- Central Brain Circuitry for Color-Vision-Modulated Behaviors. [Review]
- CBCurr Biol 2016 Oct 24; 26(20):R981-R988
- Color is famous for not existing in the external world: our brains create the perception of color from the spatial and temporal patterns of the wavelength and intensity of light. For an intangible qu...
Color is famous for not existing in the external world: our brains create the perception of color from the spatial and temporal patterns of the wavelength and intensity of light. For an intangible quality, we have detailed knowledge of its origins and consequences. Much is known about the organization and evolution of the first phases of color processing, the filtering of light in the eye and processing in the retina, and about the final phases, the roles of color in behavior and natural selection. To understand how color processing in the central brain has evolved, we need well-defined pathways or circuitry where we can gauge how color contributes to the computations involved in specific behaviors. Examples of such pathways or circuitry that are dedicated to processing color cues are rare, despite the separation of color and luminance pathways early in the visual system of many species, and despite the traditional definition of color as being independent of luminance. This minireview presents examples in which color vision contributes to behaviors dominated by other visual modalities, examples that are not part of the canon of color vision circuitry. The pathways and circuitry process a range of chromatic properties of objects and their illumination, and are taken from a variety of species. By considering how color processing complements luminance processing, rather than being independent of it, we gain an additional way to account for the diversity of color coding in the central brain, its consequences for specific behaviors and ultimately the evolution of color vision.
- Color Vision and Performance on Color-Coded Cockpit Displays. [Journal Article]
- AMAerosp Med Hum Perform 2016; 87(11):921-927
- CONCLUSIONS: Although lower CCT scores are clearly associated with lower performance in color related tasks, the magnitude of the performance loss was relatively small and there were multiple examples of high-performing CVD individuals who had higher operational scores than low-performing CVN individuals. Gaska JP, Wright ST, Winterbottom MD, Hadley SC. Color vision and performance on color-coded cockpit displays. Aerosp Med Hum Perform. 2016; 87(11):921-927.
- Contrast dependence of saccadic blanking and landmark effects. [Journal Article]
- VRVision Res 2016 Oct 20
- Two phenomena have been reported to affect the perceived displacement of a visual target during saccadic eye movements: the blanking effect and landmark effect. In the blanking effect, temporarily bl...
Two phenomena have been reported to affect the perceived displacement of a visual target during saccadic eye movements: the blanking effect and landmark effect. In the blanking effect, temporarily blanking the target after a saccade improves displacement judgments. In the landmark effect, illusory target displacement occurs when a continuously presented landmark is displaced during a saccade, and the target is temporarily blanked after the saccade without displacement. We show that the strengths of the blanking and landmark effects vary with stimulus contrast. In the blanking effect, target displacement detection rate increased with luminance contrast of the target. In the landmark effect, illusory target displacement decreased with luminance contrast of the target. Moreover, the landmark effect was found even for stimuli without luminance contrast (equiluminant color stimuli), while the blanking effect disappeared. These results can be attributed to a reduction in sensitivity of target displacement by a reduction of luminance contrast, which suggests that changes in luminance, or transient signals, play a critical role in visual stability across saccades.
- Electrophysiological correlates of visual binding errors after bilateral parietal damage. [Journal Article]
- NNeuroscience 2016 Nov 19; 337:98-106
- Illusory conjunctions (e.g. the confusion between the shape of one stimulus with the color of another stimulus) are the most dramatic expression of binding failures in vision. Under brief exposure or...
Illusory conjunctions (e.g. the confusion between the shape of one stimulus with the color of another stimulus) are the most dramatic expression of binding failures in vision. Under brief exposure or when attention is diverted illusory conjunctions may be observed in healthy participants, but they only represent a real-life problem for patients with parietal damage. However, it is unclear whether such failures reflect the impairment of early or late stages of visual processing. Here, we examined the time-course of visual processing using evoked potential measures in a patient with bilateral damage to the posterior parietal cortex presenting prominent binding failures. The patient was asked to identify colored letters that were briefly flashed to the left or right hemifield. When only one item was presented she adequately identified color or shape of left and right letters. In contrast, when presentation was bilateral she either identified the correct right shape-color combination and missed the item in the left hemifield (extinction) or combined incorrectly the right shape with the left color (illusory conjunction). Evoked potential analyses revealed a specific electrophysiological signature of illusory conjunctions, starting ∼105ms after stimulus onset over the right frontal cortex. These findings indicate that binding errors reflect failures of early stages of attentional filtering relying on the integrity of the posterior parietal cortex.
- DETAILED CLINICAL PHENOTYPING OF OXALATE MACULOPATHY IN PRIMARY HYPEROXALURIA TYPE 1 AND REVIEW OF THE LITERATURE. [Journal Article]
- RRetina 2016; 36(11):2227-2235
- CONCLUSIONS: Retinopathy in PH Type 1 shows considerable interindividual variation. No correlation between genotype and retinal phenotype was detected. Oxalate crystals at the level of the retinal pigment epithelium seem to be irreversible. A proposed clinical grading system of oxalate maculopathy, based on a literature review, may provide clinicians with a tool to better predict visual function and prognosis.
- Lightness, chroma and hue differences on visual shade matching. [Journal Article]
- DMDent Mater 2016 Sep 7
- CONCLUSIONS: This study is an attempt to partially explain the inconsistencies between visual and instrumental shade matching and the limitations of shade guides. Visual shade matching was driven by color differences with lower chroma and hue values.
- Level of visual acuity necessary to avoid false-positives on the HRR and Ishihara color vision tests. [Journal Article]
- EJEur J Ophthalmol 2016 Sep 7; :0
- CONCLUSIONS: Based on the plate in each test that was found to be the least tolerant to blur, the average minimum VAs needed to identify the screening plates were approximately 20/180 for the Ishihara test and 20/50 for the HRR test. Identifying the demonstration plate in the Ishihara and HRR tests does not ensure FPs will be avoided.
- CCD-Based Skinning Injury Recognition on Potato Tubers (Solanum tuberosum L.): A Comparison between Visible and Biospeckle Imaging. [Journal Article]
- SSensors (Basel) 2016 Oct 18; 16(10)
- Skinning injury on potato tubers is a kind of superficial wound that is generally inflicted by mechanical forces during harvest and postharvest handling operations. Though skinning injury is pervasiv...
Skinning injury on potato tubers is a kind of superficial wound that is generally inflicted by mechanical forces during harvest and postharvest handling operations. Though skinning injury is pervasive and obstructive, its detection is very limited. This study attempted to identify injured skin using two CCD (Charge Coupled Device) sensor-based machine vision technologies, i.e., visible imaging and biospeckle imaging. The identification of skinning injury was realized via exploiting features extracted from varied ROIs (Region of Interests). The features extracted from visible images were pixel-wise color and texture features, while region-wise BA (Biospeckle Activity) was calculated from biospeckle imaging. In addition, the calculation of BA using varied numbers of speckle patterns were compared. Finally, extracted features were implemented into classifiers of LS-SVM (Least Square Support Vector Machine) and BLR (Binary Logistic Regression), respectively. Results showed that color features performed better than texture features in classifying sound skin and injured skin, especially for injured skin stored no less than 1 day, with the average classification accuracy of 90%. Image capturing and processing efficiency can be speeded up in biospeckle imaging, with captured 512 frames reduced to 125 frames. Classification results obtained based on the feature of BA were acceptable for early skinning injury stored within 1 day, with the accuracy of 88.10%. It is concluded that skinning injury can be recognized by visible and biospeckle imaging during different stages. Visible imaging has the aptitude in recognizing stale skinning injury, while fresh injury can be discriminated by biospeckle imaging.
- Neutral point testing of color vision in the domestic cat. [Journal Article]
- EEExp Eye Res 2016 Oct 5; 153:23-26
- Despite extensive study, the basic nature of feline spectral sensitivity is still unresolved. Most electrophysiological studies have demonstrated two photopic receptors within the cat's retina, one m...
Despite extensive study, the basic nature of feline spectral sensitivity is still unresolved. Most electrophysiological studies have demonstrated two photopic receptors within the cat's retina, one most sensitive to longer wavelengths near 560 nm and the other most sensitive to shorter wavelengths near 460 nm, providing the neuroretinal basis for dichromatic vision. A few studies, however, have detected a third photopic receptor most sensitive to medium wavelengths between 500 and 520 nm, overlapping in spectrally sensitivity with the feline scotopic receptor, that potentially could allow trichromatic vision. Indeed, one behavioral study has demonstrated trichromatic vision in cats, but a flaw within its experimental design raises the possibility that achromatic intensity cues might have allowed the accurate identification of medium wavelength targets. This study tested for a spectral neutral point in the domestic cat using a two-choice discrimination task. The positive targets were created using monochromatic light from various single wavelength light emitting diodes (LEDs) combined with a white light of variable intensity, while the negative targets were created using white light of variable intensity. Trials were performed with varying intensities of positive and negative targets, from brighter positive targets to brighter negative targets, to eliminate achromatic intensity cues. Two cats with prior experience with two-choice discrimination tasks, one male and one female, successfully discriminated monochromatic light from 456 nm to 497 nm and from 510 nm to 524 nm, but both failed to discriminate monochromatic light at 505 nm over multiple trials. These results provide strong evidence that cats are dichromatic with a neutral point near 505 nm. This neutral point is nearly identical to the neutral point of the human deuteuranope, making feline vision a more accurate a model for red-green colorblind individuals than normal trichromats.
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- Anticipatory eye movements and long-term memory in early infancy. [Journal Article]
- DPDev Psychobiol 2016; 58(7):841-851
- Advances in our understanding of long-term memory in early infancy have been made possible by studies that have used the Rovee-Collier's mobile conjugate reinforcement paradigm and its variants. One ...
Advances in our understanding of long-term memory in early infancy have been made possible by studies that have used the Rovee-Collier's mobile conjugate reinforcement paradigm and its variants. One function that has been attributed to long-term memory is the formation of expectations (Rovee-Collier & Hayne, 1987); consequently, a long-term memory representation should be established during expectation formation. To examine this prediction and potentially open the door on a new paradigm for exploring infants' long-term memory, using the Visual Expectation Paradigm (Haith, Hazan, & Goodman, 1988), 3-month-old infants were trained to form an expectation for predictable color and spatial information of picture events and emit anticipatory eye movements to those events. One day later, infants' anticipatory eye movements decreased in number relative to the end of training when the predictable colors were changed but not when the spatial location of the predictable color events was changed. These findings confirm that information encoded during expectation formation are stored in long-term memory, as hypothesized by Rovee-Collier and colleagues. Further, this research suggests that eye movements are potentially viable measures of long-term memory in infancy, providing confirmatory evidence for early mnemonic processes.