundi objectively in normal, non-pathological myopic eyes, and correlated the degree of tessellation and the choroidal thickness (CT) and axial length (AL). This was a prospective observational cross sectional study. The eyes were classified subjectively into three groups based on the degree of tessellation observed ophthalmoscopically. Digital color fundus photographs were assessed for the degree of tessellation by ImageJ, an image processing program. Three tessellated fundus indices (TFIs) were calculated and were compared to the three subjectively-determined groups. The subfoveal and nasal CTs were measured in the optical coherence tomographic images. The correlations between the TFIs and the CT were calculated. Additionally, the correlation between the TFIs and the AL was calculated. One hundred right eyes of 100 healthy volunteers (mean age 25.8±3.9 years) were studied. Ophthalmoscopically, 57 eyes were placed in the non-tessellated group, 27 eyes into the weakly tessellated group, and 16 eyes into the strongly tessellated group. There was a significant correlation between the subjective classifications and the TFI values (P<0.05, Kruskal-Wallis test). All of the TFIs were significantly associated with the subfoveal and nasal CT (R = -0.20 to -0.24, P<0.05). The TFIs were not significantly correlated with the ALs. In conclusion, the significant correlation between the subjective and objective classifications of the degree of tessellation indicates that TFIs can be used to classify the degree of tessellation. The results indicate that the differences in the CT account for the degree of tessellation.
- Possible functions of contextual modulations and receptive field nonlinearities: pop-out and texture segmentation. [JOURNAL ARTICLE]
- Vision Res 2014 Jul 23.
When analyzing a visual image, the brain has to achieve several goals quickly. One crucial goal is to rapidly detect parts of the visual scene that might be behaviorally relevant, while another one is to segment the image into objects, to enable an internal representation of the world. Both of these processes can be driven by local variations in any of several image attributes such as luminance, color, and texture. Here, focusing on texture defined by local orientation, we propose that the two processes are mediated by separate mechanisms that function in parallel. More specifically, differences in orientation can cause an object to "pop out" and attract visual attention, if its orientation differs from that of the surrounding objects. Differences in orientation can also signal a boundary between objects and therefore provide useful information for image segmentation. We propose that contextual response modulations in primary visual cortex (V1) are responsible for orientation pop-out, while a different kind of receptive field nonlinearity in secondary visual cortex (V2) is responsible for orientation-based texture segmentation. We review a recent experiment that led us to put forward this hypothesis along with other research literature relevant to this notion.
- Cognitive control predicted by color vision, and vice versa. [JOURNAL ARTICLE]
- Neuropsychologia 2014 Jul 21.
One of the most important functions of cognitive control is to continuously adapt cognitive processes to changing and often conflicting demands of the environment.Dopamine (DA) has been suggested to play a key role in the signaling and resolution of such response conflict.Given that DA is found in high concentration in the retina, color vision discrimination has been suggested as an index of DA functioning and in particular blue-yellow color vision impairment (CVI) has been used to indicate a central hypodopaminergic state. We used color discrimination (indexed by the total color distance score; TCDS) to predict individual differences in the cognitive control of response conflict, as reflected by conflict-resolution efficiency in an auditory Simon task. As expected, participants showing better color discrimination were more efficient in resolving response conflict. Interestingly, participants showing a blue-yellow CVI were associated with less efficiency in handling response conflict. Our findings indicate that color vision discrimination might represent a promising predictor of cognitive controlability in healthy individuals.
- Toxic effects of chronic mercury exposure on the retinal nerve fiber layer and macular and choroidal thickness in industrial mercury battery workers. [Journal Article]
- Med Sci Monit 2014.:1284-90.
Background The aim of this study was to evaluate the toxic effects of mercury on retinal nerve fiber layer thickness (RNFLT), macular thickness (MT), and choroidal thickness (CT) by using spectral-domain optical coherence tomography (SD-OCT) in battery industry workers who had been chronically exposed to mercury. Material and Methods Battery factory workers (n=31) and healthy non-factory employee controls (n=15) participated in the study. Participants were divided into 3 groups: Group 1 (n=15) was factory workers who had worked for more than 5 years in a mercury battery factory; Group 2 (n=16) was factory worker who had worked for less than 5 years in a mercury battery factory; and Group 3 (n=15) was healthy non-employees. Systemic symptoms were recorded. Ophthalmic examination included best-corrected visual acuity test, color vision test, full ophthalmologic examination, and SD-OCT of the RNLF, macula, and choroid. To determine mercury exposure, venous blood samples were collected and mercury levels were assessed. Results In our study group the most common systemic symptoms were insomnia (67.7%) and fatigue (67.7%). There were no significant differences between Group 1 and Group 2, but there were significant differences between Group 3 and both Group 1 and Group 2 in best-corrected visual acuity values (1=2<3), color vision scores, blood mercury levels, and duration (mean ±SD, range) of mercury exposure(1>2>3). OCT values of RNFLTs, MTs, and CTs of all 3 groups were statistically different from each another (1<2<3). Conclusions SD-OCT can be useful for evaluating the toxic effects of chronic exposure to mercury.
- 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: