Function Of Visual System Research Articles

Melatonin Prevents Non-image-Forming Visual System Alterations Induced by Experimental Glaucoma in Rats.

Glaucoma is a blindness-causing disease that involves selective damage to retinal ganglion cells (RGCs) and their axons. A subset of RGCs expressing the photopigment melanopsin regulates non-image-forming visual system functions, such as pupillary light reflex and circadian rhythms. We analyzed the effect of melatonin on the non-image-forming visual system alterations induced by experimental glaucoma. For this purpose, male Wistar rats were weekly injected with vehicle or chondroitin sulfate into the eye anterior chamber. The non-image-forming visual system was analyzed in terms of (1) melanopsin-expressing RGC number, (2) anterograde transport from the retina to the olivary pretectal nucleus and the suprachiasmatic nuclei, (3) blue- and white light-induced pupillary light reflex, (4) light-induced c-Fos expression in the suprachiasmatic nuclei, (5) daily rhythm of locomotor activity, and (6) mitochondria in melanopsin-expressing RGC cells. Melatonin prevented the effect of experimental glaucoma on melanopsin-expressing RGC number, blue- and white light-induced pupil constriction, retina-olivary pretectal nucleus, and retina- suprachiasmatic nuclei communication, light-induced c-Fos expression in the suprachiasmatic nuclei, and alterations in the locomotor activity daily rhythm. In addition, melatonin prevented the effect of glaucoma on melanopsin-expressing RGC mitochondrial alterations. These results support that melatonin protected the non-image-forming visual system against glaucoma, probably through a mitochondrial protective mechanism.

Electrophysiological Recording for Study of Xenopus Retinotectal Circuitry.

The innervation of the optic tectum of Xenopus by retinal ganglion cells controls visual information processing and behavioral output. Several indicators can be used to evaluate the functional inputs/outputs of tectal neurons, such as spontaneous activity, visually evoked currents, temporal receptive fields, and spatial receptive fields. Analysis of multiple functional properties in the same neurons allows increased understanding of mechanisms underlying visual system function and plasticity. Patch-clamp recordings combined with gene expression or morpholino-mediated knockdown techniques have been especially powerful in the study of specific genes during development and circuit function. The protocol described here provides instructions for performing in vivo electrophysiological recordings from individual tectal neurons to study retinotectal circuitry in the developing Xenopus tectum.

Serial reproduction reveals the geometry of visuospatial representations

An essential function of the human visual system is to locate objects in space and navigate the environment. Due to limited resources, the visual system achieves this by combining imperfect sensory information with a belief state about locations in a scene, resulting in systematic distortions and biases. These biases can be captured by a Bayesian model in which internal beliefs are expressed in a prior probability distribution over locations in a scene. We introduce a paradigm that enables us to measure these priors by iterating a simple memory task where the response of one participant becomes the stimulus for the next. This approach reveals an unprecedented richness and level of detail in these priors, suggesting a different way to think about biases in spatial memory. A prior distribution on locations in a visual scene can reflect the selective allocation of coding resources to different visual regions during encoding ("efficient encoding"). This selective allocation predicts that locations in the scene will be encoded with variable precision, in contrast to previous work that has assumed fixed encoding precision regardless of location. We demonstrate that perceptual biases covary with variations in discrimination accuracy, a finding that is aligned with simulations of our efficient encoding model but not the traditional fixed encoding view. This work demonstrates the promise of using nonparametric data-driven approaches that combine crowdsourcing with the careful curation of information transmission within social networks to reveal the hidden structure of shared visual representations.

Effects of vestibular spontaneous nystagmus on visual smooth pursuit function

Objective: The aim of the study is to analyze the effects of vestibular spontaneous nystagmus(SN) on the smooth pursuit function of visual ocularmotor system. Methods: A total of 46 patients with acute unilateral peripheral vestibular syndrome with SN (26 cases of vestibular neuritis, 6 cases of Ramsay Hunt Syndrome (RHS) with vertigo, 14 cases of sudden deafness with vertigo) were included in this work. In the study group, the results of SPT and SN test with videonystagmography(VNG) were also reviewed. Taking SPT parameters, the influence of SN intensity on SPT gain, asymmetry and waveform and their correlation were analyzed.SPSS19.0 software was used for statistical analysis. Results: Among the 46 patients, there were 36 cases of SN pointing to the healthy side(SN intensity range of 2.68°/s-32.53°/s), and 10 cases of SN pointing to the affected side (SN intensity range of 2.66°/s-16.54°/s). SN intensity was divided into 3 groups, including light(0.50°/s-5.00°/s), medium(5.01°/s-10.00°/s) and strong(>10.01°/s), accounting for 14 cases(30.4%), 18 cases(39.1%) and 14 cases(30.4%), respectively. The differences of the gain of SPT to the fast phase and slow phase direction in the overall groups and light, medium and strong groups of SN intensity respectively were statistically significant(ttotal=13.338, tlight=6.184, tmedium=8.436, tstrong=8.477, all of P<0.001). The difference of SPT gain in SN fast phase direction between groups with different SN intensity was statistically significant(F=9.639, P<0.001),there was no statistically significant difference in SPT gain between the groups on the SN slow phase direction(F=1.137, P=0.330).The SN intensity significantly negatively correlated with the SPT gain of the fast phase direction of SN (r=-0.433, P=0.003), that was, the SPT gain on the fast phase direction of SN decreased with the increase of SN intensity. There was no significant correlation between SN intensity and the gain of SPT on the slow phase direction of SN (r=-0.061, P=0.687). SPT waveform analysis showed that type I, type II and type III accounted for 8 cases(17.4%), 21 cases(45.6%) and 17 cases(37.0%), respectively. The corresponding mean values of SN intensity were (3.71±0.69)°/s, (7.44±1.88)°/s, (20.04±5.53)°/s, respectively, without type IV wave. The intensity of SN was positively correlated with the asymmetric value of the gain of SPT left and right(r=0.450,P=0.002). That was, with the increase of SN strength, the asymmetric value also increased, and the worse the asymmetry of the gain of SPT left and right pursuit was, the worse the SPT waveform was. Conclusion: SPT gain, asymmetry and SPT waveforms are all affected by SN, and the greater the intensity of SN, the greater the influence on the three. When SN is strong, type III waves may occur, suggesting that acute peripheral vestibular syndrome can also affect the visual ocularmotor systems.

Exploring the Moderation Effect of Educational Stage on Visual Magnocellular Functioning Linked to Reading: A Study in French Primary School Children.

Many studies have investigated the visual magnocellular system functioning in dyslexia. However, very little is known on the relationship between the visual magnocellular system functioning and reading abilities in typical developing readers. In this study, we aimed at studying this relationship and more specifically the moderation effect of educational stage on this link. We thus tested 82 French typical developing readers (40 beginning readers—Grade 1 and 42 advanced readers—Grade 5) with reading tests and a coherent dot motion task measuring the visual magnocellular functioning. Results indicate positive correlations between visual magnocellular functioning and reading for beginning readers but not for advanced readers. Moreover, moderation analyses confirm that reading proficiency moderates the relationship between magnocellular system functioning and reading outcomes. We concluded that the relationship between visual magnocellular pathway functioning and reading abilities in typical developing readers could depend on reading proficiency.

Retina-Inspired Organic Heterojunction-Based Optoelectronic Synapses for Artificial Visual Systems.

For the realization of retina-inspired neuromorphic visual systems which simulate basic functions of human visual systems, optoelectronic synapses capable of combining perceiving, processing, and memorizing in a single device have attracted immense interests. Here, optoelectronic synaptic transistors based on tris(2-phenylpyridine) iridium (Ir(ppy)3) and poly(3,3-didodecylquarterthiophene) (PQT-12) heterojunction structure are presented. The organic heterojunction serves as a basis for distinctive synaptic characteristics under different wavelengths of light. Furthermore, synaptic transistor arrays are fabricated to demonstrate their optical perception efficiency and color recognition capability under multiple illuminating conditions. The wavelength-tunability of synaptic behaviors further enables the mimicry of mood-modulated visual learning and memorizing processes of humans. More significantly, the computational dynamics of neurons of synaptic outputs including associated learning and optical logic functions can be successfully demonstrated on the presented devices. This work may locate the stage for future studies on optoelectronic synaptic devices toward the implementation of artificial visual systems.

Chronobiotic effect of melatonin in experimental optic neuritis

Optic neuritis (ON) is an inflammatory condition of the optic nerve, which leads to retinal ganglion cell (RGC) loss. A subset of RGCs expressing the photopigment melanopsin regulates non-image-forming visual system (NIFVS) functions such as pupillary light reflex (PLR) and circadian rhythms. Melatonin is a chronobiotic agent able to regulate the circadian system. We analyzed the effect of ON on the NIFVS, and the effect of melatonin on the NIFVS alterations induced by ON. For this purpose, optic nerves from male Wistar rats received vehicle or bacterial lipopolysaccharide (LPS), and one group of animals received a subcutaneous pellet of melatonin or a sham procedure. The NIFVS was analyzed in terms of: i) blue light-evoked PLR, ii) the communication between the retina and the suprachiasmatic nuclei (by anterograde transport, and ex vivo magnetic resonance images), iii) locomotor activity rhythm, and iv) Brn3a(+) and melanopsin(+) RGC number (by immunohistochemistry). Experimental ON significantly decreased the blue light-evoked PLR, induced a misconnection between the retina and the suprachiasmatic nuclei, decreased Brn3a(+) RGCs, but not melanopsin(+) RGC number. A bilateral injection of LPS significantly increased the light (but not dark) phase locomotor activity, rhythm periodicity, and time of offset activity. Melatonin prevented the decrease in blue light-evoked PLR, and locomotor activity rhythm alterations induced by ON. These results support that ON provoked alterations of the circadian physiology, and that melatonin could restore the circadian system misalignment.

Laying the foundation for an International Classification of Functioning, Disability and Health Core Set for community-dwelling elderly adults in primary care: the clinical perspective identified in a cross-sectional study

ObjectivesHaving more information about the biopsychosocial functioning of their geriatric patients might help physicians better balance medical interventions according to patients’ needs. For this reason, we aimed to develop an...

Auditory and Visual System White Matter Is Differentially Impacted by Normative Aging in Macaques.

Deficits in auditory and visual processing are commonly encountered by older individuals. In addition to the relatively well described age-associated pathologies that reduce sensory processing at the level of the cochlea and eye, multiple changes occur along the ascending auditory and visual pathways that further reduce sensory function in each domain. One fundamental question that remains to be directly addressed is whether the structure and function of the central auditory and visual systems follow similar trajectories across the lifespan or sustain the impacts of brain aging independently. The present study used diffusion magnetic resonance imaging and electrophysiological assessments of auditory and visual system function in adult and aged macaques to better understand how age-related changes in white matter connectivity at multiple levels of each sensory system might impact auditory and visual function. In particular, the fractional anisotropy (FA) of auditory and visual system thalamocortical and interhemispheric corticocortical connections was estimated using probabilistic tractography analyses. Sensory processing and sensory system FA were both reduced in older animals compared with younger adults. Corticocortical FA was significantly reduced only in white matter of the auditory system of aged monkeys, while thalamocortical FA was lower only in visual system white matter of the same animals. Importantly, these structural alterations were significantly associated with sensory function within each domain. Together, these results indicate that age-associated deficits in auditory and visual processing emerge in part from microstructural alterations to specific sensory white matter tracts, and not from general differences in white matter condition across the aging brain.SIGNIFICANCE STATEMENT Age-associated deficits in sensory processing arise from structural and functional alterations to both peripheral sensory organs and central brain regions. It remains unclear whether different sensory systems undergo similar or distinct trajectories in function across the lifespan. To provide novel insights into this question, this study combines electrophysiological assessments of auditory and visual function with diffusion MRI in aged macaques. The results suggest that age-related sensory processing deficits in part result from factors that impact the condition of specific white matter tracts, and not from general decreases in connectivity between sensory brain regions. Such anatomic specificity argues for a framework aimed at understanding vulnerabilities with relatively local influence and brain region specificity.

Comparing biological and artificial vision systems: Network measures of functional connectivity

Advances in Deep Convolutional Neural Networks (DCNN) provide new opportunities for computational neuroscience to pose novel questions regarding the function of biological visual systems. Some attempts have been made to utilize advances in machine learning to answer neuroscientific questions, but how to appropriately make comparisons between the biological systems and artificial neural network structure is an open question. This analysis quantifies network properties of the mouse visual system and a common DCNN model (VGG16), to determine if this comparison is appropriate. Utilizing weighted graph-theoretic measures of node density (weighted node-degree), path length, local clustering coefficient, and betweenness, differences in functional connectivity patterns in the modern artificial computer vision system and the biological vision system are quantified. Results show that the mouse exhibits network measure distributions more similar to Poisson than normal, whereas the VGG16 exhibits network measure distributions with a more Gaussian shape than the sampled biological network. The artificial network shows higher density measures and shorter path lengths in comparison to the biological network. These results show that training a VGG16 for an object recognition task is unlikely to produce a network whose functional connectivity is similar to the mammalian visual system.

Environmentally relevant concentrations of boscalid exposure affects the neurobehavioral response of zebrafish by disrupting visual and nervous systems

Boscalid is a persistent fungicide that is frequently detected in surface waters and may be neurotoxic to aquatic organisms. Herein, we evaluated the effects of environmentally relevant boscalid concentrations to zebrafish to explore its potentially neurotoxic mechanisms of effect. Behavioral responses (swimming, phototaxis, and predation), histopathology, transcriptomics, biochemical parameter analysis and gene expression of larval and adult zebrafish following boscalid treatment were assessed. We found that boscalid significantly inhibited the locomotor ability and phototactic response of larvae after an 8-d exposure, and altered the locomotor activity, predation trajectories and ability in adults after a 21-d exposure. It was noted that predation rates of zebrafish were significantly decreased by 30% and 100% after exposure to 0.1 and 1.0 mg/L boscalid, respectively. Adverse alterations in the cell differentiation of eyes and brain injury were also observed in both larvae and adults following boscalid exposure. The expression of genes related to neurodevelopment, neurotransmission, eye development, and visual function, in conjunction with RNA-Seq results, indicated that boscalid may impair visual phototransduction and nervous system processes in larval zebrafish. Conclusively, boscalid exposure may affect the neurobehavioral response of zebrafish by impairing proper visual and nervous system function.

80‐2: Spatiochromatic Model for Image‐Quality Prediction of High‐Dynamic‐Range and Wide‐Color‐Gamut Content

This paper presents an approach to predicting image quality by spatially filtering images before generating color difference maps with pixel‐based color difference metrics. The resulting difference maps can then be pooled across the whole image. This approach was originally developed for CIELAB color space under the name S‐CIELAB. We extend this approach to use the recently developed ICTCP color space to improve the prediction accuracy for high dynamic range and wide color gamut images. The filtering is based on the chromatic and achromatic contrast sensitivity function of the human visual system. Our results on four existing subjective image quality databases containing high dynamic range and wide color gamut images show substantial improvements at low computational cost, outperforming existing color difference metrics.

The Influence of Object-Color Knowledge on Emerging Object Representations in the Brain.

The ability to rapidly and accurately recognize complex objects is a crucial function of the human visual system. To recognize an object, we need to bind incoming visual features, such as color and form, together into cohesive neural representations and integrate these with our preexisting knowledge about the world. For some objects, typical color is a central feature for recognition; for example, a banana is typically yellow. Here, we applied multivariate pattern analysis on time-resolved neuroimaging (MEG) data to examine how object-color knowledge affects emerging object representations over time. Our results from 20 participants (11 female) show that the typicality of object-color combinations influences object representations, although not at the initial stages of object and color processing. We find evidence that color decoding peaks later for atypical object-color combinations compared with typical object-color combinations, illustrating the interplay between processing incoming object features and stored object knowledge. Together, these results provide new insights into the integration of incoming visual information with existing conceptual object knowledge.SIGNIFICANCE STATEMENT To recognize objects, we have to be able to bind object features, such as color and shape, into one coherent representation and compare it with stored object knowledge. The MEG data presented here provide novel insights about the integration of incoming visual information with our knowledge about the world. Using color as a model to understand the interaction between seeing and knowing, we show that there is a unique pattern of brain activity for congruently colored objects (e.g., a yellow banana) relative to incongruently colored objects (e.g., a red banana). This effect of object-color knowledge only occurs after single object features are processed, demonstrating that conceptual knowledge is accessed relatively late in the visual processing hierarchy.

Successful visually guided eye movements following sight restoration after congenital cataracts.

Sensitive periods have previously been identified for several human visual system functions. Yet, it is unknown to what degree the development of visually guided oculomotor control depends on early visual experience—for example, whether and to what degree humans whose sight was restored after a transient period of congenital visual deprivation are able to conduct visually guided eye movements. In the present study, we developed new calibration and analysis techniques for eye tracking data contaminated with pervasive nystagmus, which is typical for this population. We investigated visually guided eye movements in sight recovery individuals with long periods of visual pattern deprivation (3–36 years) following birth due to congenital, dense, total, bilateral cataracts. As controls we assessed (1) individuals with nystagmus due to causes other than cataracts, (2) individuals with developmental cataracts after cataract removal, and (3) individuals with normal vision. Congenital cataract reversal individuals were able to perform visually guided gaze shifts, even when their blindness had lasted for decades. The typical extensive nystagmus of this group distorted eye movement trajectories, but measures of latency and accuracy were as expected from their prevailing nystagmus—that is, not worse than in the nystagmus control group. To the best of our knowledge, the present quantitative study is the first to investigate the characteristics of oculomotor control in congenital cataract reversal individuals, and it indicates a remarkable effectiveness of visually guided eye movements despite long-lasting periods of visual deprivation.

A Tactile-based Brain Computer Interface P300 Paradigm Using Vibration Frequency and Spatial Location

Visual based brain-computer interface (BCI) has been widely investigated for the severely disabled patients. However, this modality is not applicable to the persons who have lost their visual function. This study aims to develop an alternative BCI using tactile stimuli only. An event-related potential (ERP) based BCI applying vibrotactile stimuli was proposed. It featured a combination of frequency and spatial information as a cue for binary choices. Two identical mechanical vibrotactile tactors were tied to each index finger of the two hands of a subject, to provide vibrotactile stimuli at various frequencies and constitute a three-stimulus oddball paradigm with one attended stimulus, one ignored stimulus and one disturbance stimulus. Ten healthy subjects participated in the experiments, and the classification of P300 signals was conducted by a stepwise linear discriminate analysis algorithm. Significant P300 components were evoked at approximately 360 ms after the onset of the target stimuli for each subject, and an average classification accuracy of 79% was achieved. This work demonstrates the feasibility of employing vibrotactile stimuli to build an ERP based BCI. The patients without a functional visual system could benefit from the presented paradigm.

Crowding in humans is unlike that in convolutional neural networks

Object recognition is a primary function of the human visual system. It has recently been claimed that the highly successful ability to recognise objects in a set of emergent computer vision systems—Deep Convolutional Neural Networks (DCNNs)—can form a useful guide to recognition in humans. To test this assertion, we systematically evaluated visual crowding, a dramatic breakdown of recognition in clutter, in DCNNs and compared their performance to extant research in humans. We examined crowding in three architectures of DCNNs with the same methodology as that used among humans. We manipulated multiple stimulus factors including inter-letter spacing, letter colour, size, and flanker location to assess the extent and shape of crowding in DCNNs. We found that crowding followed a predictable pattern across architectures that was different from that in humans. Some characteristic hallmarks of human crowding, such as invariance to size, the effect of target-flanker similarity, and confusions between target and flanker identities, were completely missing, minimised or even reversed. These data show that DCNNs, while proficient in object recognition, likely achieve this competence through a set of mechanisms that are distinct from those in humans. They are not necessarily equivalent models of human or primate object recognition and caution must be exercised when inferring mechanisms derived from their operation.

Auditory Processing Deficits Are Selectively Associated with Medial Temporal Lobe Mnemonic Function and White Matter Integrity in Aging Macaques.

Deficits in auditory function and cognition are hallmarks of normative aging. Recent evidence suggests that hearing-impaired individuals have greater risks of developing cognitive impairment and dementia compared to people with intact auditory function, although the neurobiological bases underlying these associations are poorly understood. Here, a colony of aging macaques completed a battery of behavioral tests designed to probe frontal and temporal lobe-dependent cognition. Auditory brainstem responses (ABRs) and visual evoked potentials were measured to assess auditory and visual system function. Structural and diffusion magnetic resonance imaging were then performed to evaluate the microstructural condition of multiple white matter tracts associated with cognition. Animals showing higher cognitive function had significantly better auditory processing capacities, and these associations were selectively observed with tasks that primarily depend on temporal lobe brain structures. Tractography analyses revealed that the fractional anisotropy (FA) of the fimbria-fornix and hippocampal commissure were associated with temporal lobe-dependent visual discrimination performance and auditory sensory function. Conversely, FA of frontal cortex-associated white matter was not associated with auditory processing. Visual sensory function was not associated with frontal or temporal lobe FA, nor with behavior. This study demonstrates significant and selective relationships between ABRs, white matter connectivity, and higher-order cognitive ability.

Axonal precursor miRNAs hitchhike on endosomes and locally regulate the development of neural circuits

Various species of non‐coding RNAs (ncRNAs) are enriched in specific subcellular compartments, but the mechanisms orchestrating their localization and their local functions remain largely unknown. We investigated both aspects using the elongating retinal ganglion cell axon and its tip, the growth cone, as models. We reveal that specific endogenous precursor microRNAs (pre‐miRNAs) are actively trafficked to distal axons by hitchhiking primarily on late endosomes/lysosomes. Upon exposure to the axon guidance cue semaphorin 3A (Sema3A), pre‐miRNAs are processed specifically within axons into newly generated miRNAs, one of which, in turn, silences the basal translation of tubulin beta 3 class III (TUBB3), but not amyloid beta precursor protein (APP). At the organismal level, these mature miRNAs are required for growth cone steering and a fully functional visual system. Overall, our results uncover a novel mode of ncRNA transport from one cytosolic compartment to another within polarized cells. They also reveal that newly generated miRNAs are critical components of a ncRNA‐based signaling pathway that transduces environmental signals into the structural remodeling of subcellular compartments.

17β-Estradiol Delivered in Eye Drops: Evidence of Impact on Protein Networks and Associated Biological Processes in the Rat Retina through Quantitative Proteomics.

To facilitate the development of broad-spectrum retina neuroprotectants that can be delivered through topical dosage forms, this proteomics study focused on analyzing target engagements through the identification of functional protein networks impacted after delivery of 17β-estradiol in eye drops. Specifically, the retinae of ovariectomized Brown Norway rats treated with daily eye drops of 17β-estradiol for three weeks were compared to those of vehicle-treated ovariectomized control animals. We searched the acquired raw data against a composite protein sequence database by using Mascot, as well as employed label-free quantification to detect changes in protein abundances. Our investigation using rigorous validation criteria revealed 331 estrogen-regulated proteins in the rat retina (158 were up-regulated, while 173 were down-regulated by 17β-estradiol delivered in eye drops). Comprehensive pathway analyses indicate that these proteins are relevant overall to nervous system development and function, tissue development, organ development, as well as visual system development and function. We also present 18 protein networks with associated canonical pathways showing the effects of treatments for the detailed analyses of target engagements regarding potential application of estrogens as topically delivered broad-spectrum retina neuroprotectants. Profound impact on crystallins is discussed as one of the plausible neuroprotective mechanisms.

The internal noise of the visual system and cognitive functions in schizophrenia

Abstract In this study, we report the existence of correlation between the ability of the object perception in the presence of the external noise and the cognitive functioning in schizophrenia. The level of the internal noise of the visual system have been measured for the 41 healthy volunteers and for the 68 schizophrenia patients in the task of distinguishing the location of the rupture of the Landolt ring, under the conditions of external interference. The collected evidence demonstrated an increase in the level of internal noise of the visual system in the patients with schizophrenia.