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- Color improves "visual" acuity via sound. [JOURNAL ARTICLE]
- Front Neurosci 2014.:358.
Visual-to-auditory sensory substitution devices (SSDs) convey visual information via sound, with the primary goal of making visual information accessible to blind and visually impaired individuals. We developed the EyeMusic SSD, which transforms shape, location, and color information into musical notes. We tested the "visual" acuity of 23 individuals (13 blind and 10 blindfolded sighted) on the Snellen tumbling-E test, with the EyeMusic. Participants were asked to determine the orientation of the letter "E." The test was repeated twice: in one test, the letter "E" was drawn with a single color (white), and in the other test, with two colors (red and white). In the latter case, the vertical line in the letter, when upright, was drawn in red, with the three horizontal lines drawn in white. We found no significant differences in performance between the blind and the sighted groups. We found a significant effect of the added color on the "visual" acuity. The highest acuity participants reached in the monochromatic test was 20/800, whereas with the added color, acuity doubled to 20/400. We conclude that color improves "visual" acuity via sound.
- Efficient hybrid white organic light-emitting diodes with extremely long lifetime: the effect of n-type interlayer. [Journal Article]
- Sci Rep 2014.:7198.
The effect of n-type interlayer in hybrid white organic light-emitting diodes (WOLEDs) has been systematically investigated by using various n-type materials. A new finding, that the triplet energy rather than electron mobility or hole-blocking ability of interlayer plays a more positive role in the performance of hybrid WOLEDs, is demonstrated. Based on the new finding, a more efficient n-type interlayer bis[2-(2-hydroxyphenyl)-pyridine] beryllium has been employed to realize a high-performance hybrid WOLED. The resulting device (without n-doping technology) exhibits low voltages (i.e., 2.8 V for 1 cd/m(2), 3.9 V for 100 cd/m(2)) and low efficiency roll-off (i.e., 11.5 cd/A at 100 cd/m(2) and 11.2 cd/A at 1000 cd/m(2)). At the display-relevant luminance of 100 cd/m(2), a total power efficiency of 16.0 lm/W, a color rendering index of 73 and an extremely long lifetime of 12596265 h are obtained. Such superior results not only comprehensively indicate that the n-type materials are effective interlayers to develop high-performance hybrid WOLEDs but also demonstrate a significant step towards real commercialization in WOLEDs.
- Wall lizards display conspicuous signals to conspecifics and reduce detection by avian predators. [JOURNAL ARTICLE]
- Behav Ecol 2014 11; 25(6):1325-1337.
Visual signals are often under conflicting selection to be hidden from predators while being conspicuous to mates and rivals. Here, we investigated whether 3 different island populations of Aegean wall lizards (Podarcis erhardii) with variable coloration among diverse island habitats exhibit simultaneous camouflage and sexual signals. We examined whether signals appear better tuned to conspecific vision as opposed to that of avian predators, and whether background-matching camouflage and sexual signals are partitioned to specific body regions. This could facilitate both covert sexual signaling and camouflage according to the viewing perspectives of predators and conspecifics. We found that lizards typically appeared twice as conspicuous to conspecifics than to avian predators against the same visual background, largely due to lizards' enhanced sensitivity to ultraviolet, suggesting that P. erhardii signals are tuned to conspecific vision to reduce detection by predators. Males were more conspicuous than females to both predators and conspecifics. In 2 populations, male backs were relatively more camouflaged to predators compared to signaling flanks, whereas in females, exposed and concealed surfaces were camouflaged to predators and generally did not differ in background matching. These findings indicate that lizard coloration evolves under the competing demands of natural and sexual selection to promote signals that are visible to conspecifics while being less perceptible to avian predators. They also elucidate how interactions between natural and sexual selection influence signal detectability and partitioning to different body regions, highlighting the importance of considering receiver vision, viewing perspectives, and signaling environments in studies of signal evolution.
- Chromatic and Achromatic Spatial Resolution of Local Field Potentials in Awake Cortex. [JOURNAL ARTICLE]
- Cereb Cortex 2014 Nov 21.
Local field potentials (LFPs) have become an important measure of neuronal population activity in the brain and could provide robust signals to guide the implant of visual cortical prosthesis in the future. However, it remains unclear whether LFPs can detect weak cortical responses (e.g., cortical responses to equiluminant color) and whether they have enough visual spatial resolution to distinguish different chromatic and achromatic stimulus patterns. By recording from awake behaving macaques in primary visual cortex, here we demonstrate that LFPs respond robustly to pure chromatic stimuli and exhibit ∼2.5 times lower spatial resolution for chromatic than achromatic stimulus patterns, a value that resembles the ratio of achromatic/chromatic resolution measured with psychophysical experiments in humans. We also show that, although the spatial resolution of LFP decays with visual eccentricity as is also the case for single neurons, LFPs have higher spatial resolution and show weaker response suppression to low spatial frequencies than spiking multiunit activity. These results indicate that LFP recordings are an excellent approach to measure spatial resolution from local populations of neurons in visual cortex including those responsive to color.
- Compensation for red-green contrast loss in anomalous trichromats. [Journal Article]
- J Vis 2014; 14(13)
For anomalous trichromats, threshold contrasts for color differences captured by the L and M cones and their anomalous analogs are much higher than for normal trichromats. The greater spectral overlap of the cone sensitivities reduces chromatic contrast both at and above threshold. But above threshold, adaptively nonlinear processing might compensate for the chromatically impoverished photoreceptor inputs. Ratios of sensitivity for threshold variations and for color appearance along the two cardinal axes of MacLeod-Boynton chromaticity space were calculated for three groups: normals (N = 15), deuteranomals (N = 9), and protanomals (N = 5). Using a four-alternative forced choice (4AFC) task, threshold sensitivity was measured in four color-directions along the two cardinal axes. For the same participants, we reconstructed perceptual color spaces for the positions of 25 hues using multidimensional scaling (MDS). From the reconstructed color spaces we extracted "color difference ratios," defined as ratios for the size of perceived color differences along the L/(L + M) axis relative to those along the S/(L + M) axis, analogous to "sensitivity ratios" extracted from the 4AFC task. In the 4AFC task, sensitivity ratios were 38% of normal for deuteranomals and 19% of normal for protanomals. Yet, in the MDS results, color difference ratios were 86% of normal for deuteranomals and 67% of normal for protanomals. Thus, the contraction along the L/(L + M) axis shown in the perceptual color spaces of anomalous trichromats is far smaller than predicted by their reduced sensitivity, suggesting that an adaptive adjustment of postreceptoral gain may magnify the cone signals of anomalous trichromats to exploit the range of available postreceptoral neural signals.
- Vision-Related Quality-of-Life Assessment Using NEI VFQ-25 in Patients After Boston Keratoprosthesis Implantation. [JOURNAL ARTICLE]
- Cornea 2014 Nov 19.
The aim of this study was to determine the impact of Boston keratoprosthesis (KPro) implantation on patient-reported visual function using the National Eye Institute Visual Function Questionnaire 25 (NEI VFQ-25).This is a prospective study of patients undergoing implantation of Boston KPro. The NEI VFQ-25 was used to assess vision-related quality of life preoperatively and postoperatively at 3 and 6 months and yearly thereafter. Baseline scores were compared with postoperative scores using paired t test. Stratified analysis was performed to compare results by visual acuity of the contralateral eye.Twenty-four patients were included. Mean baseline NEI VFQ-25 overall score was 44.6. At the first follow-up time point, mean overall score was 70.0, representing a statistically significant change from baseline (P < 0.001). Breakdown of subcategories within VFQ-25 showed significant improvement in general vision, near and distance activities, social functioning, mental health, role difficulties, dependency, color vision, and peripheral vision (P < 0.05). This improvement was also observed when comparing baseline scores with postoperative scores at average follow-up of 16 months. Although a greater change in scores was observed in patients who had poor vision in the contralateral eye, patients with vision better than 20/200 in the nonsurgical eye showed statistically significant improvement in overall scores and subscale scores compared with baseline.The quality of life of patients who underwent KPro significantly improved postoperatively compared with their preoperative status. These results did not change when stratifying by visual acuity of the contralateral eye.
- Alouatta trichromatic color vision: cone spectra and physiological responses studied with microspectrophotometry and single unit retinal electrophysiology. [Journal Article]
- PLoS One 2014; 9(11):e113321.
The howler monkeys (Alouatta sp.) are the only New World primates to exhibit routine trichromacy. Both males and females have three cone photopigments. However, in contrast to Old World monkeys, Alouatta has a locus control region upstream of each opsin gene on the X-chromosome and this might influence the retinal organization underlying its color vision. Post-mortem microspectrophotometry (MSP) was performed on the retinae of two male Alouatta to obtain rod and cone spectral sensitivities. The MSP data were consistent with only a single opsin being expressed in each cone and electrophysiological data were consistent with this primate expressing full trichromacy. To study the physiological organization of the retina underlying Alouatta trichromacy, we recorded from retinal ganglion cells of the same animals used for MSP measurements with a variety of achromatic and chromatic stimulus protocols. We found MC cells and PC cells in the Alouatta retina with similar properties to those previously found in the retina of other trichromatic primates. MC cells showed strong phasic responses to luminance changes and little response to chromatic pulses. PC cells showed strong tonic response to chromatic changes and small tonic response to luminance changes. Responses to other stimulus protocols (flicker photometry; changing the relative phase of red and green modulated lights; temporal modulation transfer functions) were also similar to those recorded in other trichromatic primates. MC cells also showed a pronounced frequency double response to chromatic modulation, and with luminance modulation response saturation accompanied by a phase advance between 10-20 Hz, characteristic of a contrast gain mechanism. This indicates a very similar retinal organization to Old-World monkeys. Cone-specific opsin expression in the presence of a locus control region for each opsin may call into question the hypothesis that this region exclusively controls opsin expression.
- Ophthalmological features of Parkinson disease. [Journal Article]
- Med Sci Monit 2014.:2243-9.
Background The aim of this study was to determine the type and frequency of ophthalmologic changes occurring in patients with Parkinson disease (PD). Material and Methods One hundred consecutive patients (196 eyes) with idiopathic PD and a control group consisting of 100 healthy patients (196 eyes) matched for age and sex underwent a complete ophthalmological examination of both eyes, including assessment of patient medical history, dry eye questionare, and visual hallucinations questionnaire, distance and near best corrected visual acuity (DBCVA, NBCVA), color vision, distance photopic contrast sensitivity, near point of convergence, slit lamp examination of the eye anterior segment, tear film osmolarity and breakup time, aqueous tear production, and intraocular pressure, as well as fundus examination and evaluation of the perimacular retinal thickness (RT) and peripapillary retinal nerve fiber layer (RNFL) thickness. Results In the eyes of PD patients DBCVA, NBCVA, contrast sensitivity, and color discrimination were significantly reduced. We also detected increased frequency of convergence insufficiency, seborrhoic blepharitis, meibomian gland disease (MGD), dry eye syndrome, nuclear and posterior subcapsular cataract, and glaucoma (p<0.05). However, intraocular pressure (IOP) was significantly lower in the PD group compared to controls. The frequency of visual hallucinations, age-related macular degeneration (ARMD), and other ophthalmological diseases, as well as RT and RNFL thickness, did not significantly differ between investigated groups. Conclusions Clinicians need to be aware of the association between PD and ophthalmological changes. Restoration of good-quality vision has a great impact on PD patients' quality of life, reduction of costs of treatment and care, and rehabilitation.
- High-speed odor transduction and pulse tracking by insect olfactory receptor neurons. [JOURNAL ARTICLE]
- Proc Natl Acad Sci U S A 2014 Nov 10.
Sensory systems encode both the static quality of a stimulus (e.g., color or shape) and its kinetics (e.g., speed and direction). The limits with which stimulus kinetics can be resolved are well understood in vision, audition, and somatosensation. However, the maximum temporal resolution of olfactory systems has not been accurately determined. Here, we probe the limits of temporal resolution in insect olfaction by delivering high frequency odor pulses and measuring sensory responses in the antennae. We show that transduction times and pulse tracking capabilities of olfactory receptor neurons are faster than previously reported. Once an odorant arrives at the boundary layer of the antenna, odor transduction can occur within less than 2 ms and fluctuating odor stimuli can be resolved at frequencies more than 100 Hz. Thus, insect olfactory receptor neurons can track stimuli of very short duration, as occur when their antennae encounter narrow filaments in an odor plume. These results provide a new upper bound to the kinetics of odor tracking in insect olfactory receptor neurons and to the latency of initial transduction events in olfaction.
- Bilateral subinternal limiting membrane hemorrhage in benzene toxicity. [Journal Article]
- Retin Cases Brief Rep 2014; 8(4):276-8.
To report the clinical and spectral domain optical coherence tomography findings in a patient with bilateral central vision loss and a history of exposure to polyamides.The clinical presentation of the patient was documented with color fundus photographs and spectral domain optical coherence tomography. The patient was a 20-year-old male factory worker with no medical history who was initially admitted for workup of hematologic malignancy due to petechiae and fevers.Optical coherence tomography revealed bilateral hemorrhages in the subinternal limiting membrane space resembling Valsalva retinopathy. Complete blood count revealed pancytopenia and marked thrombocytopenia.Heavy exposure to benzene, a byproduct of the polyamide-curing process, is known to cause aplastic anemia. Accompanying thrombocytopenia may increase the risk of spontaneous subinternal limiting membrane hemorrhage.