A5086169409- Visual perception and processing mechanisms
- Neural dynamics and brain function
- Ophthalmology and Visual Impairment Studies
- Face Recognition and Perception
- Visual Attention and Saliency Detection
- Retinal Development and Disorders
- Neural and Behavioral Psychology Studies
- Retinal Diseases and Treatments
- Multisensory perception and integration
- Labor Movements and Unions
- Retinal Imaging and Analysis
- Superconducting Materials and Applications
- Color perception and design
- Cognitive and developmental aspects of mathematical skills
- Aesthetic Perception and Analysis
- Functional Brain Connectivity Studies
- Retinal and Optic Conditions
- Systemic Lupus Erythematosus Research
- Color Science and Applications
- Particle Accelerators and Free-Electron Lasers
- Connexins and lens biology
- Glaucoma and retinal disorders
- Vestibular and auditory disorders
- Neurobiology and Insect Physiology Research
- Particle accelerators and beam dynamics
University College London
2016-2025
Institute of Ophthalmology
2010-2022
Moorfields Eye Hospital NHS Foundation Trust
2020
General University Hospital in Prague
2018
Charles University
2018
Jubilee Hospital
2017
University College Lahore
2015
Centre National de la Recherche Scientifique
2011-2014
Laboratoire Psychologie de la Perception
2011-2014
Université Paris Cité
2011-2014
There is considerable interest in how humans estimate the number of objects a scene context an extensive literature on we density (i.e., spacing) objects. Here, show that our sense and are intertwined. Presented with two patches, observers found it more difficult to spot differences either or numerosity when those patches were mismatched overall size, their errors consistent larger appearing both denser numerous. We propose estimated using relative response mechanisms tuned low high spatial...
Visual crowding is a breakdown in object identification that occurs cluttered scenes, process represents the principle restriction on visual performance periphery. When crowded objects are presented experimentally, key finding observers frequently report nearby flanking items instead of target. This observation has led to proposal reflects increased noise positional code for objects; although how presence might disrupt encoding remains unclear. We quantified this disruption using cross-like...
Significance Our ability to see, localize, and interact with stimuli varies depending on their location in the visual field. Here we consider source of these variations for several aspects spatial vision: crowding (the disruption object recognition clutter), localization, saccadic eye movements. We observe a range across both individuals field strong correlations between all tasks. However, number dissociations exclude possibility that arise from same representation Rather, propose “topology...
Abstract Perception is subjective. Even basic judgments, like those of visual object size, vary substantially between observers and also across the field within same observer. The way in which system determines size objects remains unclear, however. We hypothesize that inferred from neuronal population activity V1 predict idiosyncrasies cortical functional architecture should therefore explain individual differences judgments. Here we show results novel behavioural methods magnetic resonance...
Object recognition in the peripheral visual field is limited by crowding: disruptive influence of nearby clutter [1Whitney D. Levi D.M. Visual a fundamental limit on conscious perception and object recognition.Trends Cogn. Sci. (Regul. Ed.). 2011; 15: 160-168Abstract Full Text PDF PubMed Scopus (544) Google Scholar, 2Levi Crowding—an essential bottleneck for recognition: mini-review.Vision Res. 2008; 48: 635-654Crossref (687) Scholar]. Despite its severity, little known about cortical locus...
Crowding is the breakdown in object recognition that occurs cluttered visual environments [1Flom M.C. Weymouth F.W. Kahneman D. Visual resolution and contour interaction.J. Opt. Soc. Am. 1963; 53: 1026-1032Crossref PubMed Scopus (400) Google Scholar, 2Bouma H. Interaction effects parafoveal letter recognition.Nature. 1970; 226: 177-178Crossref (957) 3Levi D.M. Crowding—an essential bottleneck for recognition: A mini-review.Vision Res. 2008; 48: 635-654Crossref (679) 4Pelli D.G. Tillman K.A....
Abstract While observers are adept at judging the density of elements (e.g., in a random-dot image), it has recently been proposed that they also have an independent visual sense number. To test independence number and discrimination, we examined effects manipulating stimulus structure (patch size, element contrast, contrast-polarity) available attentional resources on both judgments. Five made series two-alternative, forced-choice discriminations based relative numerosity/density two...
Purpose: Amblyopia is a common developmental visual impairment characterized by substantial difference in acuity between the two eyes. Current monocular treatments, which promote use of affected eye occluding or blurring fellow eye, improve acuity, but are hindered poor compliance. Recently developed binocular treatments can produce rapid gains function, thought to be as result reduced interocular suppression. We set out develop an effective home-based treatment system for amblyopia that...
Abstract Recent advances in regenerative therapy have placed the treatment of previously incurable eye diseases within arms’ reach. Achromatopsia is a severe monogenic heritable retinal disease that disrupts cone function from birth, leaving patients with complete colour blindness, low acuity, photosensitivity and nystagmus. While successful gene-replacement non-primate models achromatopsia has raised widespread hopes for clinical treatment, it was yet to be determined if how these therapies...
We investigated how crowding-a breakdown in object recognition that occurs the presence of nearby distracting clutter-works for complex letter-like stimuli. Subjects reported orientation (up/down/left/right) a T target, abutted by single flanker composed randomly positioned horizontal and vertical bars. In addition to familiar retinotopic anisotropies (e.g., more crowding from eccentric flankers), we report three object-centered anisotropies. First, inversions target element were rare:...
Visual crowding is the disruptive effect of clutter on object recognition. Although most prominent in adult peripheral vision, also disrupts foveal vision typically developing children and those with strabismic amblyopia. Do these effects share same mechanism? Here we exploit observations that crowded errors are not random: Target objects appear either averaged flankers (assimilation) or replaced by them (substitution). If amblyopic developmental mechanism, then their should be similarly...
Purpose.: During development, the presence of strabismus and anisometropia frequently leads to amblyopia, a visual disorder characterized by interocular acuity differences. Although additional deficits in contrast sensitivity, crowding (the impaired recognition closely spaced objects), stereoacuity are common, relationship between these abilities is unclear. Methods.: We measured covariation four children 4 9 years age (n = 72) with strabismus, anisometropia, or mixed...
Our ability to recognize objects in peripheral vision is fundamentally limited by crowding, the deleterious effect of clutter that disrupts recognition features ranging from orientation and color motion depth. Previous research equivocal on whether this reflects a singular process all simultaneously or multiple processes affect each independently. We examined crowding for color, two allow strong test feature independence. "Cowhide" stimuli were presented 15° vision, either isolation...
Leucine-rich alpha-2-glycoprotein 1 (LRG1) is present abundantly in the microenvironment of many tumours where it contributes to vascular dysfunction, which impedes delivery therapeutics. In this work we demonstrate that LRG1 predominantly a non-internalising protein. We report development novel antibody-drug conjugate (ADC) comprising anti-LRG1 hinge-stabilised IgG4 monoclonal antibody Magacizumab coupled anti-mitotic payload monomethyl auristatin E (MMAE) via cleavable dipeptide linker...
Crowding—the deleterious influence of clutter on object recognition—disrupts the identification visual features as diverse orientation, motion, and color. It is unclear whether this occurs via independent feature-specific crowding processes (preceding feature binding process) or a singular (late) mechanism tuned for combined features. To examine relationship between crowding, we measured interactions relative position orientation. Stimuli were target cross two flanker crosses (each composed...
Abstract Recent work demonstrates that human face identification is most efficient when based on horizontal, rather than vertical, image structure. Because it unclear how this specialization for upright (compared to inverted) processing emerges in the visual system, present study aimed systematically characterize orientation sensitivity profile identification. With faces, performance a delayed match-to-sample task was highest horizontally filtered images and declined sharply with oblique...
The adult visual system is characterised by high-resolution foveal vision and a peripheral field limited crowding, the disruption to object recognition in clutter that gives summary 'gist' place of fine detail. In children, crowding elevated fovea, with estimates age where drops adult-like levels varying widely from 5 12+ years. As restricts key processes like reading, better characterisation this developmental trajectory critical. We developed methods optimised measure whereby adults...
Mutations affecting the CRB1 gene produce retinal dystrophies including early onset severe dystrophy/Leber congenital amaurosis (EOSRD/LCA), retinitis pigmentosa (RP), cone-rod dystrophy (CORD), and macular (MD). As treatment strategies advance toward clinical translation, there is a need to establish reliable outcome metrics better understand visual deficits associated with retinopathies. To this end, we measured acuity (VA) crowding (the disruptive effect of clutter on object recognition),...
Visual hallucinations occur across many clinical conditions, but can also be induced experimentally in healthy individuals, using high-frequency flicker (Ganzflicker) and sensory deprivation (Ganzfeld). It is unclear how hallucinatory proneness changes the lifespan, with prior questionnaire-based studies showing mixed results. As factors such as multi-sensory acuity loss relatively increased reliance on knowledge may increase we age, these are considered risk for hallucination proneness,...