Showing papers on "Foveal published in 2018"

The Organization and Operation of Inferior Temporal Cortex

Abstract: Inferior temporal cortex (IT) is a key part of the ventral visual pathway implicated in object, face, and scene perception. But how does IT work? Here, I describe an organizational scheme that marries form and function and provides a framework for future research. The scheme consists of a series of stages arranged along the posterior-anterior axis of IT, defined by anatomical connections and functional responses. Each stage comprises a complement of subregions that have a systematic spatial relationship. The organization of each stage is governed by an eccentricity template, and corresponding eccentricity representations across stages are interconnected. Foveal representations take on a role in high-acuity object vision (including face recognition); intermediate representations compute other aspects of object vision such as behavioral valence (using color and surface cues); and peripheral representations encode information about scenes. This multistage, parallel-processing model invokes an innately determined organization refined by visual experience that is consistent with principles of cortical development. The model is also consistent with principles of evolution, which suggest that visual cortex expanded through replication of retinotopic areas. Finally, the model predicts that the most extensively studied network within IT-the face patches-is not unique but rather one manifestation of a canonical set of operations that reveal general principles of how IT works.

Molecular Classification and Comparative Taxonomics of Foveal and Peripheral Cells in Primate Retina

Abstract: High acuity vision in primates, including humans, is mediated by a small central retinal region called the fovea. As more accessible model organisms lack a fovea, its specialized function and dysfunction in ocular diseases remain poorly understood. We used 165,000 single-cell RNA-seq profiles to generate and validate comprehensive cellular taxonomies of macaque fovea and peripheral retina. More than 80% of >65 cell types match between the two regions, but exhibit substantial differences in proportions and gene expression, some of which we relate to functional differences. Comparison of macaque retinal types with those of mice reveals that interneuron types are tightly conserved, but that projection neuron types and programs diverge, despite conserved transcription factor codes. Key macaque types are conserved in humans, allowing mapping of cell-type and region-specific expression of >190 genes associated with 6 human retinal diseases. Our work provides a framework for comparative single-cell analysis across tissue regions and species.

Development differentially sculpts receptive fields across early and high-level human visual cortex

Abstract: Receptive fields (RFs) processing information in restricted parts of the visual field are a key property of visual system neurons. However, how RFs develop in humans is unknown. Using fMRI and population receptive field (pRF) modeling in children and adults, we determine where and how pRFs develop across the ventral visual stream. Here we report that pRF properties in visual field maps, from the first visual area, V1, through the first ventro-occipital area, VO1, are adult-like by age 5. However, pRF properties in face-selective and character-selective regions develop into adulthood, increasing the foveal coverage bias for faces in the right hemisphere and words in the left hemisphere. Eye-tracking indicates that pRF changes are related to changing fixation patterns on words and faces across development. These findings suggest a link between face and word viewing behavior and the differential development of pRFs across visual cortex, potentially due to competition on foveal coverage.

Noninvasive gene delivery to foveal cones for vision restoration

Abstract: Intraocular injection of adeno-associated viral (AAV) vectors has been an evident route for delivering gene drugs into the retina. However, gaps in our understanding of AAV transduction patterns within the anatomically unique environments of the subretinal and intravitreal space of the primate eye impeded the establishment of noninvasive and efficient gene delivery to foveal cones in the clinic. Here, we establish new vector-promoter combinations to overcome the limitations associated with AAV-mediated cone transduction in the fovea with supporting studies in mouse models, human induced pluripotent stem cell-derived organoids, postmortem human retinal explants, and living macaques. We show that an AAV9 variant provides efficient foveal cone transduction when injected into the subretinal space several millimeters away from the fovea, without detaching this delicate region. An engineered AAV2 variant provides gene delivery to foveal cones with a well-tolerated dose administered intravitreally. Both delivery modalities rely on a cone-specific promoter and result in high-level transgene expression compatible with optogenetic vision restoration. The model systems described here provide insight into the behavior of AAV vectors across species to obtain safety and efficacy needed for gene therapy in neurodegenerative disorders.

Foveal Avascular Zone and Vessel Density in Healthy Subjects: An Optical Coherence Tomography Angiography Study.

Abstract: Purpose: To report the normal characteristics and correlations of the foveal microvascular networks using optical coherence tomography angiography (OCTA) in a healthy Iranian population. Methods: Enface 3x3 OCTA images were obtained using the RTVue Avanti spectral-domain optical coherence tomography with AngioVue software (Optovue, Fremont, CA, USA). Foveal avascular zone (FAZ) area, central foveal point thickness and inner retinal thickness at the foveal center and the vascular density of the superficial retinal capillary plexus (SCP) and deep retinal capillary plexus (DCP) in the fovea were recorded. Results: Seventy normal eyes of 70 subjects (range, 9 to 71 years) were studied. Mean FAZ area was 0.32 ± 0.11 (range, 0.13-0.67) mm2 in SCP and 0.50 ± 0.13 (range, 0.19-0.94) mm2 in DCP. Mean SCP vessel density was 29.6 ± 4.7 (range, 16.3-40.3) % in the fovea. Mean DCP vessel density was 27.0 ± 5.9 (range, 15.0-45.2) % in the fovea. The FAZ area at SCP level was negatively correlated to the central subfield thickness (P Conclusion: In this study, central foveal subfield thickness was a major determinant of the FAZ size and foveal vessel density. Age was a determinant for FAZ area and whole image vessel density in DCP.

A Gated Peripheral-Foveal Convolutional Neural Network for Unified Image Aesthetic Prediction

Abstract: Learning fine-grained details is a key issue in image aesthetic assessment. Most of the previous methods extract the fine-grained details via random cropping strategy, which may undermine the integrity of semantic information. Extensive studies show that humans perceive fine-grained details with a mixture of foveal vision and peripheral vision. Fovea has the highest possible visual acuity and is responsible for seeing the details. The peripheral vision is used for perceiving the broad spatial scene and selecting the attended regions for the fovea. Inspired by these observations, we propose a Gated Peripheral-Foveal Convolutional Neural Network (GPF-CNN). It is a dedicated double-subnet neural network, i.e. a peripheral subnet and a foveal subnet. The former aims to mimic the functions of peripheral vision to encode the holistic information and provide the attended regions. The latter aims to extract fine-grained features on these key regions. Considering that the peripheral vision and foveal vision play different roles in processing different visual stimuli, we further employ a gated information fusion (GIF) network to weight their contributions. The weights are determined through the fully connected layers followed by a sigmoid function. We conduct comprehensive experiments on the standard AVA and this http URL datasets for unified aesthetic prediction tasks: (i) aesthetic quality classification; (ii) aesthetic score regression; and (iii) aesthetic score distribution prediction. The experimental results demonstrate the effectiveness of the proposed method.

Execution of saccadic eye movements affects speed perception.

Abstract: Due to the foveal organization of our visual system we have to constantly move our eyes to gain precise information about our environment. Doing so massively alters the retinal input. This is problematic for the perception of moving objects, because physical motion and retinal motion become decoupled and the brain has to discount the eye movements to recover the speed of moving objects. Two different types of eye movements, pursuit and saccades, are combined for tracking. We investigated how the way we track moving targets can affect the perceived target speed. We found that the execution of corrective saccades during pursuit initiation modifies how fast the target is perceived compared with pure pursuit. When participants executed a forward (catch-up) saccade they perceived the target to be moving faster. When they executed a backward saccade they perceived the target to be moving more slowly. Variations in pursuit velocity without corrective saccades did not affect perceptual judgments. We present a model for these effects, assuming that the eye velocity signal for small corrective saccades gets integrated with the retinal velocity signal during pursuit. In our model, the execution of corrective saccades modulates the integration of these two signals by giving less weight to the retinal information around the time of corrective saccades.

Foveal Crowding Resolved

Abstract: Crowding is the substantial interference of neighboring items on target identification. Crowding with letter stimuli has been studied primarily in the visual periphery, with conflicting results for foveal stimuli. While a cortical locus for peripheral crowding is well established (with a large spatial extent up to half of the target eccentricity), disentangling the contributing factors in the fovea is more challenging due to optical limitations. Here, we used adaptive optics (AO) to overcome ocular aberrations and employed high-resolution stimuli to precisely characterize foveal lateral interactions with high-contrast letters flanked by letters. Crowding was present, with a maximal edge-to-edge interference zone of 0.75-1.3 minutes at typical unflanked performance levels. In agreement with earlier foveal contour interaction studies, performance was non-monotonic, revealing a recovery effect with proximal flankers. Modeling revealed that the deleterious effects of flankers can be described by a single function across stimulus sizes when the degradation is expressed as a reduction in sensitivity (expressed in Z-score units). The recovery, however, did not follow this pattern, likely reflecting a separate mechanism. Additional analysis reconciles multiple results from the literature, including the observed scale invariance of center-to-center spacing, as well as the size independence of edge-to-edge spacing.

Clinical significance of ectopic inner foveal layers in patients with idiopathic epiretinal membranes

Abstract: To evaluate the relationship between the presence of ectopic inner foveal layers (EIFL), choroidal thickness, and visual acuity (VA) in patients with epiretinal membranes (ERM) staged by spectral-domain optical coherence tomography (SD-OCT). A total of 242 eyes of 121 patients with unilateral idiopathic ERM were prospectively evaluated. ERM stages were defined based on the SD-OCT staging system as stage 1: negligible morphological or anatomical disruption, retinal layers, and foveal pit are identified; stage 2: characteristic stretching of the outer nuclear layer, absence of foveal depression, retinal layers are identified; stage 3: continuous EIFL crossing the central foveal area, absence of foveal depression, retinal layers are identified; and stage 4: anatomical disruption of the fovea, continuous EIFL crossing the entire foveal area, retinal layers are distorted. Of 121 eyes with ERM, 23.1% had stage 1, 26.5% had stage 2, 39.7% had stage 3, and 10.7% had stage 4 disease. VA was better in eyes with stage 1 or 2 ERM than stage 3 or 4 ERM (p 0.05). The SD-OCT staging system according to the presence of EIFL is effective for grading retinal damage and visual loss in eyes with ERM.

Foveal hypoplasia and optical coherence tomographic imaging.

Abstract: Foveal hypoplasia is a retinal disorder in which there is a lack of full development of the morphology of the fovea. The optical coherence tomography (OCT) and functional findings are presented in relation to the underlying genetic and developmental conditions. Recent advancements of high-resolution OCT imaging have unveiled characteristics of foveal hypoplasia that were not detected by conventional imaging methods. An absence of a foveal pit does not necessarily imply poor visual acuity, and the maturation of the cone photoreceptors is important for the visual acuity. Regardless of the degree of the development of the inner retinal layers, the visual acuity can be preserved as in diseases such as Stickler syndrome that is a newly identified retinal disorder associated with foveal hypoplasia.

Functional architecture of the foveola revealed in the living primate.

Abstract: The primate foveola, with its high cone density and magnified cortical representation, is exquisitely specialized for high-resolution spatial vision. However, uncovering the wiring of retinal circuitry responsible for this performance has been challenging due to the difficulty in recording receptive fields of foveal retinal ganglion cells (RGCs) in vivo. In this study, we use adaptive optics scanning laser ophthalmoscopy (AOSLO) to image the calcium responses of RGCs in the living primate, with a stable, high precision visual stimulus that allowed us to localize the receptive fields of hundreds of foveal ganglion cells. This approach revealed a precisely radial organization of foveal RGCs, despite the many distortions possible during the extended developmental migration of foveal cells. By back projecting the line connecting RGC somas to their receptive fields, we have been able to define the ‘physiological center’ of the foveola, locating the vertical meridian separating left and right hemifields in vivo.

Perisaccadic perceptual mislocalization is different for upward saccades.

Abstract: Brief visual stimuli are robustly mislocalized around the time of saccades. Such mislocalization is thought to arise because oculomotor and visual neural maps distort space through foveal magnifica...

Calibration of peripheral perception of shape with and without saccadic eye movements

Abstract: The cortical representations of a visual object differ radically across saccades. Several studies claim that the visual system adapts the peripheral percept to better match the subsequent foveal view. Recently, Herwig, Weis, and Schneider (2015, Annals of the New York Academy of Sciences, 1339(1), 97–105) found that the perception of shape demonstrates a saccade-dependent learning effect. Here, we ask whether this learning actually requires saccades. We replicated Herwig et al.’s (2015) study and introduced a fixation condition. In a learning phase, participants were exposed to objects whose shape systematically changed during a saccade, or during a displacement from peripheral to foveal vision (without a saccade). In a subsequent test, objects were perceived as less (more) curved if they previously changed from more circular (triangular) in the periphery to more triangular (circular) in the fovea. Importantly, this pattern was seen both with and without saccades. We then tested whether a variable delay between the presentations of the peripheral and foveal objects would affect their association—hypothetically weakening it at longer delays. Again, we found that shape judgments depended on the changes experienced during the learning phase and that they were similar in both the saccade and fixation conditions. Surprisingly, they were not affected by the delay between the peripheral and foveal presentations over the range we tested. These results suggest that a general associative process, independent of saccade execution, contributes to the perception of shape across viewpoints.

Spatial summation in the human fovea: Do normal optical aberrations and fixational eye movements have an effect?

Abstract: Psychophysical inferences about the neural mechanisms supporting spatial vision can be undermined by uncertainties introduced by optical aberrations and fixational eye movements, particularly in fovea where the neuronal grain of the visual system is fine. We examined the effect of these preneural factors on photopic spatial summation in the human fovea using a custom adaptive optics scanning light ophthalmoscope that provided control over optical aberrations and retinal stimulus motion. Consistent with previous results, Ricco's area of complete summation encompassed multiple photoreceptors when measured with ordinary amounts of ocular aberrations and retinal stimulus motion. When both factors were minimized experimentally, summation areas were essentially unchanged, suggesting that foveal spatial summation is limited by postreceptoral neural pooling. We compared our behavioral data to predictions generated with a physiologically-inspired front-end model of the visual system, and were able to capture the shape of the summation curves obtained with and without pre-retinal factors using a single postreceptoral summing filter of fixed spatial extent. Given our data and modeling, neurons in the magnocellular visual pathway, such as parasol ganglion cells, provide a candidate neural correlate of Ricco's area in the central fovea.

Modeling visual search behavior of breast radiologists using a deep convolution neural network.

Abstract: Visual search, the process of detecting and identifying objects using eye movements (saccades) and foveal vision, has been studied for identification of root causes of errors in the interpretation of mammograms. The aim of this study is to model visual search behavior of radiologists and their interpretation of mammograms using deep machine learning approaches. Our model is based on a deep convolutional neural network, a biologically inspired multilayer perceptron that simulates the visual cortex and is reinforced with transfer learning techniques. Eye-tracking data were obtained from eight radiologists (of varying experience levels in reading mammograms) reviewing 120 two-view digital mammography cases (59 cancers), and it has been used to train the model, which was pretrained with the ImageNet dataset for transfer learning. Areas of the mammogram that received direct (foveally fixated), indirect (peripherally fixated), or no (never fixated) visual attention were extracted from radiologists’ visual search maps (obtained by a head mounted eye-tracking device). These areas along with the radiologists’ assessment (including confidence in the assessment) of the presence of suspected malignancy were used to model: (1) radiologists’ decision, (2) radiologists’ confidence in such decisions, and (3) the attentional level (i.e., foveal, peripheral, or none) in an area of the mammogram. Our results indicate high accuracy and low misclassification in modeling such behaviors.

Visuomotor feedback gains are modulated by gaze position.

Abstract: It is well known that directing gaze to the reach target allows the use of foveal visual feedback and extraretinal information to improve the accuracy of reaching movements. Here we demonstrate tha...

Focusing and orienting spatial attention differently modulate crowding in central and peripheral vision.

Abstract: The allocation of attentional resources to a particular location or object in space involves two distinct processes: an orienting process and a focusing process. Indeed, it has been demonstrated that performance of different visual tasks can be improved when a cue, such as a dot, anticipates the position of the target (orienting), or when its dimensions (as in the case of a small square) inform about the size of the attentional window (focusing). Here, we examine the role of these two components of visuo-spatial attention (orienting and focusing) in modulating crowding in peripheral (Experiment 1 and Experiment 3a) and foveal (Experiment 2 and Experiment 3b) vision. The task required to discriminate the orientation of a target letter "T," close to acuity threshold, presented with left and right "H" flankers, as a function of target-flanker distance. Three cue types have been used: a red dot, a small square, and a big square. In peripheral vision (Experiment 1 and Experiment 3a), we found a significant improvement with the red dot and no advantage when a small square was used as a cue. In central vision (Experiment 2 and Experiment 3b), only the small square significantly improved participants' performance, reducing the critical distance needed to recover target identification. Taken together, the results indicate a behavioral dissociation of orienting and focusing attention in their capability of modulating crowding. In particular, we confirmed that orientation of attention can modulate crowding in visual periphery, while we found that focal attention can modulate foveal crowding.

Visual function and optical coherence tomography angiography features in children born preterm

Abstract: Purpose:Preterm children have an increased risk of impaired vision from retinopathy, strabismus, and high refractive error. The aim of this study was to investigate the relationship between foveal parameters generated by optical coherence tomography angiography and visual function in preterm childre

Parallel graded attention in reading: A pupillometric study.

Abstract: There are roughly two lines of theory to account for recent evidence that word processing is influenced by adjacent orthographic information. One line assumes that multiple words can be processed simultaneously through a parallel graded distribution of visuo-spatial attention. The other line assumes that attention is strictly directed to single words, but that letter detectors are connected to both foveal and parafoveal feature detectors, as such driving parafoveal-foveal integrative effects. Putting these two accounts to the test, we build on recent research showing that the pupil responds to the brightness of covertly attended (i.e., without looking) locations in the visual field. Experiment 1 showed that foveal target word processing was facilitated by related parafoveal flanking words when these were positioned to the left and right of the target, but not when these were positioned above and below the target. Perfectly in line with this asymmetry, in Experiment 2 we found that the pupil size was contingent with the brightness of the locations of horizontally but not vertically aligned flankers, indicating that attentional resources were allocated to those words involved in the parafoveal-on-foveal effect. We conclude that orthographic parafoveal-on-foveal effects are driven by parallel graded attention.

On the advantages of foveal mechanisms for active stereo systems in visual search tasks

Abstract: In this work we study how information provided by foveated images sampled according to the log-polar transformation can be integrated over time in order to build accurate world representations and accomplish visual search tasks in an efficient manner. We focus on a specific visual information modality depth and on how to store it in a flexible memory structure. We propose a probabilistic observational model for a stereo system that relies on the Unscented Transform in order to propagate uncertainty in stereo matching, due to spatial quantization in the retina, to the 3D Cartesian domain. Probabilistic depth measurements are integrated in a novel Sensory Ego-Sphere whose topology can be biased with foveal-like distributions, according to the autonomous agent short-term tasks and goals. Furthermore, we investigate an Upper Confidence Bound algorithm for the task of simultaneously finding the closest object to the observer (visual search) and learning the surrounding environment 3D map (mapping). The performance of task execution is assessed both with a foveated log-polar sensor and a classical uniform one. The advantage of foveal vision and custom ego-sphere representations are illustrated in a series of experiments with a realistic simulator.

The spectral identity of foveal cones is preserved in hue perception.

Abstract: Organisms are faced with the challenge of making inferences about the physical world from incomplete incoming sensory information. One strategy to combat ambiguity in this process is to combine new information with prior experiences. We investigated the strategy of combining these information sources in color vision. Single cones in human subjects were stimulated and the associated percepts were recorded. Subjects rated each flash for brightness, hue, and saturation. Brightness ratings were proportional to stimulus intensity. Saturation was independent of intensity, but varied between cones. Hue, in contrast, was assigned in a stereotyped manner that was predicted by cone type. These experiments revealed that, near the fovea, long and middle wavelength sensitive cones produce sensations that can be reliably distinguished on the basis of hue, but not saturation or brightness. Taken together, these observations implicate the high-resolution, color-opponent parvocellular pathway in this low-level visual task.

Automated Foveal Detection in OCT Scans

Abstract: Fovea is a minor area about 1.5 millimeter in diameter located at the center of human retina. It is responsible for permitting 100% visual acuity and is also an important biomarker for analyzing the different retina syndromes. Fovea is dislocated in most of the retina syndromes depending upon the severity of disease progression. Optical Coherence Tomography (OCT) is a modern practice for acquisition of eye scans and visualizing the retinal changes. Usually OCT scan is acquired with fovea at the center but since OCT scan acquisition is a manual process, it is prone to errors in alignment of fovea at the center of the scan. This misaligned OCT scan creates difficulty for ophthalmologists in locating fovea especially when the disease is severely progressed. In this research, we report a computerized algorithm for detecting fovea in OCT scans. Our algorithm examines the thickness vector between the two retina layers. We analyzed three different retinal pathologies in our studies and our algorithm achieved the overall accuracy of 97.5% in localization of fovea.

Unmeasurable small size of foveal avascular zone without visual impairment in optical coherence tomography angiography.

Abstract: To report the clinical characteristics of eyes with an unmeasurable small size of foveal avascular zone (FAZ) in the optical coherence tomography angiographic (OCTA) images Two-hundred sixty-seven eyes of 255 patients (mean age 604 years) without retinal and choroidal disorders to cause any type of visual impairment were examined by optical coherence tomography angiography (OCTA; RTVue XR Avanti, Optovue, Fremont, CA) Cross-sectional images at the fovea (DRI-OCT, Topcon, Japan) and fundus autofluorescence (CX-1 MYD/NM, Canon, Japan) were also recorded from all eyes Four eyes (15%) of 3 patients (2 men, 1 woman; average age, 633 years) were found to have an unmeasurable small size of FAZ in the OCTA images The best-corrected visual acuity was better than 20/20 in all eyes Cross-sectional OCT images showed the presence of a foveal depression and the inner retinal layers in the foveal depression These inner retinal layers were detected as a hyperreflective bands at the fovea Fundus autofluorescence showed hypo-autofluorescence at the fovea as in normal eyes An unmeasurable small size of FAZ without visual impairment was detected in 15% of 267 normal eyes These eyes may be classified as low-grade foveal hypoplasia

Foveal adaptation of particles and simulation models in a foveated rendering system

Abstract: A method for implementing a graphics pipeline. The method includes generating a system of particles creating an effect in a virtual scene, the system of particles comprising a plurality of particle geometries. The method includes determining a subsystem of particles from the system of particles, the subsystem of particles comprising a subset of particle geometries taken from the plurality of particle geometries. The method includes determining a foveal region when rendering an image of the virtual scene, wherein the foveal region corresponds to where an attention of a user is directed. The method includes determining that at least one portion of the effect is located in the peripheral region for the image. The method includes rendering the subsystem of particles to generate the effect.

Visual configuration of two species of Falconidae with different foraging ecologies

Abstract: Significant interspecific differences in avian vision occur, even in congeneric species, and these have been correlated with differences in the perceptual challenges associated with foraging. Although diurnal raptors are assumed to be mainly visually guided in their foraging, they differ markedly in their foraging tactics and this may result in different visual demands. Among the Falconidae (Falconiformes), most falcons forage mainly on the wing for highly mobile prey, whereas caracaras forage on the ground for carrion and insects. We assessed whether Saker Falcon Falco cherrug and Southern Caracara Caracara plancus differ in their visual abilities by determining the visual fields and foveal characteristics of both species. Using an ophthalmoscopic reflex technique, we found a higher degree of binocular overlap in the caracaras than in the falcons. The high binocular overlap (47 degrees) of the Southern Caracara may facilitate object manipulation (e.g. moving rocks) when foraging. We used an ultra-high resolution spectral-domain optical coherence tomography to determine foveal characteristics. We found two foveas (depressions in the retina where high visual resolution is expected) in the falcons (one central and one temporal) but only a central fovea in the caracaras. The presence of a shallower temporal fovea in Saker Falcons may help to fixate visually upon a highly mobile prey item during pursuit. We conclude that these differences in visual field configurations and foveal characteristics reflect different foraging demands, suggesting that the extraction of visual information is finely tuned to the demands of their foraging tactics. (Less)