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Visual Neuroscience

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https://www.readbyqxmd.com/read/27485367/novel-method-using-3-dimensional-segmentation-in-spectral-domain-optical-coherence-tomography-imaging-in-the-chick-reveals-defocus-induced-regional-and-time-sensitive-asymmetries-in-the-choroidal-thickness
#1
Diane R Nava, Bhavna Antony, L I Zhang, Michael D Abràmoff, Christine F Wildsoet
Studies into the mechanisms underlying the active emmetropization process by which neonatal refractive errors are corrected, have described rapid, compensatory changes in the thickness of the choroidal layer in response to imposed optical defocus. While high frequency A-scan ultrasonography, as traditionally used to characterize such changes, offers good resolution of central (on-axis) changes, evidence of local retinal control mechanisms make it imperative that more peripheral, off-axis changes also be tracked...
January 2016: Visual Neuroscience
https://www.readbyqxmd.com/read/27485271/type-specific-photoreceptor-loss-in-pigeons-after-disruption-of-parasympathetic-control-of-choroidal-blood-flow-by-the-medial-subdivision-of-the-nucleus-of-edinger-westphal
#2
A Reiner, T T Wong, C C Nazor, N Del Mar, M E C Fitzgerald
The medial part of the nucleus of Edinger-Westphal (EWM) in birds mediates light-regulated adaptive increases in choroidal blood flow (ChBF). We sought to characterize the effect of loss of EWM-mediated ChBF regulation on photoreceptor health in pigeons housed in either moderate intensity diurnal or constant light (CL). Photoreceptor abundance following complete EWM destruction was compared to that following a lesion in the pupil control circuit (as a control for spread of EWM lesions to the nearby pupil-controlling lateral EW) or following no EW damage...
January 2016: Visual Neuroscience
https://www.readbyqxmd.com/read/27485162/early-suppression-effect-in-human-primary-visual-cortex-during-kanizsa-illusion-processing-a-magnetoencephalographic-evidence
#3
Boris V Chernyshev, Platon K Pronko, Tatiana A Stroganova
Detection of illusory contours (ICs) such as Kanizsa figures is known to depend primarily upon the lateral occipital complex. Yet there is no universal agreement on the role of the primary visual cortex in this process; some existing evidence hints that an early stage of the visual response in V1 may involve relative suppression to Kanizsa figures compared with controls. Iso-oriented luminance borders, which are responsible for Kanizsa illusion, may evoke surround suppression in V1 and adjacent areas leading to the reduction in the initial response to Kanizsa figures...
January 2016: Visual Neuroscience
https://www.readbyqxmd.com/read/27485069/scotopic-vision-in-the-monkey-is-modulated-by-the-g-protein-coupled-receptor-55
#4
Joseph Bouskila, Vanessa Harrar, Pasha Javadi, Christian Casanova, Yoshio Hirabayashi, Ichiro Matsuo, Jyunpei Ohyama, Jean-François Bouchard, Maurice Ptito
The endogenous cannabinoid system plays important roles in the retina of mice and monkeys via their classic CB1 and CB2 receptors. We have previously reported that the G protein-coupled receptor 55 (GPR55), a putative cannabinoid receptor, is exclusively expressed in rod photoreceptors in the monkey retina, suggesting its possible role in scotopic vision. To test this hypothesis, we recorded full-field electroretinograms (ERGs) after the intravitreal injection of the GPR55 agonist lysophosphatidylglucoside (LPG) or the selective GPR55 antagonist CID16020046 (CID), under light- and dark-adapted conditions...
January 2016: Visual Neuroscience
https://www.readbyqxmd.com/read/27484961/methods-for-investigating-the-local-spatial-anisotropy-and-the-preferred-orientation-of-cones-in-adaptive-optics-retinal-images
#5
Robert F Cooper, Marco Lombardo, Joseph Carroll, Kenneth R Sloan, Giuseppe Lombardo
The ability to noninvasively image the cone photoreceptor mosaic holds significant potential as a diagnostic for retinal disease. Central to the realization of this potential is the development of sensitive metrics for characterizing the organization of the mosaic. Here we evaluated previously-described and newly-developed (Fourier- and Radon-based) methods of measuring cone orientation in simulated and real images of the parafoveal cone mosaic. The proposed algorithms correlated well across both simulated and real mosaics, suggesting that each algorithm provides an accurate description of photoreceptor orientation...
January 2016: Visual Neuroscience
https://www.readbyqxmd.com/read/27484854/neural-architecture-of-the-transient-on-directionally-selective-class-iib1-ganglion-cells-in-rabbit-retina-partly-co-stratified-with-starburst-amacrine-cells
#6
Edward V Famiglietti
Recent physiological studies coupled with intracellular staining have subdivided ON directionally selective (DS) ganglion cells of rabbit retina into two types. One exhibits more "transient" and more "brisk" responses (ON DS-t), and the other has more "sustained' and more "sluggish" responses (ON DS-s), although both represent the same three preferred directions and show preference for low stimulus velocity, as reported in previous studies of ON DS ganglion cells in rabbit retina. ON DS-s cells have the morphology of ganglion cells previously shown to project to the medial terminal nucleus (MTN) of the accessory optic system, and the MTN-projecting, class IVus1 cells have been well-characterized previously in terms of their dendritic morphology, branching pattern, and stratification...
January 2016: Visual Neuroscience
https://www.readbyqxmd.com/read/27471951/cacna1s-expression-in-mouse-retina-novel-isoforms-and-antibody-cross-reactivity-with-gpr179
#7
Nazarul Hasan, Thomas A Ray, Ronald G Gregg
Cacna1s encodes the α1S subunit (Cav1.1) of voltage-dependent calcium channels, and is required for normal skeletal and cardiac muscle function, where it couples with the ryanodine receptor to regulate muscle contraction. Recently CACNA1S was reported to be expressed on the tips of retinal depolarizing bipolar cells (DBCs) and colocalized with metabotropic glutamate receptor 6 (mGluR6), which is critical to DBC signal transduction. Further, in mGluR6 knockout mice, expression at this location is down regulated...
January 2016: Visual Neuroscience
https://www.readbyqxmd.com/read/26923645/noninvasive-imaging-of-the-thirteen-lined-ground-squirrel-photoreceptor-mosaic
#8
Benjamin Sajdak, Yusufu N Sulai, Christopher S Langlo, Gabriel Luna, Steven K Fisher, Dana K Merriman, Alfredo Dubra
Ground squirrels are an increasingly important model for studying visual processing, retinal circuitry, and cone photoreceptor function. Here, we demonstrate that the photoreceptor mosaic can be longitudinally imaged noninvasively in the 13-lined ground squirrel (Ictidomys tridecemlineatus) using confocal and nonconfocal split-detection adaptive optics scanning ophthalmoscopy using 790 nm light. Photoreceptor density, spacing, and Voronoi analysis are consistent with that of the human cone mosaic. The high imaging success rate and consistent image quality in this study reinforce the ground squirrel as a practical model to aid drug discovery and testing through longitudinal imaging on the cellular scale...
2016: Visual Neuroscience
https://www.readbyqxmd.com/read/26923500/multi-nucleate-retinal-pigment-epithelium-cells-of-the-human-macula-exhibit-a-characteristic-and-highly-specific-distribution
#9
Austin C Starnes, Carrie Huisingh, Gerald McGwin, Kenneth R Sloan, Zsolt Ablonczy, R Theodore Smith, Christine A Curcio, Thomas Ach
BACKGROUND: The human retinal pigment epithelium (RPE) is reportedly 3% bi-nucleated. The importance to human vision of multi-nucleated (MN)-RPE cells could be clarified with more data about their distribution in central retina. METHODS: Nineteen human RPE-flatmounts (9 ≤ 51 years, 10 > 80 years) were imaged at 12 locations: 3 eccentricities (fovea, perifovea, near periphery) in 4 quadrants (superior, inferior, temporal, nasal). Image stacks of lipofuscin-attributable autofluorescence and phalloidin labeled F-actin cytoskeleton were obtained using a confocal fluorescence microscope...
2016: Visual Neuroscience
https://www.readbyqxmd.com/read/26750628/comparative-sequence-analyses-of-rhodopsin-and-rpe65-reveal-patterns-of-selective-constraint-across-hereditary-retinal-disease-mutations
#10
Frances E Hauser, Ryan K Schott, Gianni M Castiglione, Alexander Van Nynatten, Alexander Kosyakov, Portia L Tang, Daniel A Gow, Belinda S W Chang
Retinitis pigmentosa (RP) comprises several heritable diseases that involve photoreceptor, and ultimately retinal, degeneration. Currently, mutations in over 50 genes have known links to RP. Despite advances in clinical characterization, molecular characterization of RP remains challenging due to the heterogeneous nature of causal genes, mutations, and clinical phenotypes. In this study, we compiled large datasets of two important visual genes associated with RP: rhodopsin, which initiates the phototransduction cascade, and the retinoid isomerase RPE65, which regenerates the visual cycle...
2016: Visual Neuroscience
https://www.readbyqxmd.com/read/26923349/glyr%C3%AE-2-not-glyr%C3%AE-3-modulates-the-receptive-field-surround-of-off-retinal-ganglion-cells
#11
Chi Zhang, Regina D Nobles, Maureen A McCall
Receptive fields (RFs) of most retinal ganglion cells (RGCs) consist of an excitatory center and suppressive surround. The RF center arises from the summation of excitatory bipolar cell glutamatergic inputs, whereas the surround arises from lateral inhibitory inputs. In the retina, both gamma amino butyric acid (GABA) and glycine are inhibitory neurotransmitters. A clear role for GABAergic inhibition modulating the RGC RF surround has been demonstrated across species. Glycinergic inhibition is more commonly associated with RF center modulation, although there is some evidence that it may contribute to the RF surround...
2015: Visual Neuroscience
https://www.readbyqxmd.com/read/26581040/controversies-about-the-visual-areas-located-at-the-anterior-border-of-area-v2-in-primates
#12
REVIEW
Ricardo Gattass, Bruss Lima, Juliana G M Soares, Leslie G Ungerleider
Anatomical and electrophysiological studies have provided us with detailed information regarding the extent and topography of the primary (V1) and secondary (V2) visual areas in primates. The consensus about the V1 and V2 maps, however, is in sharp contrast with controversies regarding the organization of the cortical areas lying immediately rostral to V2. In this review, we address the contentious issue of the extent of the third visual area (V3). Specifically, we will argue for the existence of both ventral (V3v) and dorsal (V3d) segments of V3, which are located, respectively, adjacent to the anterior border of ventral and dorsal V2...
2015: Visual Neuroscience
https://www.readbyqxmd.com/read/26579566/co-localization-of-glutamic-acid-decarboxylase-and-vesicular-gaba-transporter-in-cytochrome-oxidase-patches-of-macaque-striate-cortex
#13
Daniel L Adams, John R Economides, Jonathan C Horton
The patches in primary visual cortex constitute hot spots of metabolic activity, manifested by enhanced levels of cytochrome oxidase (CO) activity. They are also labeled preferentially by immunostaining for glutamic acid decarboxylase (GAD), γ-aminobutyric acid (GABA), and parvalbumin. However, calbindin shows stronger immunoreactivity outside patches. In light of this discrepancy, the distribution of the vesicular GABA transporter (VGAT) was examined in striate cortex of two normal macaques. VGAT immunoreactivity was strongest in layers 4B, 4Cα, and 5...
2015: Visual Neuroscience
https://www.readbyqxmd.com/read/26423511/a-cortical-locus-for-anisotropic-overlay-suppression-of-stimuli-presented-at-fixation
#14
Bruce C Hansen, Bruno Richard, Kristin Andres, Aaron P Johnson, Benjamin Thompson, Edward A Essock
Human contrast sensitivity for narrowband Gabor targets is suppressed when superimposed on narrowband masks of the same spatial frequency and orientation (referred to as overlay suppression), with suppression being broadly tuned to orientation and spatial frequency. Numerous behavioral and neurophysiological experiments have suggested that overlay suppression originates from the initial lateral geniculate nucleus (LGN) inputs to V1, which is consistent with the broad tuning typically reported for overlay suppression...
January 2015: Visual Neuroscience
https://www.readbyqxmd.com/read/26423343/retinotopic-organization-of-extrastriate-cortex-in-the-owl-monkey-dorsal-and-lateral-areas
#15
Martin I Sereno, Colin T McDonald, John M Allman
Dense retinotopy data sets were obtained by microelectrode visual receptive field mapping in dorsal and lateral visual cortex of anesthetized owl monkeys. The cortex was then physically flatmounted and stained for myelin or cytochrome oxidase. Retinotopic mapping data were digitized, interpolated to a uniform grid, analyzed using the visual field sign technique-which locally distinguishes mirror image from nonmirror image visual field representations-and correlated with the myelin or cytochrome oxidase patterns...
January 2015: Visual Neuroscience
https://www.readbyqxmd.com/read/26423219/nonretinotopic-visual-processing-in-the-brain
#16
REVIEW
David Melcher, Maria Concetta Morrone
A basic principle in visual neuroscience is the retinotopic organization of neural receptive fields. Here, we review behavioral, neurophysiological, and neuroimaging evidence for nonretinotopic processing of visual stimuli. A number of behavioral studies have shown perception depending on object or external-space coordinate systems, in addition to retinal coordinates. Both single-cell neurophysiology and neuroimaging have provided evidence for the modulation of neural firing by gaze position and processing of visual information based on craniotopic or spatiotopic coordinates...
January 2015: Visual Neuroscience
https://www.readbyqxmd.com/read/26423121/corticocortical-connection-patterns-reveal-two-distinct-visual-cortical-areas-bordering-dorsal-v2-in-marmoset-monkey
#17
Janelle Jeffs, Frederick Federer, Alessandra Angelucci
The organization of the cortex located immediately anterior to the second visual area (V2), i.e., the third tier visual cortex, remains controversial, especially in New World primates. In particular, there is lack of consensus regarding the exact location and extent of the lower visual quadrant representation of the third visual area V3 (or ventrolateral posterior -VLP - of a different nomenclature). Microelectrode and connectional mapping studies have revealed the existence of an upper visual quadrant representation abutting dorsal V2 anteriorly, and bordered medially and laterally by representations of the lower visual quadrant...
January 2015: Visual Neuroscience
https://www.readbyqxmd.com/read/26241957/the-medial-parietal-occipital-areas-in-the-macaque-monkey
#18
REVIEW
Michela Gamberini, Patrizia Fattori, Claudio Galletti
The number, location, extent, and functional properties of the cortical areas that occupy the medial parieto-occipital cortex (mPOC) have been, and still is, a matter of scientific debate. The mPOC is a convoluted region of the brain that presents a high level of individual variability, and the fact that many areas of mPOC are located within very deep sulci further limits the possibility to investigate their anatomo-functional properties. In the present review, we summarize the location and extent of mPOC areas in the macaque brain as obtained by architectural, connectional, and functional data...
January 2015: Visual Neuroscience
https://www.readbyqxmd.com/read/26241905/specificity-of-brain-reactions-to-second-order-visual-stimuli
#19
Vitaly V Babenko, Pavel N Ermakov
The second-order visual mechanisms perform the operation of integrating the spatially distributed local visual information. Their organization is traditionally considered within the framework of the filter-rectify-filter model. These are the second-order filters that provide the ability to detect texture gradients. However, the question of the mechanisms' selectivity to the modulation dimension remains open. The aim of this investigation is to answer the above question by using visual evoked potentials (VEPs)...
January 2015: Visual Neuroscience
https://www.readbyqxmd.com/read/26241901/identification-of-a-new-mutant-allele-grm6-nob7-for-complete-congenital-stationary-night-blindness
#20
Haohua Qian, Rui Ji, Ronald G Gregg, Neal S Peachey
Electroretinogram (ERG) studies identified a new mouse line with a normal a-wave but lacking the b-wave component. The ERG phenotype of this new allele, nob7, matched closely that of mouse mutants for Grm6, Lrit3, Trpm1, and Nyx, which encode for proteins expressed in depolarizing bipolar cells (DBCs). To identify the underlying mutation, we first crossed nob7 mice with Grm6 nob3 mutants and measured the ERGs in offspring. All the offspring lacked the b-wave, indicating that nob7 is a new allele for Grm6: Grm6 nob7 ...
January 2015: Visual Neuroscience
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