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1.
Parasitol Res ; 118(9): 2531-2541, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31286263

RESUMO

Visual performance and environmental conditions can influence both behavioral patterns and predator-prey interactions of fish. Eye parasites can impair their host's sensory performance with important consequences for the detection of prey, predators, and conspecifics. We used European perch (Perca fluviatilis) experimentally infected with the eye fluke Tylodelphys clavata and evaluated their feeding behavior and competitive ability under competition with non-infected conspecifics, in groups of four individuals, for two different prey species (Asellus aquaticus and Daphnia magna). To test whether the effect of T. clavata infection differs at different light conditions, we performed the experiments at two light intensities (600 and 6 lx). Foraging efficiency of perch was significantly affected by infection but not by light intensity. The distance at which infected fish attacked both prey species was significantly shorter in comparison to non-infected conspecifics. Additionally, infected fish more often unsuccessfully attacked A. aquaticus. Although the outcome of competition depended on prey species, there was a general tendency that non-infected fish consumed more of the available prey under both light intensities. Even though individual prey preferences for either A. aquaticus or D. magna were observed, we could not detect that infected fish change their prey preference to compensate for a reduced competitive foraging ability. As infection of T. clavata impairs foraging efficiency and competitive ability, infected fish would need to spend more time foraging to attain similar food intake as non-infected conspecifics; this presumably increases predation risk and potentially enhances transmission success to the final host.


Assuntos
Comportamento Alimentar/fisiologia , Percas/parasitologia , Comportamento Predatório/fisiologia , Trematódeos/patogenicidade , Visão Ocular/fisiologia , Animais , Oftalmopatias/parasitologia , Oftalmopatias/veterinária , Interações Hospedeiro-Parasita/fisiologia
2.
Neuron ; 103(4): 658-672.e6, 2019 08 21.
Artigo em Inglês | MEDLINE | ID: mdl-31227309

RESUMO

The functions of the diverse retinal ganglion cell types in primates and the parallel visual pathways they initiate remain poorly understood. Here, unusual physiological and computational properties of the ON and OFF smooth monostratified ganglion cells are explored. Large-scale multi-electrode recordings from 48 macaque retinas revealed that these cells exhibit irregular receptive field structure composed of spatially segregated hotspots, quite different from the classic center-surround model of retinal receptive fields. Surprisingly, visual stimulation of different hotspots in the same cell produced spikes with subtly different spatiotemporal voltage signatures, consistent with a dendritic contribution to hotspot structure. Targeted visual stimulation and computational inference demonstrated strong nonlinear subunit properties associated with each hotspot, supporting a model in which the hotspots apply nonlinearities at a larger spatial scale than bipolar cells. These findings reveal a previously unreported nonlinear mechanism in the output of the primate retina that contributes to signaling spatial information.


Assuntos
Células Ganglionares da Retina/classificação , Potenciais de Ação , Animais , Contagem de Células , Eletrofisiologia/métodos , Macaca fascicularis , Macaca mulatta , Modelos Neurológicos , Dinâmica não Linear , Técnicas de Patch-Clamp , Estimulação Luminosa , Células Ganglionares da Retina/fisiologia , Células Ganglionares da Retina/efeitos da radiação , Visão Ocular/fisiologia
3.
Doc Ophthalmol ; 139(2): 161-168, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31161576

RESUMO

PURPOSE: It is desirable to make VEP-based acuity estimates match standard subjective acuity numerically, as the latter is familiar to ophthalmologists and optometrists. This is achieved by applying an empirical conversion factor, and previous studies found the resulting values to be within ±1 octave of subjective acuity. This leaves room for improvement. In the present study, we tested for the case of a monocular acuity deficit whether the known difference between subjective and objective acuity in the trusted fellow eye can be used to get a more precise objective estimate in the eye of which the acuity is to be estimated. In other words, we tested whether it would make sense to determine a patient-specific conversion factor. METHODS: In 19 subjects, we obtained monocular objective and subjective acuity estimates with both eyes. Normal vision and artificially degraded vision were tested. Subjective acuity was taken as the veridical value. We computed the differences between objective and subjective acuity and reasoned that if these were correlated between eyes and acuity levels, the valid information from the trusted healthy eye could be used to improve the precision of the acuity estimate in the other, potentially impaired, eye. RESULTS: The difference between objective and subjective acuity values was neither correlated significantly between eyes, nor was it correlated significantly between acuity levels. CONCLUSIONS: Knowledge about the discrepancy between objective and subjective acuity values in one eye does not help improving the accuracy of acuity estimates in the other eye. The lack of a significant correlation between eyes even at the same acuity level suggests that a major part of the discrepancies between subjective acuity and VEP-based acuity is not the result of factors that would equally apply to both eyes, such as cortical morphology.


Assuntos
Potenciais Evocados Visuais/fisiologia , Lateralidade Funcional/fisiologia , Acuidade Visual/fisiologia , Adolescente , Adulto , Eletrorretinografia , Feminino , Humanos , Masculino , Visão Ocular/fisiologia , Adulto Jovem
4.
Nat Commun ; 10(1): 2431, 2019 06 03.
Artigo em Inglês | MEDLINE | ID: mdl-31160566

RESUMO

Contextual modulation of neuronal responses by surrounding environments is a fundamental attribute of sensory processing. In the mammalian retina, responses of On-Off direction selective ganglion cells (DSGCs) are modulated by motion contexts. However, the underlying mechanisms are unknown. Here, we show that posterior-preferring DSGCs (pDSGCs) are sensitive to discontinuities of moving contours owing to contextually modulated cholinergic excitation from starburst amacrine cells (SACs). Using a combination of synapse-specific genetic manipulations, patch clamp electrophysiology and connectomic analysis, we identified distinct circuit motifs upstream of On and Off SACs that are required for the contextual modulation of pDSGC activity for bright and dark contrasts. Furthermore, our results reveal a class of wide-field amacrine cells (WACs) with straight, unbranching dendrites that function as "continuity detectors" of moving contours. Therefore, divergent circuit motifs in the On and Off pathways extend the information encoding of On-Off DSGCs beyond their direction selectivity during complex stimuli.


Assuntos
Acetilcolina/metabolismo , Células Amácrinas/metabolismo , Percepção de Movimento/fisiologia , Células Ganglionares da Retina/metabolismo , Sinapses/metabolismo , Visão Ocular/fisiologia , Ácido gama-Aminobutírico/metabolismo , Células Amácrinas/fisiologia , Animais , Conectoma , Dendritos/metabolismo , Ácido Glutâmico/metabolismo , Camundongos , Técnicas de Patch-Clamp , Receptores de GABA-A/genética , Células Ganglionares da Retina/fisiologia , Percepção Visual/fisiologia
5.
Sensors (Basel) ; 19(12)2019 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-31226796

RESUMO

The development of computer vision based systems dedicated to help visually impaired people to perceive the environment, to orientate and navigate has been the main research subject of many works in the recent years. A significant ensemble of resources has been employed to support the development of sensory substitution devices (SSDs) and electronic travel aids for the rehabilitation of the visually impaired. The Sound of Vision (SoV) project used a comprehensive approach to develop such an SSD, tackling all the challenging aspects that so far restrained the large scale adoption of such systems by the intended audience: Wearability, real-time operation, pervasiveness, usability, cost. This article is set to present the artificial vision based component of the SoV SSD that performs the scene reconstruction and segmentation in outdoor environments. In contrast with the indoor use case, where the system acquires depth input from a structured light camera, in outdoors SoV relies on stereo vision to detect the elements of interest and provide an audio and/or haptic representation of the environment to the user. Our stereo-based method is designed to work with wearable acquisition devices and still provide a real-time, reliable description of the scene in the context of unreliable depth input from the stereo correspondence and of the complex 6 DOF motion of the head-worn camera. We quantitatively evaluate our approach on a custom benchmarking dataset acquired with SoV cameras and provide the highlights of the usability evaluation with visually impaired users.


Assuntos
Inteligência Artificial , Auxiliares Sensoriais , Visão Ocular/fisiologia , Pessoas com Deficiência Visual , Humanos , Orientação/fisiologia , Interface Usuário-Computador , Dispositivos Eletrônicos Vestíveis
6.
J Headache Pain ; 20(1): 64, 2019 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-31146673

RESUMO

BACKGROUND: Migraine aura (MA) is a common and disabling neurological condition, characterized by transient visual, and less frequently sensory and dysphasic aura disturbances. MA is associated with an increased risk of cardiovascular disorders and is often clinically difficult to distinguish from other serious neurological disorders such as transient ischemic attacks and epilepsy. Optimal clinical classification of MA symptoms is important for more accurate diagnosis and improved understanding of the pathophysiology of MA through clinical studies. MAIN BODY: A systematic review of previous prospective and retrospective systematic recordings of visual aura symptoms (VASs) was performed to provide an overview of the different types of visual phenomena occurring during MA and their respective frequencies in patients. We found 11 retrospective studies and three prospective studies systematically describing VASs. The number of different types of VASs reported by patients in the studies ranged from two to 23. The most common were flashes of bright light, "foggy" vision, zigzag lines, scotoma, small bright dots and 'like looking through heat waves or water'. CONCLUSIONS: We created a comprehensive list of VAS types reported by migraine patients based on all currently available data from clinical studies, which can be used for testing and validation in future studies. We propose that, based on this work, an official list of VAS types should be developed, preferably within the context of the International Classification of Headache Disorders of the International Headache Society.


Assuntos
Enxaqueca com Aura/diagnóstico , Enxaqueca com Aura/fisiopatologia , Visão Ocular/fisiologia , Adulto , Epilepsia/diagnóstico , Epilepsia/epidemiologia , Epilepsia/fisiopatologia , Feminino , Alucinações/diagnóstico , Alucinações/epidemiologia , Alucinações/fisiopatologia , Humanos , Ataque Isquêmico Transitório/diagnóstico , Ataque Isquêmico Transitório/epidemiologia , Ataque Isquêmico Transitório/fisiopatologia , Masculino , Enxaqueca com Aura/epidemiologia , Estudos Prospectivos , Estudos Retrospectivos
7.
Opt Express ; 27(7): 9343-9360, 2019 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-31045087

RESUMO

A 3D light field display typically reconstructs a 3D scene by sampling either the projections of the 3D scene at different depths or the directions of the light rays apparently emitted by the 3D scene and viewed from different eye positions. These light field display methods are potentially capable of rendering correct or nearly correct focus cues and therefore addressing the well-known vergence-accommodation conflict problem plaguing the conventional stereoscopic displays. However, very limited efforts have been made to investigate the effects of light ray sampling on the quality of the rendered focus cues and thus the visual responses of a viewer in light field displays. In this paper, by accounting for both the specifications of a light field display system and the ocular factors of the human visual system, we systematically model and analyze the ray position sampling issue in the reconstruction of the light field and characterize its effect on the quality of the rendered retinal image and on the accommodative response in viewing a 3D light field display. Using a recently developed 3D light field display prototype, we further experimentally validated the effects of ray position sampling on the resolution and accommodative response of a light field display, of which the result matches with theoretical characterization.


Assuntos
Imagem Tridimensional/métodos , Luz , Retina/efeitos da radiação , Visão Ocular/fisiologia , Acomodação Ocular/fisiologia , Percepção de Profundidade/fisiologia , Humanos , Modelos Teóricos
8.
Sensors (Basel) ; 19(10)2019 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-31091679

RESUMO

Vibrations often cause visual fatigue for drivers, and measuring the relative motion between the driver and the display is important for evaluating this visual fatigue. This paper proposes a non-contact videometric measurement method for studying the three-dimensional trajectories of the driver's eyes based on stereo vision. The feasibility of this method is demonstrated by dynamic calibration. A high-speed dual-camera image acquisition system is used to obtain high-definition images of the face, and the relative trajectories between the eyes and the display are obtained by a set of robust algorithms. The trajectories of the eyes in three-dimensional space are then reconstructed during the vehicle driving process. This new approach provides three-dimensional information and is effective for assessing how vibration affects human visual performance.


Assuntos
Atenção/fisiologia , Condução de Veículo , Movimentos Oculares/fisiologia , Visão Ocular/fisiologia , Acidentes de Trânsito , Algoritmos , Humanos , Fenômenos Fisiológicos Oculares
9.
PLoS Comput Biol ; 15(5): e1007063, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-31125331

RESUMO

Visual performance depends on polar angle, even when eccentricity is held constant; on many psychophysical tasks observers perform best when stimuli are presented on the horizontal meridian, worst on the upper vertical, and intermediate on the lower vertical meridian. This variation in performance 'around' the visual field can be as pronounced as that of doubling the stimulus eccentricity. The causes of these asymmetries in performance are largely unknown. Some factors in the eye, e.g. cone density, are positively correlated with the reported variations in visual performance with polar angle. However, the question remains whether these correlations can quantitatively explain the perceptual differences observed 'around' the visual field. To investigate the extent to which the earliest stages of vision-optical quality and cone density-contribute to performance differences with polar angle, we created a computational observer model. The model uses the open-source software package ISETBIO to simulate an orientation discrimination task for which visual performance differs with polar angle. The model starts from the photons emitted by a display, which pass through simulated human optics with fixational eye movements, followed by cone isomerizations in the retina. Finally, we classify stimulus orientation using a support vector machine to learn a linear classifier on the photon absorptions. To account for the 30% increase in contrast thresholds for upper vertical compared to horizontal meridian, as observed psychophysically on the same task, our computational observer model would require either an increase of ~7 diopters of defocus or a reduction of 500% in cone density. These values far exceed the actual variations as a function of polar angle observed in human eyes. Therefore, we conclude that these factors in the eye only account for a small fraction of differences in visual performance with polar angle. Substantial additional asymmetries must arise in later retinal and/or cortical processing.


Assuntos
Modelos Neurológicos , Modelos Psicológicos , Campos Visuais/fisiologia , Algoritmos , Biologia Computacional , Movimentos Oculares/fisiologia , Humanos , Fenômenos Fisiológicos Oculares , Orientação/fisiologia , Estimulação Luminosa , Psicofísica , Células Fotorreceptoras Retinianas Cones/fisiologia , Software , Máquina de Vetores de Suporte , Visão Ocular/fisiologia
10.
Nat Commun ; 10(1): 2274, 2019 05 22.
Artigo em Inglês | MEDLINE | ID: mdl-31118424

RESUMO

Detection and discrimination of spatial patterns is thought to originate with photoreception by rods and cones. Here, we investigated whether the inner-retinal photoreceptor melanopsin could represent a third origin for form vision. We developed a 4-primary visual display capable of presenting patterns differing in contrast for melanopsin vs cones, and generated spectrally distinct stimuli that were indistinguishable for cones (metamers) but presented contrast for melanopsin. Healthy observers could detect sinusoidal gratings formed by these metamers when presented in the peripheral retina at low spatial (≤0.8 cpd) and temporal (≤0.45 Hz) frequencies, and Michelson contrasts ≥14% for melanopsin. Metameric gratings became invisible at lower light levels (<1013 melanopsin photons cm-2 sr-1 s-1) when rods are more active. The addition of metameric increases in melanopsin contrast altered appearance of greyscale representations of coarse gratings and a range of everyday images. These data identify melanopsin as a new potential origin for aspects of spatial vision in humans.


Assuntos
Percepção de Forma/fisiologia , Opsinas de Bastonetes/fisiologia , Visão Ocular/fisiologia , Feminino , Voluntários Saudáveis , Humanos , Masculino , Células Fotorreceptoras Retinianas Cones/fisiologia
12.
Invest Ophthalmol Vis Sci ; 60(5): 1538-1546, 2019 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-30994864

RESUMO

Purpose: Recent evidence suggests that retinal photoreceptor cells have an important role in the pathogenesis of retinal microvascular lesions in diabetes. We investigated the role of rod cell phototransduction on the pathogenesis of early diabetic retinopathy (DR) using Gnat1-/- mice (which causes permanent inhibition of phototransduction in rod cells without degeneration). Methods: Retinal thickness, oxidative stress, expression of inflammatory proteins, electroretinograms (ERG) and optokinetic responses, and capillary permeability and degeneration were evaluated at up to 8 months of diabetes. Results: The diabetes-induced degeneration of retinal capillaries was significantly inhibited in the Gnat1-/- diabetics. The effect of the Gnat1 deletion on the diabetes-induced increase in permeability showed a nonuniform accumulation of albumin in the neural retina; the defect was inhibited in diabetic Gnat1-/- mice in the inner plexiform layer (IPL), but neither in the outer plexiform (OPL) nor inner nuclear (INL) layers. In Gnat1-deficient animals, the diabetes-induced increase in expression of inflammatory associated proteins (iNOS and ICAM-1, and phosphorylation of IĸB) in the retina, and the leukocyte mediated killing of retinal endothelial cells were inhibited, however the diabetes-mediated induction of oxidative stress was not inhibited. Conclusions: In conclusion, deletion of transducin1 (and the resulting inhibition of phototransduction in rod cells) inhibits the development of retinal vascular pathology in early DR.


Assuntos
Diabetes Mellitus Experimental/fisiopatologia , Retinopatia Diabética/etiologia , Retinopatia Diabética/fisiopatologia , Subunidades alfa de Proteínas de Ligação ao GTP/genética , Deleção de Genes , Células Fotorreceptoras Retinianas Bastonetes/fisiologia , Transducina/genética , Visão Ocular/fisiologia , Animais , Permeabilidade Capilar , Retinopatia Diabética/metabolismo , Eletrorretinografia , Proteínas I-kappa B/metabolismo , Immunoblotting , Molécula 1 de Adesão Intercelular/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Mutantes , Óxido Nítrico Sintase Tipo II/metabolismo , Nistagmo Optocinético/fisiologia , Estresse Oxidativo , Fosforilação , Vasos Retinianos/patologia , Estreptozocina , Tomografia de Coerência Óptica
13.
J Vis ; 19(4): 3, 2019 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-30943529

RESUMO

Research on functional changes across the adult lifespan has been dominated by studies related to cognitive processes. However, it has become evident that a more comprehensive approach to behavioral aging is needed. In particular, our understanding of age-related perceptual changes is limited. Visual motion perception is one of the most studied areas in perceptual aging and therefore, provides an excellent domain on the basis of which we can investigate the complexity of the aging process. We review the existing literature on how aging affects motion perception, including different processing stages, and consider links to cognitive and motor changes. We address the heterogeneity of results and emphasize the role of individual differences. Findings on age-related changes in motion perception ultimately illustrate the complexity of functional dynamics that can contribute to decline as well as stability during healthy aging. We thus propose that motion perception offers a conceptual framework for perceptual aging, encouraging a deliberate consideration of functional limits and resources emerging across the lifespan.


Assuntos
Envelhecimento/fisiologia , Percepção de Movimento/fisiologia , Feminino , Humanos , Masculino , Visão Ocular/fisiologia , Córtex Visual/fisiologia
14.
Nat Commun ; 10(1): 1162, 2019 03 11.
Artigo em Inglês | MEDLINE | ID: mdl-30858374

RESUMO

Divergent populations across different environments are exposed to critical sensory information related to locating a host or mate, as well as avoiding predators and pathogens. These sensory signals generate evolutionary changes in neuroanatomy and behavior; however, few studies have investigated patterns of neural architecture that occur between sensory systems, or that occur within large groups of closely-related organisms. Here we examine 62 species within the genus Drosophila and describe an inverse resource allocation between vision and olfaction, which we consistently observe at the periphery, within the brain, as well as during larval development. This sensory variation was noted across the entire genus and appears to represent repeated, independent evolutionary events, where one sensory modality is consistently selected for at the expense of the other. Moreover, we provide evidence of a developmental genetic constraint through the sharing of a single larval structure, the eye-antennal imaginal disc. In addition, we examine the ecological implications of visual or olfactory bias, including the potential impact on host-navigation and courtship.


Assuntos
Encéfalo/fisiologia , Drosophila/fisiologia , Comportamento Sexual Animal/fisiologia , Olfato/fisiologia , Visão Ocular/fisiologia , Animais , Animais Geneticamente Modificados , Evolução Biológica , Feminino , Discos Imaginais/crescimento & desenvolvimento , Larva/crescimento & desenvolvimento , Masculino , Filogenia , Navegação Espacial/fisiologia
15.
Sensors (Basel) ; 19(5)2019 Feb 27.
Artigo em Inglês | MEDLINE | ID: mdl-30818796

RESUMO

Although widely used in many applications, accurate and efficient human action recognition remains a challenging area of research in the field of computer vision. Most recent surveys have focused on narrow problems such as human action recognition methods using depth data, 3D-skeleton data, still image data, spatiotemporal interest point-based methods, and human walking motion recognition. However, there has been no systematic survey of human action recognition. To this end, we present a thorough review of human action recognition methods and provide a comprehensive overview of recent approaches in human action recognition research, including progress in hand-designed action features in RGB and depth data, current deep learning-based action feature representation methods, advances in human⁻object interaction recognition methods, and the current prominent research topic of action detection methods. Finally, we present several analysis recommendations for researchers. This survey paper provides an essential reference for those interested in further research on human action recognition.


Assuntos
Reconhecimento Automatizado de Padrão/métodos , Visão Ocular/fisiologia , Percepção Visual/fisiologia , Algoritmos , Atividades Humanas , Humanos , Movimento (Física) , Esqueleto/fisiologia , Inquéritos e Questionários
16.
Gait Posture ; 70: 284-288, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30925352

RESUMO

BACKGROUND: Obstacle crossing requires sufficient toe clearance for trip and fall prevention for which postural stability is a prerequisite. It is thought that the upper visual field plays an important role in the maintenance of postural stability, but its influence and age-dependence have not been investigated yet. RESEARCH QUESTION: What is the role of the visual fields in maintaining postural stability during crossing an obstacle in young and older adults?. METHODS: This study included 14 young adults and 14 older adults. The participants, wearing an accelerometer and liquid crystal shutter goggles, were asked to cross an obstacle under the following three conditions (i) full vision; (ii) total visual field occlusion at two steps before the obstacle, and (iii) lower visual field occlusion at two steps before the obstacle. The root mean square ratio in the mediolateral direction (RMSRML) for the three sections (i.e., approach to the obstacle, lead limb crossing, and trail limb crossing), as well as the root mean square in the mediolateral direction (RMSML) for each section were calculated. RESULTS: RMSML during lead limb crossing was significantly increased in older adults compared to young adults (p < 0.01). There was no significant main effect of visual condition and age group on RMSRML for the three steps. SIGNIFICANCE: The study results suggest postural lateral instability in older adults with poor balance ability during lead limb crossing. Regardless of age, the peripheral visual information appears to contribute minimally to the maintenance of postural lateral stability at least from two steps before the obstacle, when the participants perceived the surrounding environment and the size of the obstacle while approaching it.


Assuntos
Envelhecimento/fisiologia , Locomoção/fisiologia , Equilíbrio Postural/fisiologia , Visão Ocular/fisiologia , Campos Visuais/fisiologia , Acidentes por Quedas , Fatores Etários , Idoso , Fenômenos Biomecânicos , Feminino , Marcha/fisiologia , Humanos , Masculino , Adulto Jovem
17.
J Vis ; 19(3): 17, 2019 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-30924845

RESUMO

We used a letter transposition (LT) technique to investigate letter position coding during reading in central and peripheral vision. Eighteen subjects read aloud sentences in a rapid serial visual presentation task. The tests contained a baseline and three LT conditions with initial, internal, and final transpositions (e.g., "reading" to "erading", "raeding", and "readign"). The four reading conditions were tested in separate blocks. We found that LT had a smaller cost on peripheral (10° lower field) than on central reading speed, possibly due to the higher intrinsic position uncertainty of letters in the periphery. The pattern of cost (initial > final > internal) was the same for central and peripheral vision, indicating a similar lexical route for both. In the periphery, LT only affected transposed words, while in central vision it also affected untransposed words. This spread of the LT effect in central vision could not be accounted for by increased attention or memory load, or by decreased sentence context.


Assuntos
Leitura , Visão Ocular/fisiologia , Adolescente , Adulto , Atenção/fisiologia , Dislexia/fisiopatologia , Humanos , Linguagem , Memória/fisiologia , Reconhecimento Visual de Modelos/fisiologia , Incerteza , Percepção Visual , Adulto Jovem
18.
J Vis ; 19(3): 1, 2019 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-30821809

RESUMO

Bottom-up and top-down as well as low-level and high-level factors influence where we fixate when viewing natural scenes. However, the importance of each of these factors and how they interact remains a matter of debate. Here, we disentangle these factors by analyzing their influence over time. For this purpose, we develop a saliency model that is based on the internal representation of a recent early spatial vision model to measure the low-level, bottom-up factor. To measure the influence of high-level, bottom-up features, we use a recent deep neural network-based saliency model. To account for top-down influences, we evaluate the models on two large data sets with different tasks: first, a memorization task and, second, a search task. Our results lend support to a separation of visual scene exploration into three phases: the first saccade, an initial guided exploration characterized by a gradual broadening of the fixation density, and a steady state that is reached after roughly 10 fixations. Saccade-target selection during the initial exploration and in the steady state is related to similar areas of interest, which are better predicted when including high-level features. In the search data set, fixation locations are determined predominantly by top-down processes. In contrast, the first fixation follows a different fixation density and contains a strong central fixation bias. Nonetheless, first fixations are guided strongly by image properties, and as early as 200 ms after image onset, fixations are better predicted by high-level information. We conclude that any low-level, bottom-up factors are mainly limited to the generation of the first saccade. All saccades are better explained when high-level features are considered, and later, this high-level, bottom-up control can be overruled by top-down influences.


Assuntos
Movimentos Oculares/fisiologia , Fixação Ocular/fisiologia , Medições dos Movimentos Oculares , Feminino , Humanos , Masculino , Memória/fisiologia , Redes Neurais (Computação) , Estimulação Luminosa , Movimentos Sacádicos/fisiologia , Visão Ocular/fisiologia , Adulto Jovem
19.
Atten Percept Psychophys ; 81(5): 1589-1608, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30864108

RESUMO

The human visual system has an extraordinary capacity to compute three-dimensional (3D) shape structure for both geometrically regular and irregular objects. The goal of this study was to shed new light on the underlying representational structures that support this ability. Observers (N = 85) completed two complementary perceptual tasks. Experiment 1 involved whole-part matching of image parts to whole geometrically regular and irregular novel object shapes. Image parts comprised either regions of edge contour, volumetric parts, or surfaces. Performance was better for irregular than for regular objects and interacted with part type: volumes yielded better matching performance than surfaces for regular but not for irregular objects. The basis for this effect was further explored in Experiment 2, which used implicit part-whole repetition priming. Here, we orthogonally manipulated shape regularity and a new factor of surface diagnosticity (how predictive a single surface is of object identity). The results showed that surface diagnosticity, not object shape regularity, determined the differential processing of volumes and surfaces. Regardless of shape regularity, objects with low surface diagnosticity were better primed by volumes than by surfaces. In contrast, objects with high surface diagnosticity showed the opposite pattern. These findings are the first to show that surface diagnosticity plays a fundamental role in object recognition. We propose that surface-based shape primitives-rather than volumetric parts-underlie the derivation of 3D object shape in human vision.


Assuntos
Percepção de Forma/fisiologia , Reconhecimento Visual de Modelos/fisiologia , Priming de Repetição/fisiologia , Visão Ocular/fisiologia , Adulto , Feminino , Humanos , Masculino , Análise e Desempenho de Tarefas
20.
PLoS Biol ; 17(3): e3000144, 2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30835720

RESUMO

Every instant of perception depends on a cascade of brain processes calibrated to the history of sensory and decisional events. In the present work, we show that human visual perception is constantly shaped by two contrasting forces exerted by sensory adaptation and past decisions. In a series of experiments, we used multilevel modeling and cross-validation approaches to investigate the impact of previous stimuli and decisions on behavioral reports during adjustment and forced-choice tasks. Our results revealed that each perceptual report is permeated by opposite biases from a hierarchy of serially dependent processes: Low-level adaptation repels perception away from previous stimuli, whereas decisional traces attract perceptual reports toward the recent past. In this hierarchy of serial dependence, "continuity fields" arise from the inertia of decisional templates and not from low-level sensory processes. This finding is consistent with a Two-process model of serial dependence in which the persistence of readout weights in a decision unit compensates for sensory adaptation, leading to attractive biases in sequential perception. We propose a unified account of serial dependence in which functionally distinct mechanisms, operating at different stages, promote the differentiation and integration of visual information over time.


Assuntos
Tomada de Decisões/fisiologia , Percepção Visual/fisiologia , Adulto , Feminino , Humanos , Masculino , Modelos Teóricos , Visão Ocular/fisiologia , Adulto Jovem
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