Journal articles on the topic 'Photoreceptor Spatial Distribution'
To see the other types of publications on this topic, follow the link: Photoreceptor Spatial Distribution.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 48 journal articles for your research on the topic 'Photoreceptor Spatial Distribution.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
LITHERLAND, LENORE, SHAUN P. COLLIN, and KERSTIN A. FRITSCHES. "Eye growth in sharks: Ecological implications for changes in retinal topography and visual resolution." Visual Neuroscience 26, no. 4 (July 2009): 397–409. http://dx.doi.org/10.1017/s0952523809990150.
Full textAbstract:
AbstractThe visual abilities of sharks show substantial interspecific variability. In addition, sharks may change their habitat and feeding strategy throughout life. As the eyes of sharks continue to grow throughout the animal’s lifetime, ontogenetic variability in visual ability may also occur. The topographic analysis of the photoreceptor and ganglion cell distributions can identify visual specializations and assess changes in visual abilities that may occur concurrently with eye growth. This study examines an ontogenetic series of whole-mounted retinas in two elasmobranch species, the sandbar shark, Carcharhinus plumbeus, and the shortspine spurdog, Squalus mitsukurii, to identify regional specializations mediating zones for improved spatial resolution. The study examines retinal morphology and presents data on summation ratios between photoreceptor and ganglion cell layers, anatomically determined peak spatial resolving power, and the angular extent of the visual field. Peak densities of photoreceptors and ganglion cells occur in similar retinal locations. The topographic distribution of neurons in the ganglion cell layer does not differ substantially with eye growth. However, predicted peak spatial resolution increases with eye growth from 4.3 to 8.9 cycles/deg in C. plumbeus and from 5.7 to 7.2 cycles/deg in S. mitsukurii. The topographic distribution of different-sized ganglion cells is also mapped in C. plumbeus, and a population of large ganglion cells (soma area 120–350 μm2) form a narrow horizontal streak across the retinal meridian, while the spatial distribution of ordinary-sized ganglion cells (soma area 30–120 μm2) forms an area in the central retina. Species-specific retinal specializations highlight differences in visually mediated behaviors and foraging strategies between C. plumbeus and S. mitsukurii.
2
COLLIN, SHAUN P., NATHAN S. HART, KATE M. WALLACE, JULIA SHAND, and IAN C. POTTER. "Vision in the southern hemisphere lampreyMordacia mordax: Spatial distribution, spectral absorption characteristics, and optical sensitivity of a single class of retinal photoreceptor." Visual Neuroscience 21, no. 5 (September 2004): 765–73. http://dx.doi.org/10.1017/s0952523804215103.
Full textAbstract:
The dorso-laterally located eyes of the southern hemisphere lampreyMordacia mordax(Agnatha) contain a single morphological type of retinal photoreceptor, which possesses ultrastructural characteristics of both rods and cones. This photoreceptor has a large refractile ellipsosome in the inner segment and a long cylindrical outer segment surrounded by a retinal pigment epithelium that contains two types of tapetal reflectors. The photoreceptors form a hexagonal array and attain their peak density (33,200 receptors/mm2) in the ventro-temporal retina. Using the size and spacing of the photoreceptors and direct measures of aperture size and eye dimensions, the peak spatial resolving power and optical sensitivity are estimated to be 1.7 cycles deg−1(minimum separable angle of 34′7′′) and 0.64 μm2steradian (white light) and 1.38 μm2steradian (preferred wavelength or λmax), respectively. Microspectrophotometry reveals that the visual pigment located within the outer segment is a rhodopsin with a wavelength of maximum absorbance (λmax) at 514 nm. The ellipsosome has very low absorptance (<0.05) across the measured spectrum (350–750 nm) and probably does not act as a spectral filter. In contrast to all other lampreys studied, the optimized receptor packing, the large width of the ellipsosome-bearing inner segment, together with the presence of a retinal tapetum in the photophobicMordacia, all represent adaptations for low light vision and optimizing photon capture.
3
DESMOND RAMIREZ, M., DANIEL I. SPEISER, M. SABRINA PANKEY, and TODD H. OAKLEY. "Understanding the dermal light sense in the context of integrative photoreceptor cell biology." Visual Neuroscience 28, no. 4 (July 2011): 265–79. http://dx.doi.org/10.1017/s0952523811000150.
Full textAbstract:
AbstractWhile the concept of a dermal light sense has existed for over a century, little progress has been made in our understanding of the mechanisms underlying dispersed photoreception and the evolutionary histories of dispersed photoreceptor cells. These cells historically have been difficult to locate and positively identify, but modern molecular techniques, integrated with existing behavioral, morphological, and physiological data, will make cell identification easier and allow us to address questions of mechanism and evolution. With this in mind, we propose a new classification scheme for all photoreceptor cell types based on two axes, cell distribution (aggregated vs. dispersed) and position within neural networks (first order vs. high order). All photoreceptor cells fall within one of four quadrants created by these axes: aggregated/high order, dispersed/high order, aggregated/first order, or dispersed/first order. This new method of organization will help researchers make objective comparisons between different photoreceptor cell types. Using integrative data from four major phyla (Mollusca, Cnidaria, Echinodermata, and Arthropoda), we also provide evidence for three hypotheses for dispersed photoreceptor cell function and evolution. First, aside from echinoderms, we find that animals often use dispersed photoreceptor cells for tasks that do not require spatial vision. Second, although there are both echinoderm and arthropod exceptions, we find that dispersed photoreceptor cells generally lack morphological specializations that either enhance light gathering or aid in the collection of directional information about light. Third, we find that dispersed photoreceptor cells have evolved a number of times in Metazoa and that most dispersed photoreceptor cells have likely evolved through the co-option of existing phototransduction cascades. Our new classification scheme, combined with modern investigative techniques, will help us address these hypotheses in great detail and generate new hypothesis regarding the function and evolution of dispersed photoreceptor cells.
4
LITHERLAND, LENORE, and SHAUN P. COLLIN. "Comparative visual function in elasmobranchs: Spatial arrangement and ecological correlates of photoreceptor and ganglion cell distributions." Visual Neuroscience 25, no. 4 (July 2008): 549–61. http://dx.doi.org/10.1017/s0952523808080693.
Full textAbstract:
AbstractThe topographic analysis of retinal ganglion and photoreceptor cell distributions yields valuable information for assessing the visual capabilities and behavioral ecology of vertebrates. This study examines whole-mounted retinas of four elasmobranch species, the ornate wobbegong, Orectolobus ornatus; the whitetip reef shark, Triaenodon obesus; the epaulette shark, Hemiscyllium ocellatum; and the east Australia shovelnose ray, Aptychotrema rostrata, for regional specializations mediating zones of improved visual ability. These species represent a range of lifestyles: benthic, mid-water, diurnal, and nocturnal. Both photoreceptors (visualized using differential interference contrast optics) and ganglion cells (stained with cresyl violet) in the retina are extensively sampled, and their spatial distribution is found to be nonuniform, exhibiting areae or “visual streaks.” In general, the topographic distributions of both cell populations are in register and match well with respect to the location of regions of high density. However, the location of peaks in rod and cone densities can vary within a retina, indicating that preferential sampling of different regions of the visual field may occur in photopic and scotopic vision. Anatomical measures of the optical limits of resolving power, indicated by intercone spacing, range from 3.8 to 13.1 cycles/deg. Spatial limits of resolving power, calculated from ganglion cell spacing, range from 2.6 to 4.3 cycles/deg. Summation ratios, assessed by direct comparison of cell densities of photoreceptors (input cells) and ganglion cells (output cells), at more than 150 different loci across the retina, show topographic differences in signal convergence (ranging from 25:1 to over 70:1). Species-specific retinal specializations strongly correlate to the habitat and feeding behavior of each species.
5
Schraermeyer, Ulrich, Hennig Stieve, and Michael Rack. "Cytochemical Localization of Guanylate and Adenylate Cyclase in Photoreceptor Cells of the Fly." Zeitschrift für Naturforschung C 50, no. 9-10 (October 1, 1995): 695–98. http://dx.doi.org/10.1515/znc-1995-9-1016.
Full textAbstract:
Abstract In photoreceptor cells of invertebrates light triggers an enzyme cascade in which the phos-phoinositide pathway is crucially involved. Likewise, there is growing evidence of an impor tant role of cyclic nucleotides, too. To localize these enzymes able to catalyze the formation of cGM P and cAMP, the spatial distribution of guanylate cyclase (EC 4.6.1.2) and adenylate cyclase (EC 4.6.1.1) was determined in photoreceptor cells of the fly. In photoreceptor cells of the blowfly (Calliphora erythrocephala), the electron dense reaction product of guanylate cyclase was found within the phototransducing region, the rhabdomeral microvilli and in the mitochondria. Staining was also observed throughout the cytoplasm of the microvilli. With the same cytochemical method, reaction product for adenylate cyclase was found on the tips of the photosensory membrane, and not in the cytoplasm of the rhabdomeral microvilli. The results presented here further argue for an important role of one or possibly two cyclic nucleotides in the photoreceptor cells, and possibly in the process of phototransduction of in vertebrates.
6
Seno, Keiji, Yumi Yamahama, and Fumio Hayashi. "Spatial distribution of lipid raft components in the disk membrane of frog rod photoreceptor." Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology 151, no. 4 (December 2008): 458–59. http://dx.doi.org/10.1016/j.cbpb.2008.09.047.
Full text
7
Mayhew, Terry M. "STEREOLOGY AND SOME STRUCTURAL CORRELATES OF RETINAL AND PHOTORECEPTOR CELL FUNCTION." Image Analysis & Stereology 27, no. 1 (May 3, 2011): 1. http://dx.doi.org/10.5566/ias.v28.p1-10.
Full textAbstract:
The retina is the part of the eye which detects light, transduces it into nerve impulses and plays a significant role in visual perception. Sensitivity to light is multi-factorial and depends on the properties of photopigment molecules, their synthesis and incorporation into photoreceptor membranes and the neural circuitry between photoreceptor cells, bipolar neurons and ganglion neurons. In addition, it depends on structural factors such as the absolute and relative numbers of different types of photoreceptor neurons, their subcellular morphology, their distribution across the retina and the physical dimensions (especially surface areas) and spatial arrangements of their photoreceptor membranes. At the molecular level, these membranes harbour photosensitive pigment molecules comprising transmembrane glycoproteins (opsins, which vary between photoreceptor cells) and a non-protein chromophore. Phototransduction involves a conformational change in the chromophore and activation of an opsin. A transducer G protein, transducin, lowers levels of cGMP and triggers changes in membrane ion permeability including the closure of Na+ channels. This causes the plasmalemma to become less depolarized and the relative hyperpolarization stimulates ganglion cells whose axons form the optic nerve. Phosducin is a light-regulated phosphoprotein located in inner and outer segments of rod photoreceptor cells. It modulates phototransduction by binding to beta and gamma subunits of transducin. This review briefly illustrates ways in which stereology can contribute to our understanding of these processes by providing quantitative data on photoreceptor number, disk membrane surface area and the subcellular immunolocalisation of key molecules.
8
HEMMI, JAN M., and ULRIKE GRÜNERT. "Distribution of photoreceptor types in the retina of a marsupial, the tammar wallaby (Macropus eugenii)." Visual Neuroscience 16, no. 2 (March 1999): 291–302. http://dx.doi.org/10.1017/s0952523899162102.
Full textAbstract:
Mammalian retinae generally contain low numbers of short-wavelength-sensitive cones (S-cones) and higher numbers of middle- to long-wavelength-sensitive cones (M-cones). Some recent studies found topographic differences between the different photoreceptor types and in some instances between photoreceptors and ganglion cells. To investigate this question further, we constructed topographical maps of the different photoreceptors found in an Australian marsupial, the tammar wallaby. We used two polyclonal antibodies that have been shown to label S-cones (JH455) or M-cones (JH492) in a range of mammals. In the tammar wallaby, the antisera clearly distinguish two cone types. JH455 recognizes a small subset of cones (S-cones) with a density of less than 500 cells/mm2 in the ventral retina. Their density increases towards the dorsal retina to about 1600–2000 cells/mm2. JH492 recognizes all remaining cones (M-cones), but also faintly labels most cone cells recognized by JH455. The distribution of M-cones, unlike that of the S-cones, shows a clear horizontal streak of high cell density through the central retina, just like the ganglion cells. Unlike the ganglion cells, however, the M-cones do not peak in the temporal retina but show a very broad peak (12,000–18,000 cells/mm2) in the central or even slightly nasal retina. Based on our findings, the retina of the tammar can be divided into three distinct regions: firstly, the dorsal retina, which has a low ganglion and low cone cell density but a high percentage of S-cones (30%), is thought to provide good spectral sensitivity; secondly, the central horizontal band of retina, which has a high ganglion and high cone cell density and therefore provides good spatial resolution; and thirdly, the ventral retina, which has a low ganglion cell but high cone cell density with few S-cones (5%) and is therefore thought to have a high contrast sensitivity but low acuity.
9
Barua, Arnab, Alireza Beygi, and Haralampos Hatzikirou. "Close to Optimal Cell Sensing Ensures the Robustness of Tissue Differentiation Process: The Avian Photoreceptor Mosaic Case." Entropy 23, no. 7 (July 7, 2021): 867. http://dx.doi.org/10.3390/e23070867.
Full textAbstract:
The way that progenitor cell fate decisions and the associated environmental sensing are regulated to ensure the robustness of the spatial and temporal order in which cells are generated towards a fully differentiating tissue still remains elusive. Here, we investigate how cells regulate their sensing intensity and radius to guarantee the required thermodynamic robustness of a differentiated tissue. In particular, we are interested in finding the conditions where dedifferentiation at cell level is possible (microscopic reversibility), but tissue maintains its spatial order and differentiation integrity (macroscopic irreversibility). In order to tackle this, we exploit the recently postulated Least microEnvironmental Uncertainty Principle (LEUP) to develop a theory of stochastic thermodynamics for cell differentiation. To assess the predictive and explanatory power of our theory, we challenge it against the avian photoreceptor mosaic data. By calibrating a single parameter, the LEUP can predict the cone color spatial distribution in the avian retina and, at the same time, suggest that such a spatial pattern is associated with quasi-optimal cell sensing. By means of the stochastic thermodynamics formalism, we find out that thermodynamic robustness of differentiated tissues depends on cell metabolism and cell sensing properties. In turn, we calculate the limits of the cell sensing radius that ensure the robustness of differentiated tissue spatial order. Finally, we further constrain our model predictions to the avian photoreceptor mosaic.
10
LI, BAOQIN, KELLI McKERNAN, and WEN SHEN. "Spatial and temporal distribution patterns of Na-K-2Cl cotransporter in adult and developing mouse retinas." Visual Neuroscience 25, no. 2 (March 2008): 109–23. http://dx.doi.org/10.1017/s0952523808080164.
Full textAbstract:
AbstractThe Na-K-2Cl cotransporter (NKCC) is a Cl− uptake transporter that is responsible for maintaining a Cl− equilibrium potential positive to the resting potential in neurons. If NKCC is active, GABA and glycine can depolarize neurons. In view of the abundance of GABAergic and glycinergic synapses in retina, we undertook a series of studies using immunocytochemical techniques to determine the distribution of NKCC in retinas of both developing and adult mice. We found NKCC antibody (T4) labeling present in retinas from wild-type mice, but not in NKCC1-deficient mice, suggesting that the NKCC1 subtype is a major Cl− uptake transporter in mouse retina. Strong labeling of NKCC1 was present in horizontal cells and rod-bipolar dendrites in adult mice. Interestingly, we also found that a diffuse labeling pattern was present in photoreceptor terminals. However, NKCC1 was barely detectable in the inner retina of adult mice. Using an antibody against K-Cl cotransporter 2 (KCC2), we found that KCC2, a transporter that extrudes Cl−, was primarily expressed in the inner retina. The expression of NKCC1 in developing mouse retinas was studied from postnatal day (P) 1 to P21, NKCC1 labeling first appeared in the dendrites of horizontal and rod-bipolar cells as early as P7, followed by photoreceptor terminals between P10-P14; with expression gradually increasing concomitantly with the growth of synaptic terminals and dendrites throughout retinal development. In the inner retina, NKCC1 labeling was initially observed in the inner plexiform layer at P1, but labeling diminished after P5. The developmental increase in NKCC expression only occurred in the outer retina. Our results suggest that the distal synapses and synaptogenesis in mouse retinas undergo a unique process with a high intracellular Cl− presence due to NKCC1 expression.
11
Henderson, M. A., and T. G. Northcote. "Retinal Structure of Sympatric and Allopatric Populations of Cutthroat Trout (Salmo clarki clarki) and Dolly Varden Char (Salvelinus malma) in Relation to their Spatial Distribution." Canadian Journal of Fisheries and Aquatic Sciences 45, no. 7 (July 1, 1988): 1321–26. http://dx.doi.org/10.1139/f88-155.
Full textAbstract:
Retinal structures of cutthroat trout (Salmo clarki clarki) and Dolly Varden char (Salvelinus malma) were compared to determine if these features were consistent with the different light regimes in which the species live, depending on their sympatry or allopatry in lakes. Cone cell density in sympatric trout was over twice that of sympatric char and rod cell density was slightly less. The cross-sectional size of cone cells in sympatric trout was approximately 30% less than in sympatric char. The ratios of photoreceptor cells to ganglion cells in sympatric trout and char retinas were approximately 40:1 and 80:1, respectively. There were no differences between sympatric and allopatric trout with respect to these structural features. Estimates of cone cell density, cone size, and number of photoreceptor cells per ganglion cell for allopatric char were significantly different and intermediate between those for sympatric trout and char. All four populations had similar cone cell mosaics with four paired cones surrounding each single cone. Results are considered in relation to differences in vertical distribution and feeding of sympatric and allopatric populations in three study lakes.
12
Sedmak, Tina, and Uwe Wolfrum. "Intraflagellar transport molecules in ciliary and nonciliary cells of the retina." Journal of Cell Biology 189, no. 1 (April 5, 2010): 171–86. http://dx.doi.org/10.1083/jcb.200911095.
Full textAbstract:
The assembly and maintenance of cilia require intraflagellar transport (IFT), a process mediated by molecular motors and IFT particles. Although IFT is a focus of current intense research, the spatial distribution of individual IFT proteins remains elusive. In this study, we analyzed the subcellular localization of IFT proteins in retinal cells by high resolution immunofluorescence and immunoelectron microscopy. We report that IFT proteins are differentially localized in subcompartments of photoreceptor cilia and in defined periciliary target domains for cytoplasmic transport, where they are associated with transport vesicles. IFT20 is not in the IFT core complex in photoreceptor cilia but accompanies Golgi-based sorting and vesicle trafficking of ciliary cargo. Moreover, we identify a nonciliary IFT system containing a subset of IFT proteins in dendrites of retinal neurons. Collectively, we provide evidence to implicate the differential composition of IFT systems in cells with and without primary cilia, thereby supporting new functions for IFT beyond its well-established role in cilia.
13
Nunley, Hayden, Mikiko Nagashima, Kamirah Martin, Alcides Lorenzo Gonzalez, Sachihiro C. Suzuki, Declan A. Norton, Rachel O. L. Wong, Pamela A. Raymond, and David K. Lubensky. "Defect patterns on the curved surface of fish retinae suggest a mechanism of cone mosaic formation." PLOS Computational Biology 16, no. 12 (December 15, 2020): e1008437. http://dx.doi.org/10.1371/journal.pcbi.1008437.
Full textAbstract:
The outer epithelial layer of zebrafish retinae contains a crystalline array of cone photoreceptors, called the cone mosaic. As this mosaic grows by mitotic addition of new photoreceptors at the rim of the hemispheric retina, topological defects, called “Y-Junctions”, form to maintain approximately constant cell spacing. The generation of topological defects due to growth on a curved surface is a distinct feature of the cone mosaic not seen in other well-studied biological patterns like the R8 photoreceptor array in the Drosophila compound eye. Since defects can provide insight into cell-cell interactions responsible for pattern formation, here we characterize the arrangement of cones in individual Y-Junction cores as well as the spatial distribution of Y-junctions across entire retinae. We find that for individual Y-junctions, the distribution of cones near the core corresponds closely to structures observed in physical crystals. In addition, Y-Junctions are organized into lines, called grain boundaries, from the retinal center to the periphery. In physical crystals, regardless of the initial distribution of defects, defects can coalesce into grain boundaries via the mobility of individual particles. By imaging in live fish, we demonstrate that grain boundaries in the cone mosaic instead appear during initial mosaic formation, without requiring defect motion. Motivated by this observation, we show that a computational model of repulsive cell-cell interactions generates a mosaic with grain boundaries. In contrast to paradigmatic models of fate specification in mostly motionless cell packings, this finding emphasizes the role of cell motion, guided by cell-cell interactions during differentiation, in forming biological crystals. Such a route to the formation of regular patterns may be especially valuable in situations, like growth on a curved surface, where the resulting long-ranged, elastic, effective interactions between defects can help to group them into grain boundaries.
14
Vidal, Elisa, Bokkyoo Jun, William C. Gordon, Marie-Annick Maire, Lucy Martine, Stéphane Grégoire, Spiro Khoury, et al. "Bioavailability and spatial distribution of fatty acids in the rat retina after dietary omega-3 supplementation." Journal of Lipid Research 61, no. 12 (October 30, 2020): 1733–46. http://dx.doi.org/10.1194/jlr.ra120001057.
Full textAbstract:
Spatial changes of FAs in the retina in response to different dietary n-3 formulations have never been explored, although a diet rich in EPA and DHA is recommended to protect the retina against the effects of aging. In this study, Wistar rats were fed for 8 weeks with balanced diet including either EPA-containing phospholipids (PLs), EPA-containing TGs, DHA-containing PLs, or DHA-containing TGs. Qualitative changes in FA composition of plasma, erythrocytes, and retina were evaluated by gas chromatography-flame ionization detector. Following the different dietary intakes, changes to the quantity and spatial organization of PC and PE species in retina were determined by LC coupled to MS/MS and MALDI coupled to MS imaging. The omega-3 content in the lipids of plasma and erythrocytes suggests that PLs as well as TGs are good omega-3 carriers for retina. However, a significant increase in DHA content in retina was observed, especially molecular species as di-DHA-containing PC and PE, as well as an increase in very long chain PUFAs (more than 28 carbons) following PL-EPA and TG-DHA diets only. All supplemented diets triggered spatial organization changes of DHA in the photoreceptor layer around the optic nerve. Taken together, these findings suggest that dietary omega-3 supplementation can modify the content of FAs in the rat retina.
15
Hamm, Gregory, Gareth Maglennon, Beth Williamson, Ruth Macdonald, Ann Doherty, Stewart Jones, Jayne Harris, et al. "Pharmacological inhibition of MERTK induces in vivo retinal degeneration: a multimodal imaging ocular safety assessment." Archives of Toxicology 96, no. 2 (January 1, 2022): 613–24. http://dx.doi.org/10.1007/s00204-021-03197-8.
Full textAbstract:
AbstractThe receptor tyrosine kinase, MERTK, plays an essential role in homeostasis of the retina via efferocytosis of shed outer nuclear segments of photoreceptors. The Royal College of Surgeons rat model of retinal degeneration has been linked to loss-of-function of MERTK, and together with the MERTK knock-out mouse, phenocopy retinitis pigmentosa in humans with MERTK mutations. Given recent efforts and interest in MERTK as a potential immuno-oncology target, development of a strategy to assess ocular safety at an early pre-clinical stage is critical. We have applied a state-of-the-art, multi-modal imaging platform to assess the in vivo effects of pharmacological inhibition of MERTK in mice. This involved the application of mass spectrometry imaging (MSI) to characterize the ocular spatial distribution of our highly selective MERTK inhibitor; AZ14145845, together with histopathology and transmission electron microscopy to characterize pathological and ultra-structural change in response to MERTK inhibition. In addition, we assessed the utility of a human retinal in vitro cell model to identify perturbation of phagocytosis post MERTK inhibition. We identified high localized total compound concentrations in the retinal pigment epithelium (RPE) and retinal lesions following 28 days of treatment with AZ14145845. These lesions were present in 4 of 8 treated animals, and were characterized by a thinning of the outer nuclear layer, loss of photoreceptors (PR) and accumulation of photoreceptor outer segments at the interface of the RPE and PRs. Furthermore, the lesions were very similar to that shown in the RCS rat and MERTK knock-out mouse, suggesting a MERTK-induced mechanism of PR cell death. This was further supported by the observation of reduced phagocytosis in the human retinal cell model following treatment with AZ14145845. Our study provides a viable, translational strategy to investigate the pre-clinical toxicity of MERTK inhibitors but is equally transferrable to novel chemotypes.
16
HUANG, BO, CHERYL K. MITCHELL, and DIANNA A. REDBURN-JOHNSON. "GABA and GABAA receptor antagonists alter developing cone photoreceptor development in neonatal rabbit retina." Visual Neuroscience 17, no. 6 (November 2000): 925–35. http://dx.doi.org/10.1017/s0952523800176126.
Full textAbstract:
Gamma aminobutyric acid (GABA) has been established as an important developmental signal in a number of regions of the central nervous system (CNS), including retina. Our previous studies have shown that GABAergic horizontal cells act as the initial synaptic target for developing cone photoreceptors in neonatal rabbit retina. Since intraocular injections of the GABAA receptor antagonists, picrotoxin or bicuculline, disrupt cone synaptogenesis in vivo, GABA released from horizontal cells may provide a necessary signal for cone axon growth and/or synapse formation. In the current report, we have used cultured retinal explants to examine the effects of GABAA receptor antagonists on other aspects of developing cones. These include the distribution pattern of cone cell bodies across the outer surface of the retina and the expression of GABAA receptors within both cone cell bodies and axonal processes. Peanut agglutinin (PNA), a plant lectin that specifically labels cone plasma membrane and extracellular matrix, was used to monitor cone development, and a GABAA receptor antibody against the β2/3 subunits of the protein was used to label GABAA receptors. Results showed that cones maintained in the explant culture express GABAA receptors in a temporal and spatial pattern similar to that observed in vivo, namely a low expression of receptors on cone cell bodies at postnatal day 1 (P1), peaking around P3 and diminishing by P7. Neonatal retinal explants exposed to the GABAA receptor antagonists, bicuculline (10 μM) or SR95531 (5 μM), for 24 h in culture showed disruption of the normal distribution of cone cell bodies. When GABA (100 μM) was added along with either antagonist, cone cell bodies appeared normal. Neither bicuculline nor SR95531 alone had any effect on the general morphology of other retinal layers, suggesting that these GABAA receptor antagonists at the concentrations used were not acting as nonspecific disruption agents. The effects of GABA antagonists were confined to the first week after birth with no disruption seen in P9 or adult explant cultures. These data provide a direct demonstration of the necessity for GABAergic input to cones during active synaptogenesis. As we have previously shown, GABAA receptor activation causes a substantial increase in intracellular calcium concentrations in cones and thereby could provide a mechanism by which GABA regulates cone maturation.
17
Kaluzny, Jakub J., Bartosz L. Sikorski, Grzegorz Czajkowski, Mateusz Burduk, Bartlomiej J. Kaluzny, Joanna Stafiej, and Grazyna Malukiewicz. "Photoreceptor Inner and Outer Segment Junction Reflectivity after Vitrectomy for Macula-Off Rhegmatogenous Retinal Detachment." Journal of Ophthalmology 2015 (2015): 1–7. http://dx.doi.org/10.1155/2015/451408.
Full textAbstract:
Purpose. To evaluate the spatial distribution of photoreceptor inner and outer segment junction (IS/OS) reflectivity changes after successful vitrectomy for macula-off retinal detachment (PPV-mOFF) using spectral domain optical coherence tomography (SdOCT).Methods. Twenty eyes after successful PPV-mOFF were included in the study. During a mean follow-up period of 15.3 months, SdOCT was performed four times. To evaluate the IS/OS reflectivity a four-grade scale was used.Results. At the first follow-up visit the IS/OS had very similar reflectivity in entire length of the central scan with total average value of 1,05. At the second visit the most significant increase of the reflectivity was observed in temporal and nasal parafovea with average values of 2,17 and 2,22, respectively. The third region of increased reflectivity of an average value of 2,33 appeared during the third follow-up visit and was located in the foveola. At the last follow-up visit in entire central cross section the IS/OS reflectivity exceeded grade 2 reaching the highest average values in nasal and temporal parafovea and foveola.Conclusions. A gradual increase of the IS/OS reflectivity was observed in eyes after PPV-mOFF. The process is not random and starts independently in the peripheral and central part of the macula which may be attributed to the variable regenerative potential of cones and rods.
18
Zaidi, Q., B. Spehar, and J. S. DeBonnet. "Adaptation to Variegated Scenes and Colour Constancy." Perception 25, no. 1_suppl (August 1996): 184. http://dx.doi.org/10.1068/v96l0613.
Full textAbstract:
For a visual system to possess colour constancy across varying illumination, chromatic signals from a scene must remain constant at some neural stage. We found that photoreceptor and opponent-colour signals from a large sample of natural and man-made objects under one kind of natural daylight were almost perfectly correlated with the signals from those objects under every other spectrally different phase of daylight. Therefore, in scenes consisting of many objects, the effect of illumination changes on specific colour mechanisms can be simulated by shifting all chromaticities by an additive or multiplicative constant along a theoretical axis. When the effect of the illuminant change was restricted to specific colour axes, thresholds for detecting a change in the perceived colours in a scene were significantly elevated in the presence of spatial variations along the same axis. Probe-flash threshold curves revealed that adaptation to variegated scenes is qualitatively different from independent adaptation to the constituents or to the space-average, but is similar to adaptation to prolonged temporal modulation (Shapiro and Zaidi, 1992 Vision Research32 2065 – 2076), which would be caused by small eye-movements across object boundaries. The data are consistent with a ‘response equalisation’ model, which modifies the response function of each mechanism to match the cumulative frequency distribution of its inputs (Zaidi and Shapiro, 1993 Biological Cybernetics69 415 – 428). In a variegated scene, correlations between spatially local chromatic signals across illuminants, and adaptation caused by eye movements across spatial variations, help the visual system to attenuate the perceptual effects due to changes in illumination.
19
Savy, Claudine, Axelle Simon, and Jeanine Nguyen-Legros. "Spatial geometry of the dopamine innervation in the avascular area of the human fovea." Visual Neuroscience 7, no. 5 (November 1991): 487–98. http://dx.doi.org/10.1017/s0952523800009779.
Full textAbstract:
AbstractThe dopamine (DA) innervation, labeled by tyrosine hydroxylase immunohistochemistry in a wholemounted human retina, is described in the avascular area of the fovea. Eleven DA neurons give rise to this innervation, among which five are interplexiform cells, so that the DA innervation consists of two plexuses: one is internal and is formed by the dendrites of all of the DA cells, and the other is external and is formed by the scleral processes of the interplexiform cells. Five concentric zones are delineated according to the focal plane in which the internal DA plexus is observed. The central zone 1 contains DA processes crossing in all directions. Zones 2 and 3 do not contain any cell bodies. In zone 3 the internal plexus begins to undergo a concentric arrangement, which is clearly observed in zones 4 and 5. The external DA innervation displays a different appearance in zones 1, 2, and 3, in which it consists of vertically oriented thin processes and terminals penetrating the outer nuclear layer, vs. zones 4 and 5 in which it consists of both the same type and horizontal processes lying in the outer plexiform layer. On the basis of DA-innervation appearance and distribution of labeled and unlabeled cell somata, it was concluded that zones 1, 2, and 3 contained the DA innervation of the foveola. DA processes filtering between photoreceptor cells are particularly well-observed in this region. This anatomical study of the DA innervation in the human fovea leads to a better understanding of the important role of DA in primate central vision and can be used as a reference for an approach of macular pathology.
20
Li, Hong-Sheng, and Craig Montell. "TRP and the PDZ Protein, Inad, Form the Core Complex Required for Retention of the Signalplex in Drosophila Photoreceptor Cells." Journal of Cell Biology 150, no. 6 (September 18, 2000): 1411–22. http://dx.doi.org/10.1083/jcb.150.6.1411.
Full textAbstract:
The light response in Drosophila photoreceptor cells is mediated by a series of proteins that assemble into a macromolecular complex referred to as the signalplex. The central player in the signalplex is inactivation no afterpotential D (INAD), a protein consisting of a tandem array of five PDZ domains. At least seven proteins bind INAD, including the transient receptor potential (TRP) channel, which depends on INAD for localization to the phototransducing organelle, the rhabdomere. However, the determinants required for localization of INAD are not known. In this work, we showed that INAD was required for retention rather than targeting of TRP to the rhabdomeres. In addition, we demonstrated that TRP bound to INAD through the COOH terminus, and this interaction was required for localization of INAD. Other proteins that depend on INAD for localization, phospholipase C and protein kinase C, also mislocalized. However, elimination of any other member of the signalplex had no impact on the spatial distribution of INAD. A direct interaction between TRP and INAD did not appear to have a role in the photoresponse independent of localization of multiple signaling components. Rather, the primary function of the TRP/ INAD complex is to form the core unit required for localization of the signalplex to the rhabdomeres.
21
PARRY, N. R. A., S. PLAINIS, I. J. MURRAY, and D. J. McKEEFRY. "Effect of foveal tritanopia on reaction times to chromatic stimuli." Visual Neuroscience 21, no. 3 (May 2004): 237–42. http://dx.doi.org/10.1017/s0952523804213359.
Full textAbstract:
To investigate the effect of foveal inhomogeneities on sensitivity to chromatic stimuli, we measured simple reaction times (RTs) and detection thresholds to temporally and spatially blurred isoluminant stimuli at retinal eccentricities from 0 deg to 8 deg. Three color-normal subjects participated. Contrast gain was derived from the slope of the RT versus contrast function. With a Gaussian spatial distribution (S.D. = 0.5 deg) and modulation between white (CIE x,y,L = 0.31, 0.316, 12.5 cd.m−2) and blue (MBDKL 90 deg), gain was maximal at about 2-deg eccentricity and declined by approximately 1 log unit towards the center and the periphery. The red (0 deg) and green (180 deg) cardinal axes showed maximum gain in the center, whilst the yellow (270 deg) data were intermediate. Although the spatial extent of the Gaussian spot was much larger than the S-cone free zone, we wished to determine whether foveal tritanopia was responsible for the marked drop in sensitivity to the 90-deg stimulus. To align the color vector along a tritan line, we used a smaller disk (0.3 deg) with a blurred edge and measured detection threshold, rotating the vector until minimum central sensitivity was obtained. Other workers have used transient tritanopia or minimally distinct border to similar effect. By repeating this at different locations in color space, a group of vectors were obtained. These converged near to the S-cone co-punctal point, evidence that they lay along tritan confusion lines. These threshold findings were then confirmed using the RT-derived contrast gain function. The tritan vectors were less pronounced as stimulus size increased. With the vector optimized to produce foveal tritanopia, the RT gain versus eccentricity functions for the 90-deg and 270-deg stimuli both fell markedly in the center and periphery, and sensitivity peaked at about 3-deg eccentricity. There are some similarities between these findings and the underlying photoreceptor distributions. As a result, there is a greater difference in gain between red–green and blue–yellow systems in the center than in the near periphery. We conclude that the RT versus contrast function is a sensitive index of foveal opponency.
22
Dutta, Sandip, and Martha Wilson. "Spatial Mapping of Distributed Sensors Biomimicking the Human Vision System." Electronics 10, no. 12 (June 16, 2021): 1443. http://dx.doi.org/10.3390/electronics10121443.
Full textAbstract:
Machine vision has been thoroughly studied in the past, but research thus far has lacked an engineering perspective on human vision. This paper addresses the observed and hypothetical neural behavior of the brain in relation to the visual system. In a human vision system, visual data are collected by photoreceptors in the eye, and these data are then transmitted to the rear of the brain for processing. There are millions of retinal photoreceptors of various types, and their signals must be unscrambled by the brain after they are carried through the optic nerves. This work is a forward step toward explaining how the photoreceptor locations and proximities are resolved by the brain. It is illustrated here that unlike in digital image sensors, there is no one-to-one sensor-to-processor identifier in the human vision system. Instead, the brain must go through an iterative learning process to identify the spatial locations of the photosensors in the retina. This involves a process called synaptic pruning, which can be simulated by a memristor-like component in a learning circuit model. The simulations and proposed mathematical models in this study provide a technique that can be extrapolated to create spatial distributions of networked sensors without a central observer or location knowledge base. Through the mapping technique, the retinal space with known configuration generates signals as scrambled data-feed to the logical space in the brain. This scrambled response is then reverse-engineered to map the logical space’s connectivity with the retinal space locations.
23
Luby-Phelps, Katherine, Joseph Fogerty, Sheila A. Baker, Gregory J. Pazour, and Joseph C. Besharse. "Spatial distribution of intraflagellar transport proteins in vertebrate photoreceptors." Vision Research 48, no. 3 (February 2008): 413–23. http://dx.doi.org/10.1016/j.visres.2007.08.022.
Full text
24
Rhim, Issac, Gabriela Coello-Reyes, Hee-Kyoung Ko, and Ian Nauhaus. "Maps of cone opsin input to mouse V1 and higher visual areas." Journal of Neurophysiology 117, no. 4 (April 1, 2017): 1674–82. http://dx.doi.org/10.1152/jn.00849.2016.
Full textAbstract:
Studies in the mouse retina have characterized the spatial distribution of an anisotropic ganglion cell and photoreceptor mosaic, which provides a solid foundation to study how the cortex pools from afferent parallel color channels. In particular, the mouse’s retinal mosaic exhibits a gradient of wavelength sensitivity along its dorsoventral axis. Cones at the ventral extreme mainly express S opsin, which is sensitive to ultraviolet (UV) wavelengths. Then, moving toward the retina’s dorsal extreme, there is a transition to M-opsin dominance. Here, we tested the hypothesis that the retina’s opsin gradient is recapitulated in cortical visual areas as a functional map of wavelength sensitivity. We first identified visual areas in each mouse by mapping retinotopy with intrinsic signal imaging (ISI). Next, we measured ISI responses to stimuli along different directions of the S- and M-color plane to quantify the magnitude of S and M input to each location of the retinotopic maps in five visual cortical areas (V1, AL, LM, PM, and RL). The results illustrate a significant change in the S:M-opsin input ratio along the axis of vertical retinotopy that is consistent with the gradient along the dorsoventral axis of the retina. In particular, V1 populations encoding the upper visual field responded to S-opsin contrast with 6.1-fold greater amplitude than to M-opsin contrast. V1 neurons encoding lower fields responded with 4.6-fold greater amplitude to M- than S-opsin contrast. The maps in V1 and higher visual areas (HVAs) underscore the significance of a wavelength sensitivity gradient for guiding the mouse’s behavior. NEW & NOTEWORTHY Two elements of this study are particularly novel. For one, it is the first to quantify cone inputs to mouse visual cortex; we have measured cone input in five visual areas. Next, it is the first study to identify a feature map in the mouse visual cortex that is based on well-characterized anisotropy of cones in the retina; we have identified maps of opsin selectivity in five visual areas.
25
Malchow, R. P., H. H. Qian, H. Ripps, and J. E. Dowling. "Structural and functional properties of two types of horizontal cell in the skate retina." Journal of General Physiology 95, no. 1 (January 1, 1990): 177–98. http://dx.doi.org/10.1085/jgp.95.1.177.
Full textAbstract:
Two morphologically distinct types of horizontal cell have been identified in the all-rod skate retina by light- and electron-microscopy as well as after isolation by enzymatic dissociation. The external horizontal cell is more distally positioned in the retina and has a much larger cell body than does the internal horizontal cell. However, both external and internal horizontal cells extend processes to the photoreceptor terminals where they end as lateral elements adjacent to the synaptic ribbons within the terminal invaginations. Whole-cell voltage-clamp studies on isolated cells similar in appearance to those seen in situ showed that both types displayed five separate voltage-sensitive conductances: a TTX-sensitive sodium conductance, a calcium current, and three potassium-mediated conductances (an anomalous rectifier, a transient outward current resembling an A current, and a delayed rectifier). There was, however, a striking difference between external and internal horizontal cells in the magnitude of the current carried by the anomalous rectifier. Even after compensating for differences in the surface areas of the two cell types, the sustained inward current elicited by hyperpolarizing voltage steps was a significantly greater component of the current profile of external horizontal cells. A difference between external and internal horizontal cells was seen also in the magnitudes of their TEA-sensitive currents; larger currents were usually obtained in recordings from internal horizontal cells. However, the currents through these K+ channels were quite small, the TEA block was often judged to be incomplete, and except for depolarizing potentials greater than or equal to +20 mV (i.e., outside the normal operating range of horizontal cells), this current did not provide a reliable indicator of cell type. The fact that two classes of horizontal cell can be distinguished by their electrophysiological responses, as well as by their morphological appearance and spatial distribution in the retina, suggests that they may play different roles in the processing of visual information within the retina.
26
Garza-Gisholt, Eduardo, Ryan M. Kempster, Nathan S. Hart, and Shaun P. Collin. "Visual Specializations in Five Sympatric Species of Stingrays from the Family Dasyatidae." Brain, Behavior and Evolution 85, no. 4 (2015): 217–32. http://dx.doi.org/10.1159/000381091.
Full textAbstract:
The eyes of five ray species (Taeniura lymma, Neotrygon kuhlii, Pastinachus atrus, Himantura uarnak and Urogymnus asperrimus) from the same taxonomic family (Dasyatidae) and the same geographic region (Ningaloo Reef, Western Australia) were studied to identify differences in retinal specializations that may reflect niche specialization. The topographic distributions of photoreceptors (rods and all cones) and ganglion cells were assessed and used to identify localized peaks in cell densities that indicate specializations for acute vision. These data were also used to calculate summation ratios of photoreceptors to ganglion cells in each species and estimate the anatomical spatial resolving power of the eye. Subtle differences in the distribution of retinal neurons appear to be related to the ecology of these closely related species of stingrays. The main specialization in the retinal cell density distribution is the dorsal streak that allows these animals to scan the substrate for potential prey. The blue-spotted fantail ray, T. lymma, showed the highest peak density of rods (86,700 rods mm-2) suggesting a specialization for scotopic vision. The highest peak density of cones (9,970 cones mm-2) was found in H. uarnak, and the highest peak density of ganglion cells (4,500 cells mm-2) was found in P. atrus. The proportion of rods to cones in the dorsal streak was higher in the two smaller species (12.5-14:1 in T. lymma and N. kuhlii) than the larger stingrays (6-8:1 in P. atrus, H. uarnak and U. asperrimus). Visual specializations in different sympatric species are subtle but may reflect specializations to specific ecological niches.
27
ZHANG, JIAN, ZHUO YANG, and SAMUEL M. WU. "Immuocytochemical analysis of spatial organization of photoreceptors and amacrine and ganglion cells in the tiger salamander retina." Visual Neuroscience 21, no. 2 (March 2004): 157–66. http://dx.doi.org/10.1017/s0952523804042075.
Full textAbstract:
In the present study, using double- or triple-label immunocytochemistry in conjunction with confocal microscopy, we aimed to examine the population and distribution of photoreceptors, GABAergic and glycinergic amacrine cells, and ganglion cells, which are basic but important parameters for studying the structure–function relationship of the salamander retina. We found that the outer nuclear layer (ONL) contained 82,019 ± 3203 photoreceptors, of which 52% were rods and 48% were cones. The density of photoreceptors peaked at ∼8000 cells/mm2 in the ventral and dropped to ∼4000 cells/mm2 in the dorsal retina. In addition, the rod/cone ratio was less than 1 in the central retina but larger than 1 in the periphery. Moreover, in the proximal region of the inner nuclear layer (INL3), the total number of cells was 50,576 ± 8400. GABAergic and glycinergic amacrine cells made up approximately 78% of all cells in this layer, including 43% GABAergic, 32% glycinergic, and 3% GABA/glycine colocalized amacrine cells. The density of these amacrine cells was ∼6500 cells/mm2 in the ventral and ∼3200 cells/mm2 in the dorsal area. The ratio of GABAergic to glycinergic amacrine cells was larger than 1. Furthermore, in the ganglion cell layer (GCL), among a total of 36,007 ± 2010 cells, ganglion cells accounted for 65.7 ± 1.5% of the total cells, whereas displaced GABAergic and glycinergic amacrine cells comprised about 4% of the cells in this layer. The ganglion cell density was ∼1800 cells/mm2 in the ventral and ∼600 cells/mm2 in the dorsal retina. Our data demonstrate that all three major cell types are not uniformly distributed across the salamander retina. Instead, they exhibit a higher density in the ventral than in the dorsal retina and their spatial arrangement is associated with the retinal topography. These findings provide a basic anatomical reference for the electrophysiological study of this species.
28
VELDHOEN, KATHY, W. TED ALLISON, NIK VELDHOEN, BRADLEY R. ANHOLT, CAREN C. HELBING, and CRAIG W. HAWRYSHYN. "Spatio-temporal characterization of retinal opsin gene expression during thyroid hormone-induced and natural development of rainbow trout." Visual Neuroscience 23, no. 2 (March 2006): 169–79. http://dx.doi.org/10.1017/s0952523806232139.
Full textAbstract:
The abundance and spatial distribution of retinal cone photoreceptors change during thyroid hormone (TH)-induced and natural development of rainbow trout (Oncorhynchus mykiss). These changes are thought to allow the fish to adapt to different photic environments throughout its life history. To date, the ontogeny of rainbow trout cone photoreceptors has been examined using physiological and morphological approaches. In this study, we extended these observations by measuring opsin gene expression in retinal quadrants during natural and TH-induced development. Gene expression during natural development was investigated in retinae from fish at both parr and smolt stages. The role of TH in modulating opsin gene expression was determined in TH-treated parr and control fish sampled after two, nine, and 22 days of treatment. Total RNA was isolated from each retinal quadrant and steady-state opsin mRNA levels were measured using reverse transcriptase real-time quantitative polymerase chain reaction (QPCR) analysis. Expression of ultraviolet-sensitive opsin (SWS1), rod opsin (RH1), middle wavelength-sensitive opsin (RH2), and long wavelength-sensitive opsin (LWS) transcripts vary spatially in the parr retina. Smolts, compared to parr, had downregulated SWS1 expression in all quadrants, lower LWS expression dorsally, higher RH1 expression nasally, and higher RH2 expression dorsally. In TH-treated parr, SWS1 opsin expression was downregulated in the nasal quadrants by two days. SWS1 displayed the greatest degree of downregulation in all quadrants after nine days of treatment, with an increase in short wavelength-sensitive (SWS2) and RH2 opsin mRNA expression in the temporal quadrants. This study reveals that opsin genes display spatially significant differences within rainbow trout retina in their level of mRNA expression, and that regulation of opsin expression is a dynamic process that is influenced by TH. This is particularly evident for SWS1 gene expression in parr following TH-induced and natural development.
29
Bodrogi, P., QT Vinh, and TQ Khanh. "Correlations among lighting quality metrics for interior lighting." Lighting Research & Technology 51, no. 8 (December 18, 2018): 1192–207. http://dx.doi.org/10.1177/1477153518818856.
Full textAbstract:
Correlations between selected lighting quality metrics derived from the spectrum were computed and interpreted for a representative set of interior light source spectra. Metrics of brightness and the melanopic effect were strongly correlated with each other but not with the metrics of colour quality. Results can be used to establish a two-dimensional diagram with criterion values to ensure the general user acceptance of a lighting system. This diagram can be extended in the future by further metrics describing light intensity and spatial and temporal light distributions. Relationships between lighting quality metrics and colorimetric quantities as well as photoreceptor signal values are also shown.
30
Curcio, Christine A., and Kenneth R. Sloan. "Packing geometry of human cone photoreceptors: Variation with eccentricity and evidence for local anisotropy." Visual Neuroscience 9, no. 2 (August 1992): 169–80. http://dx.doi.org/10.1017/s0952523800009639.
Full textAbstract:
AbstractDisorder in the packing geometry of the human cone mosaic is believed to help alleviate spatial aliasing effects. To characterize cone packing geometry, we gathered positions of cone inner segments at seven locations along four primary and two oblique meridians in an adult human retina. We generated statistical descriptors based on the distribution of distances and angles to Voronoi neighbors. Parameters of a compressed-jittered model were fit to the actual mosaic. Local anisotropics were investigated using correlograms. We find that (1) median distance between Voronoi neighbors increases with eccentricity, but the minimum distance is constant (6–8 μm) across peripheral retina; (2) the cone mosaic is least compressed and jittered at the edge of the foveal rod-free zone; (3) disorder in the foveal center resembles that described by Pu m et al. (1990); (4) cone spacing is 10–15% less in one direction than in the orthogonal direction; and (5) cone spacing is greater in the radial direction (along meridians) than in the tangential direction (along lines of isoeccentricity). The nearly constant minimum distance implies that high spatial frequencies may be sampled even in peripheral retina. Local anisotropy of the cone mosaic is discussed in relation to the growth of the primate retina during development and to the orientation biases of retinal ganglion cells.
31
El-Mansi, Ahmed A., M. A. Al-Kahtani, K. M. Al-Sayyad, E. A. Ahmed, and A. R. Gad. "Visual adaptability and retinal characterization of the Egyptian fruit bat (Rousettus aegyptiacus, Pteropodidae): New insights into photoreceptors spatial distribution and melanosomal activity." Micron 137 (October 2020): 102897. http://dx.doi.org/10.1016/j.micron.2020.102897.
Full text
32
Hart, Nathan S. "Vision in the peafowl (Aves:Pavo cristatus)." Journal of Experimental Biology 205, no. 24 (December 15, 2002): 3925–35. http://dx.doi.org/10.1242/jeb.205.24.3925.
Full textAbstract:
SUMMARYThe visual sense of the Indian blue-shouldered peafowl Pavo cristatus was investigated with respect to the spectral absorption characteristics of the retinal photoreceptors, the spectral transmittance of the ocular media and the topographic distribution of cells in the retinal ganglion cell layer. Microspectrophotometry revealed a single class of rod,four spectrally distinct types of single cone and a single class of double cone. In the case of the single cone types, which contained visual pigments with wavelengths of maximum absorbance (λmax) at 424, 458,505 and 567 nm, spectral filtering by the ocular media and the different cone oil droplets with which each visual pigment is associated gives predicted peak spectral sensitivities of 432, 477, 537 and 605 nm, respectively. Topographic analysis of retinal ganglion cell distribution revealed a large central area of increased cell density (at peak, 35,609 cells mm-2) with a poorly defined visual streak extending nasally. The peafowl has a calculated maximum spatial resolution (visual acuity) in the lateral visual field of 20.6 cycles degrees-1. These properties of the peafowl eye are discussed with respect to its visual ecology and are compared with those of other closely related species.
33
Coimbra, João Paulo, Consolate Kaswera-Kyamakya, Emmanuel Gilissen, Paul R. Manger, and Shaun P. Collin. "The Retina of Ansorge's Cusimanse (Crossarchus ansorgei): Number, Topography and Convergence of Photoreceptors and Ganglion Cells in Relation to Ecology and Behavior." Brain, Behavior and Evolution 86, no. 2 (2015): 79–93. http://dx.doi.org/10.1159/000433514.
Full textAbstract:
The family Herpestidae (cusimanses and mongooses) is a monophyletic radiation of carnivores with remarkable variation in microhabitat occupation and diel activity, but virtually nothing is known about how they use vision in the context of their behavioral ecology. In this paper, we measured the number and topographic distribution of neurons (rods, cones and retinal ganglion cells) and estimated the spatial resolving power of the eye of the diurnal, forest-dwelling Ansorge's cusimanse (Crossarchus ansorgei). Using retinal wholemounts and stereology, we found that rods are more numerous (42,500,000; 92%) than cones (3,900,000; 8%). Rod densities form a concentric and dorsotemporally asymmetric plateau that matches the location and shape of a bright yellow tapetum lucidum located within the dorsal aspect of the eye. Maximum rod density (340,300 cells/mm2) occurs within an elongated plateau below the optic disc that corresponds to a transitional region between the tapetum lucidum and the pigmented choroid. Cone densities form a temporal area with a peak density of 44,500 cells/mm2 embedded in a weak horizontal streak that matches the topographic distribution of retinal ganglion cells. Convergence ratios of cones to retinal ganglion cells vary from 50:1 in the far periphery to 3:1 in the temporal area. With a ganglion cell peak density of 13,400 cells/mm2 and an eye size of 11 mm in axial length, we estimated upper limits of spatial resolution of 7.5-8 cycles/degree, which is comparable to other carnivores such as hyenas. In conclusion, we suggest that the topographic retinal traits described for Ansorge's cusimanse conform to a presumed carnivore retinal blueprint but also show variations that reflect its specific ecological needs.
34
Bernadin, Florent, Thomas Schwitzer, Vincent Laprevote, and Raymund Schwan. "T132. RETINAL GANGLION CELLS DYSFUNCTIONS IN SCHIZOPHRENIA PATIENTS." Schizophrenia Bulletin 46, Supplement_1 (April 2020): S280—S281. http://dx.doi.org/10.1093/schbul/sbaa029.692.
Full textAbstract:
Abstract Background Structural and functional retinal anomalies are documented in neurologic, substance use and psychiatric disorders. In schizophrenia, flash electroretinogram (fERG) measures have revealed photoreceptors, bipolar cells and retinal ganglion cells (RGC) dysfunctions. To date, no study has explored RGC using a pattern electroretinogram (pERG) protocol as recommended by the International Society for Clinical Electrophysiology of Vision (ISCEV) standards for RGC measurements. We aim to study retinal functional responses of the photoreceptors and RGC in schizophrenia patients in comparison with healthy controls. Methods fERG conducted in scotopic (dark-adapted 0.01 and dark-adapted 3.0 ERG) and photopic conditions (light-adapted 3.0 ERG) and pERG were recorded in schizophrenia patients (n=29) and healthy controls (n=29). PERG provides the measurements of 2 waves: the P50 wave which arises in RGC with a contribution of bipolar cells and relates to the spatial distribution and density of the RGC bodies and the N95 wave which represents ganglion cell activity. Results fERG results showed a decrease in the b-wave amplitude (t(51)=-3.4, p<.05, d=0.63) (dark-adapted 0.01 ERG), a-wave amplitude (t(48)=4.7, p<.001, d =1.33) (dark-adapted 3.0 ERG), b-wave amplitude (t(48)=-2.8, p<.005, d=0.78) (dark-adapted 3.0 ERG), a-wave amplitude (t(52)=2.8, p<.001, d=0.29) (light-adapted 3.0 ERG) in schizophrenia patients compared to controls. We found as well a significant decrease of the a-wave implicit time (t(52)=-2.5, p<.05, d =1.19) (light-adapted 3.0 ERG) in schizophrenia patients compared to controls. pERG results showed a significant increase of the P50 (t(55)=2.1, p<.05, d=0.55) and a significant increase of the N95 implicit time in schizophrenia patients compared with controls (t(55)=4.2; p<.001, d=0.66). Discussion Our results replicate previous findings regarding photoreceptors and bipolar cells dysfunction in schizophrenia patients. pERG results demonstrate a delay in transmission of action potentials by the ganglion cells along the visual pathway via the optic nerve and the lateral geniculate nucleus to the visual cortex in schizophrenia patients which could support alterations in cerebral visual processing in schizophrenia.
35
Cameron, David A. "Asymmetric retinal growth: Evidence for regulation by a retinotopic mechanism." Visual Neuroscience 13, no. 3 (May 1996): 493–500. http://dx.doi.org/10.1017/s0952523800008166.
Full textAbstract:
AbstractAdult teleost retinas grow throughout life, in part by the addition of cells from an encircling, proliferative neuroepithelium. In some species, this proliferative growth is asymmetric around the retina. The present study evaluated two hypotheses regarding asymmetric proliferative growth in adult green sunfish retina: (1) the generation of rod photoreceptors in central retina from proliferative rod precursor cells is also asymmetric; and (2) asymmetric proliferative growth patterns are regulated by mechanisms that are organized retinotopically and are independent of body-axis coordinates. In all retinas examined, rod precursor distribution and rod production were asymmetric, and both were in coarse spatial register with the asymmetric pattern of cellular addition at the retinal margin. In adult eyes that were surgically rotated, the asymmetric patterns of proliferative growth were present and appropriate for the retina's prerotation orientation. The results suggest that proliferative growth at both marginal and central adult sunfish retina is asymmetric, and that these asymmetric growth patterns are regulated by a retinotopic mechanism that is independent of body-axis coordinates.
36
MacLeish, Peter R., and Colin A. Nurse. "Ion Channel Compartments in Photoreceptors: Evidence From Salamander Rods With Intact and Ablated Terminals." Journal of Neurophysiology 98, no. 1 (July 2007): 86–95. http://dx.doi.org/10.1152/jn.00775.2006.
Full textAbstract:
Vertebrate photoreceptors are highly polarized sensory cells in which several different ionic currents have been characterized. In the present study we used whole cell voltage-clamp and optical imaging techniques, the former combined with microsurgical manipulations, and simultaneous recording of membrane current and intracellular calcium signals to investigate the spatial distribution of ion channels within isolated salamander rods. In recordings from intact rods with visible terminals, evidence for five previously identified ionic currents was obtained. These include two Ca2+-dependent, i.e., a Ca2+-dependent chloride current [ ICl(Ca)] and a large-conductance Ca2+- and voltage-dependent K+ or BK current [ IK(Ca)], and three voltage-dependent currents, i.e., a delayed-rectifier type current [ IK(V)], a hyperpolarization-activated cation current ( Ih), and a dihydropyridine-sensitive L-type calcium current ( ICa). Of these, ICl(Ca) was highly correlated with the presence of a terminal; rods with visible terminals expressed ICl(Ca) without exception ( n = 125), whereas approximately 71% of rods (40/56) without visible terminals lacked ICl(Ca). More significantly, ICl(Ca) was absent from all rods ( n = 33) that had their terminals ablated, and recordings from the same cell before and after terminal ablation led, in all cases ( n =10), to the loss of ICl(Ca). In contrast, IK(Ca), IK(V), and Ih remained largely intact after terminal ablation, suggesting that they arose principally from ion channels located in the soma and/or inner segment. The outward IK(Ca) in terminal-ablated rods was reversibly suppressed on “puffing” a Ca2+-free extracellular solution over the soma and was appreciably enhanced by the L-type Ca2+ channel agonist, Bay K 8644 (0.1–2 μM). These data indicate that rod photoreceptors possess discrete targeting mechanisms that preferentially sort ion channels mediating ICl(Ca) to the terminal.
37
Jacoby, Jason, Matthew A. Kreitzer, Simon Alford, and Robert Paul Malchow. "Fluorescent imaging reports an extracellular alkalinization induced by glutamatergic activation of isolated retinal horizontal cells." Journal of Neurophysiology 111, no. 5 (March 1, 2014): 1056–64. http://dx.doi.org/10.1152/jn.00768.2013.
Full textAbstract:
Extracellular acidification induced by retinal horizontal cells has been hypothesized to underlie lateral feedback inhibition onto vertebrate photoreceptors. To test this hypothesis, the H+-sensitive fluorophore 5-hexadecanoylaminofluorescein (HAF) was used to measure changes in H+ from horizontal cells isolated from the retina of the catfish. HAF staining conditions were modified to minimize intracellular accumulation of HAF and maximize membrane-associated staining, and ratiometric fluorescent imaging of cells displaying primarily membrane-associated HAF fluorescence was conducted. Challenge of such HAF-labeled cells with glutamate or the ionotropic glutamate receptor agonist kainate produced an increase in the fluorescence ratio, consistent with an alkalinization response of +0.12 pH units and +0.23 pH units, respectively. This alkalinization was blocked by the AMPA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), the L-type calcium channel blocker nifedipine, and lanthanum. The alkalinization reported by HAF was consistent with extracellular alkalinizations detected in previous studies using self-referencing H+-selective microelectrodes. The spatial distribution of the kainate-induced changes in extracellular H+ was also examined. An overall global alkalinization around the cell was observed, with no obvious signs of discrete centers of acidification. Taken together, these data argue against the hypothesis that glutamatergic-induced efflux of protons from horizontal cells mediates lateral feedback inhibition in the outer retina.
38
Milam, Ann H., Dennis M. Dacey, and Alexander M. Dizhoor. "Recoverin immunoreactivity in mammalian cone bipolar cells." Visual Neuroscience 10, no. 1 (January 1993): 1–12. http://dx.doi.org/10.1017/s0952523800003175.
Full textAbstract:
AbstractHuman, macaque monkey, and rat retinas were immunostained with a polyclonal antibody preparation against purified recoverin, a 23-kD calcium-binding protein isolated from bovine retina that localizes to rods and cones (Dizhoor et al., 1991). In addition to immunoreactive photoreceptors, we have identified subpopulations of recoverin-positive bipolar cells in all three species. Results from immunostaining with progressive dilutions of anti-recoverin and preadsorption of the antibody with a dilution series of purified recoverin showed that photoreceptors and bipolar cells had similar affinities for the antibody and suggested that the molecule recognized by the antibody in both cell types is recoverin. Immunoreactivity for recoverin and protein kinase C, a selective marker for all rod bipolar cells, was found in separate bipolar cell populations. Recoverin immunoreactivity is therefore a characteristic of certain cone bipolar cell types.In rat retina, anti-recoverin labeled two morphologically distinct subpopulations of cone bipolar cells whose axonal arbors stratified at different depths in the inner plexiform layer (IPL). The bipolar cells labeled with anti-recoverin did not correspond to those that were reactive for calbindin, another cone bipolar cell marker.Human and monkey retinas also had two populations of cone bipolar cells that were recoverin-positive. One population showed a distinct pattern of narrow bistratification at the outer border of the IPL and a regular mosaic arrangement of its axonal arbors, suggesting that the entire population of a single cone bipolar type was labeled. Cell density, dendritic morphology, and axonal-field size and stratification indicate that anti-recoverin selectively stains the flat midget (presumed OFF-center) cone bipolar cell type observed previously in Golgi preparations. By contrast the second bipolar cell population had axonal stratification in the inner half of the IPL and showed an unusual but consistent morphology and spatial distribution. Individual cells were intensely stained but were present at an extremely low density (~2−5 cells/mm2). These cells had multibranched dendritic trees characteristic of the diffuse bipolar cell class, but very small axonal fields in the size range of the midget bipolar class. Neither of the two recoverin-positive bipolar cell types in monkey was labeled with anti-calbindin or anti-cholecystokinin. An antibody preparation against bovine pineal hydroxyindole-O-methyltransferase (HIOMT) labeled photoreceptors and bipolar cells that closely resembled the recoverin-positive bipolar cells in human and rat retinas. Preadsorption of this antibody preparation with purified recoverin abolished immunostaining of the bipolar cells, suggesting that the anti-HIOMT preparation contains antibodies against recoverin, which is known to be present in the bovine pineal gland.
39
Westheimer, Gerald. "Directional sensitivity of the retina: 75 years of Stiles–Crawford effect." Proceedings of the Royal Society B: Biological Sciences 275, no. 1653 (September 2, 2008): 2777–86. http://dx.doi.org/10.1098/rspb.2008.0712.
Full textAbstract:
The reduction of the brightness when a light beam's entry into the eye is shifted from the centre to the edge of the pupil has from the outset been shown to be due to a change in luminous efficiency of radiation when it is incident obliquely on the retina. The phenomenon is most prominent in photopic vision and this has concentrated attention on the properties of retinal cones, where responsibility has yet to be assigned to factors such as differences in shape, fine structure and configuration, and membrane anchoring of photopigment molecules. Geometrical optics and waveguide formulations have been applied to the question of how light is guided in receptors, but details of their geometry and optical parameters even if they become available will make calculations complex and of only moderate generality. In practice, the diminution of oblique light helps visual performance by reducing deleterious influence of ocular aberrations and of glare caused by light scattering when the pupil is wide. Receptor orientation can come into play in ocular conditions due to mechanical disturbance and has been shown to have potentiality as a tool for clinical diagnosis. Currently, open questions include microanatomical and molecular differences between rods and cones, the coupling of the optical image of the eye with the transducing apparatus in the photoreceptors, possible phototropism and more convincing methods of estimating the actual spatial distribution of photon events as it affects visual resolution.
40
Laughlin, S. B. "The role of sensory adaptation in the retina." Journal of Experimental Biology 146, no. 1 (September 1, 1989): 39–62. http://dx.doi.org/10.1242/jeb.146.1.39.
Full textAbstract:
Adaptation, a change in response to a sustained stimulus, is a widespread property of sensory systems, occurring at many stages, from the most peripheral energy-gathering structures to neural networks. Adaptation is also implemented at many levels of biological organization, from the molecule to the organ. Despite adaptation's diversity, it is fruitful to extract some unifying principles by considering well-characterized components of the insect visual system. A major function of adaptation is to increase the amount of sensory information an organism uses. The amount of information available to an organism is ultimately defined by its environment and its size. The amount of information collected depends upon the ways in which an organism samples and transduces signals. The amount of information that is used is further limited by internal losses during transmission and processing. Adaptation can increase information capture and reduce internal losses by minimizing the effects of physical and biophysical constraints. Optical adaptation mechanisms in compound eyes illustrate a common trade-off between energy (quantum catch) and acuity (sensitivity to changes in the distribution of energy). This trade-off can be carefully regulated to maximize the information gathered (i.e. the number of pictures an eye can reconstruct). Similar trade-offs can be performed neurally by area summation mechanisms. Light adaptation in photoreceptors introduces the roles played by cellular constraints in limiting the available information. Adaptation mechanisms prevent saturation and, by trading gain for temporal acuity, increase the rate of information uptake. By minimizing the constraint of nonlinear summation (imposed by membrane conductance mechanisms) a cell's sensitivity follows the Weber-Fechner law. Thus, a computationally advantageous transformation is generated in response to a cellular constraint. The synaptic transfer of signals from photoreceptors to second-order neurones emphasizes that the cellular constraints of nonlinearity, noise and dynamic range limit the transmission of information from cell to cell. Synaptic amplification is increased to reduce the effects of noise but this resurrects the constraint of dynamic range. Adaptation mechanisms, both confined to single synapses and distributed in networks, remove spatially and temporally redundant signal components to help accommodate more information within a single cell. The net effect is a computationally advantageous removal of the background signal. Again, the cellular constraints on information transfer have dictated a computationally advantageous operation.
41
Hay, Abbie C., Jonathan Sandoval-Castillo, Georgina M. Cooke, Ning L. Chao, and Luciano B. Beheregaray. "Riverscape Genomics Clarifies Neutral and Adaptive Evolution in an Amazonian Characin Fish (Triportheus albus)." Frontiers in Ecology and Evolution 10 (March 4, 2022). http://dx.doi.org/10.3389/fevo.2022.825406.
Full textAbstract:
Understanding the role of natural selection in the evolution of wild populations is challenging due to the spatial complexity of natural systems. The richest diversity of freshwater fishes in the world is found in the Amazon Basin, a system where marked hydrochemical differences exist at the interface of major rivers with distinct “water colors” (i.e., black, white, and clear water). We hypothesize that divergent natural selection associated with these “aquatic ecotones” influences population-level adaptive divergence in the non-migratory Amazonian fish fauna. This hypothesis was tested using a landscape genomics framework to compare the relative contribution of environmental and spatial factors to the evolutionary divergence of the Amazonian characin fish Triportheus albus. The framework was based on spatial data, in situ hydrochemical measurements, and 15,251 filtered SNPs (single nucleotide polymorphisms) for T. albus sampled from three major Amazonian rivers. Gradient Forest, redundancy analysis (RDA) and BayPass analyses were used to test for signals of natural selection, and model-based and model-free approaches were used to evaluate neutral population differentiation. After controlling for a signal of neutral hierarchical structure which was consistent with the expectations for a dendritic system, variation in turbidity and pH were key factors contributing to adaptive divergence. Variation in genes involved in acid-sensitive ion transport pathways and light-sensitive photoreceptor pathways was strongly associated with pH and turbidity variability. This study improves our understanding of how natural selection and neutral evolution impact on the distribution of aquatic biodiversity from the understudied and ecologically complex Amazonia.
42
Rhim, Issac, and Ian Nauhaus. "Joint representations of color and form in mouse visual cortex described by random pooling from rods and cones." Journal of Neurophysiology, January 25, 2023. http://dx.doi.org/10.1152/jn.00138.2022.
Full textAbstract:
Spatial transitions in color can aid any visual perception task, and its neural representation - the "integration of color and form" - is thought to begin at primary visual cortex (V1). An integration of color and form is untested in mouse V1, yet studies show that the ventral retina provides the necessary substrate from green-sensitive rods and UV-sensitive cones. Here, we used two-photon imaging in V1 to measure spatial frequency (SF) tuning along four axes of rod and cone contrast space, including luminance and color. We first reveal that V1's sensitivity to color is similar to luminance, yet average SF tuning is significantly shifted lowpass for color. Next, guided by linear models, we used SF tuning along all four color axes to estimate the proportion of neurons that fall into classic models of color opponency - "single-", "double-", and "non-opponent". Few neurons (~6%) fit criteria for double-opponency, which are uniquely tuned for chromatic borders. Most of the population can be described as a unimodal distribution ranging from strongly single-opponent to non-opponent. Consistent with recent studies of the rodent and primate retina, our V1 data is well-described by a simple model in which ON and OFF channels to V1 sample the photoreceptor mosaic randomly. Finally, an analysis comparing color opponency to preferred orientation and retinotopy further validates rods, and not cone M-opsin, as opponent with cone S-opsin in the upper visual field.
43
Pegoraro, Mirko, Emily Sayegh Rezek, Bettina Fishman, and Eran Tauber. "Nucleotide Variation in Drosophila cryptochrome Is Linked to Circadian Clock Function: An Association Analysis." Frontiers in Physiology 13 (February 17, 2022). http://dx.doi.org/10.3389/fphys.2022.781380.
Full textAbstract:
Cryptochrome (CRY) is a conserved protein associated with the circadian clock in a broad range of organisms, including plants, insects, and mammals. In Drosophila, cry is a pleiotropic gene that encodes a blue light-dedicated circadian photoreceptor, as well as an electromagnetic field sensor and a geotaxis behavior regulator. We have generated a panel of nearly-isogenic strains that originated from various wild populations and which carry different natural alleles of cry. Sequencing of these alleles revealed substantial polymorphism, the functional role of which was elusive. To link this natural molecular diversity to gene function, we relied on association mapping. Such analysis revealed two major haplogroups consisting of six linked nucleotides associated with circadian phase (haplotypes All1/All2). We also generated a maximum-likelihood gene-tree that uncovered an additional pair of haplogroups (B1/B2). Behavioral analysis of the different haplotypes indicated significant effect on circadian phase and period, as well on the amount of activity and sleep. The data also suggested substantial epistasis between the All and B haplogroups. Intriguingly, circadian photosensitivity, assessed by light-pulse experiments, did not differ between the genotypes. Using CRISPR-mediated transgenic flies, we verified the effect of B1/B2 polymorphism on circadian phase. The transgenic flies also exhibited substantially different levels of cry transcription. We, moreover, analyzed the geographical distribution of the B1/B2 haplotypes, focusing on a 12 bp insertion/deletion polymorphism that differentiates the two haplotypes. Analysis of cry sequences in wild populations across Europe revealed a geographical cline of B1/B2 indel frequency, which correlated with seasonal bioclimatic variables. This spatial distribution of cry polymorphism reinforces the functional importance of these haplotypes in the circadian system and local adaptation.
44
Bonelli, Roberto, Sasha M. Woods, Sarah Lockwood, Paul N. Bishop, Kamron N. Khan, Melanie Bahlo, Brendan R. E. Ansell, and Marcus Fruttiger. "Spatial distribution of metabolites in the retina and its relevance to studies of metabolic retinal disorders." Metabolomics 19, no. 2 (February 6, 2023). http://dx.doi.org/10.1007/s11306-022-01969-6.
Full textAbstract:
Abstract Introduction The primate retina has evolved regional specialisations for specific visual functions. The macula is specialised towards high acuity vision and is an area that contains an increased density of cone photoreceptors and signal processing neurons. Different regions in the retina display unique susceptibility to pathology, with many retinal diseases primarily affecting the macula. Objectives To better understand the properties of different retinal areas we studied the differential distribution of metabolites across the retina. Methods We conducted an untargeted metabolomics analysis on full-thickness punches from three different regions (macula, temporal peri-macula and periphery) of healthy primate retina. Results Nearly half of all metabolites identified showed differential abundance in at least one comparison between the three regions. Furthermore, mapping metabolomics results from macula-specific eye diseases onto our region-specific metabolite distributions revealed differential abundance defining systemic metabolic dysregulations that were region specific. Conclusions The unique metabolic phenotype of different retinal regions is likely due to the differential distribution of different cell types in these regions reflecting the specific metabolic requirements of each cell type. Our results may help to better understand the pathobiology of retinal diseases with region specificity.
45
Clark, Ashley M., Janis Intoy, Michele Rucci, and Martina Poletti. "Eye drift during fixation predicts visual acuity." Proceedings of the National Academy of Sciences 119, no. 49 (November 28, 2022). http://dx.doi.org/10.1073/pnas.2200256119.
Full textAbstract:
Visual acuity is commonly assumed to be determined by the eye optics and spatial sampling in the retina. Unlike a camera, however, the eyes are never stationary during the acquisition of visual information; a jittery motion known as ocular drift incessantly displaces stimuli over many photoreceptors. Previous studies have shown that acuity is impaired in the absence of retinal image motion caused by eye drift. However, the relation between individual drift characteristics and acuity remains unknown. Here, we show that a) healthy emmetropes exhibit a large variability in their amount of drift and that b) these differences profoundly affect the structure of spatiotemporal signals to the retina. We further show that c) the spectral distribution of the resulting luminance modulations strongly correlates with individual visual acuity and that d) natural intertrial fluctuations in the amount of drift modulate acuity. As a consequence, in healthy emmetropes, acuity can be predicted from the motor behavior elicited by a simple fixation task, without directly measuring it. These results shed new light on how oculomotor behavior contributes to fine spatial vision.
46
Tashiro, Juliana H., Dora F. Ventura, and Einat Hauzman. "Morphological Plasticity of the Retina of Viperidae Snakes Is Associated With Ontogenetic Changes in Ecology and Behavior." Frontiers in Neuroanatomy 15 (January 26, 2022). http://dx.doi.org/10.3389/fnana.2021.770804.
Full textAbstract:
Snakes of the Viperidae family have retinas adapted to low light conditions, with high packaging of rod-photoreceptors containing the rhodopsin photopigment (RH1), and three types of cone-photoreceptors, large single and double cones with long-wavelength sensitive opsins (LWS), and small single cones with short-wavelength sensitive opsins (SWS1). In this study, we compared the density and distribution of photoreceptors and ganglion cell layer (GCL) cells in whole-mounted retinas of two viperid snakes, the lancehead Bothrops jararaca and the rattlesnake Crotalus durissus, and we estimated the upper limits of spatial resolving power based on anatomical data. The ground-dwelling C. durissus inhabits savannah-like habitats and actively searches for places to hide before using the sit-and-wait hunting strategy to ambush rodents. B. jararaca inhabits forested areas and has ontogenetic changes in ecology and behavior. Adults are terrestrial and use similar hunting strategies to those used by rattlesnakes to prey on rodents. Juveniles are semi-arboreal and use the sit-and-wait strategy and caudal luring to attract ectothermic prey. Our analyses showed that neuronal densities were similar for the two species, but their patterns of distribution were different between and within species. In adults and juveniles of C. durissus, cones were distributed in poorly defined visual streaks and rods were concentrated in the dorsal retina, indicating higher sensitivity in the lower visual field. In adults of B. jararaca, both cones and rods were distributed in poorly defined visual streaks, while in juveniles, rods were concentrated in the dorsal retina and cones in the ventral retina, enhancing sensitivity in the lower visual field and visual acuity in the upper field. The GCL cells had peak densities in the temporal retina of C. durissus and adults of B. jararaca, indicating higher acuity in the frontal field. In juveniles of B. jararaca, the peak density of GCL cells in the ventral retina indicates better acuity in the upper field. The estimated visual acuity varied from 2.3 to 2.8 cycles per degree. Our results showed interspecific differences and suggest ontogenetic plasticity of the retinal architecture associated with changes in the niche occupied by viperid snakes, and highlight the importance of the retinal topography for visual ecology and behavior of snakes.
47
"Real-time performance of a movement-sensitive neuron in the blowfly visual system: coding and information transfer in short spike sequences." Proceedings of the Royal Society of London. Series B. Biological Sciences 234, no. 1277 (September 22, 1988): 379–414. http://dx.doi.org/10.1098/rspb.1988.0055.
Full textAbstract:
We develop model-independent methods for characterizing the information carried by particular features of a neural spike train as it encodes continuously varying stimuli. These methods consist, in essence, of an inverse statistical approach; instead of asking for the statistics of neural responses to a given stimulus we describe the probability distribution of stimuli that give rise to a certain short pattern of spikes. These ‘response-conditional ensembles’ contain all the information about the stimulus that a hypothetical observer of the spike train may obtain. The structure of these distributions thus provides a quantitative picture of the neural code, and certain integrals of these distributions determine the absolute information in bits carried by a given spike sequence. These methods are applied to a movement-sensitive neuron (H1) in the visual system of the blowfly Calliphora erythrocephala . The stimulus is chosen as the time-varying angular velocity of a (spatially) random pattern, and we consider segments of the spike train of up to three spikes with specified spike-intervals. We demonstrate that, with extensive analysis, a single experiment of roughly one hour’s duration is sufficient to provide reliable estimates of the relevant probability distributions. From the experimentally determined probability distributions we are able to draw several conclusions. (1) Under the conditions of our experiment, observation of a single spike carries roughly 0.36 bits of information, but spike pairs carry an interval-dependent signal that can be much larger than 0.72 bits; estimates of the total information capacity are in rough agreement with the maximum possible capacity given the signal-to-noise characteristics of the photoreceptors. (2) On average a single spike signals the occurrence of a velocity waveform that is positive (movement in the excitatory direction) at all times before the spike, whereas spike pairs can signal both positive and negative velocities, depending on the inter-spike interval. (3) Although inter-spike intervals are crucial in extracting all the coded information, the code is robust to several millisecond errors in the estimate of spike arrival times. (4) Short spike sequences give reliable information about specific features of the stimulus waveform, and this specificity can be quantified. (5) Our results suggest approximate strategies for reading the neural code – reconstructing the stimulus from observations of the spike train – and some preliminary reconstructions are presented. Some tentative attempts are made to relate our results to the more general questions of coding and computation in the nervous system.
48
"Visual edge detection in the honeybee and its chromatic properties." Proceedings of the Royal Society of London. B. Biological Sciences 238, no. 1293 (January 22, 1990): 321–30. http://dx.doi.org/10.1098/rspb.1990.0002.
Full textAbstract:
Free-flying bees were trained to collect a reward of sugar-water at one of several discs placed horizontally on a contrasting background. In subsequent tests the reward was removed and the behaviour of the bees was observed and recorded on video-tape while they landed on the experimental arrangement in search of the reward. The spatial distribution of the landings was analysed to measure the detectability of the discs and attractiveness of their boundaries, as compared to the interior regions. The results reveal that, while landing on figures, bees pay special attention to the edges. Even though the reward is placed at a randomly chosen location within the figure during training, the bees show a distinct preference for landing near the boundary of the figure. The bees’ preference for edges is restricted to figures with boundaries that provide contrast to the green-sensitive receptors. When the boundaries contain no green contrast, the edge preference disappears. In this situation, landings continue to occur mainly within the figure, but they tend to be distributed randomly over its entire surface. Thus, whereas colour information can mediate the detection of objects per se , the detection of edges, at least in the context of landing on a figure, is a colour-blind performance that is driven primarily by signals from the bee’s green-sensitive photoreceptors. This finding has interesting parallels in primate vision, where edge detection is also colour-blind. On the basis of these findings, we propose that edges provide cues that play an important role in guiding landing manouevres towards objects of interest, such as flowers.