Research Topics
| P J BexSummaryAffiliation: University College London Country: UK Publications
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Detail Information
Publications
Resolution of complex motion detectors in the central and peripheral visual fieldPeter J Bex
Institute of Ophthalmology, University College London, London EC1V 9EL, UK
J Opt Soc Am A Opt Image Sci Vis 23:1598-607. 2006..However, such pooling limits the precision with which multiple looming objects can be discriminated, especially in the peripheral visual field...- Critical band masking in optic flowPeter J Bex
Division of Visual Rehabilitation Research, The Institute of Ophthalmology, London, UK
Network 16:261-84. 2005..Our results suggest that visual processing normalises responses to supra-threshold structure at different spatial and temporal frequencies within natural stimuli and so equates their effective visibility... - Spatial interference among moving targetsPeter J Bex
Institute of Ophthalmology, University College London, 11 43 Bath Street, London EC1V 9EL, UK
Vision Res 45:1385-98. 2005..The underlying connectivity of this integration favours low spatial frequency structure but is broadly tuned for speed... - The shape and size of crowding for moving targetsPeter J Bex
Institute of Ophthalmology, University College London, 11 43 Bath Street, London EC1V 9EL, UK
Vision Res 43:2895-904. 2003..These results reveal asymmetrical space-time dependent regions of visual integration that are radially organised about central vision... - Grouping local directional signals into moving contoursPeter J Bex
Institute of Ophthalmology, 11 43 Bath Street, EC1V 9EL, London, UK
Vision Res 43:2141-53. 2003..The visibility of these moving contours identifies narrow-band grouping processes that are sensitive to the shape defined by the directions of the elements forming the contour... - Motion detection and the coincidence of structure at high and low spatial frequenciesPeter J Bex
Institute of Ophthalmology, 11 43 Bath Street, EC1V 9EL, London, UK
Vision Res 43:371-83. 2003..Both are required to account for the two results, and they appear to operate under very similar conditions... - Spatial frequency, phase, and the contrast of natural imagesPeter J Bex
Institute of Ophthalmology, London, UK
J Opt Soc Am A Opt Image Sci Vis 19:1096-106. 2002..We argue that these observations are consistent with changes in the activity within spatial-frequency channels caused by the higher-order phase structure of natural images that is responsible for the presence of edges and specularities... - Snakes and ladders: the role of temporal modulation in visual contour integrationP J Bex
Institute of Ophthalmology, 11 43 Bath Street, London EC1V 9EL, UK
Vision Res 41:3775-82. 2001..These results lend further support to the notion that the contour integration system receives separate transient and sustained input... - Comparison of the spatial-frequency selectivity of local and global motion detectorsPeter J Bex
Institute of Ophthalmology, London, UK
J Opt Soc Am A Opt Image Sci Vis 19:670-7. 2002..e., they integrate across a broad range of spatial frequencies), with a preference for low spatial frequencies... - Local and global visual grouping: tuning for spatial frequency and contrastS C Dakin
Institute of Ophthalmology, University College London, London, United Kingdom
J Vis 1:99-111. 2001..We conclude that local grouping is consistent with the use of simple-oriented filtering mechanisms. Global grouping seems to depend more on the visibility of elements that can be affected by both spatial frequency and contrast... - Dissociable effects of attention and crowding on orientation averagingSteven C Dakin
UCL Institute of Ophthalmology, University College London, London, UK
J Vis 9:28.1-16. 2009.... - Illusory stimuli can be used to identify retinal blind spotsMichael D Crossland
University College London Institute of Ophthalmology, London, United Kingdom
PLoS ONE 2:e1060. 2007.... - Contrast adaptation implies two spatiotemporal channels but three adapting processesKeith Langley
Department of Psychology, University College London, UK
J Exp Psychol Hum Percept Perform 33:1283-96. 2007.... - The twinkle aftereffect is pre-cortical and is independent of filling-inMichael D Crossland
UCL Institute of Ophthalmology, London, UK
J Vis 8:13.1-10. 2008..These results indicate that the TwAE involves additive noise that is pre-cortical in origin and that it is distinct from filling-in... - Spatial alignment over retinal scotomasMichael D Crossland
University College London Institute of Ophthalmology, London, United Kingdom
Invest Ophthalmol Vis Sci 50:1464-9. 2009..Similarities between the completion of pathologic and physiological scotomas would be consistent with large-scale reorganization of the visual system in eye disease.. - Crowding changes appearanceJohn A Greenwood
UCL Institute of Ophthalmology, University College London, 11 43 Bath Street, London EC1V9EL, UK
Curr Biol 20:496-501. 2010..These results confirm predictions from change-based models of crowding, such as averaging, and establish crowding as a regularization process that simplifies the peripheral field by promoting consistent appearance among adjacent objects... - Positional averaging explains crowding with letter-like stimuliJohn A Greenwood
UCL Institute of Ophthalmology, University College London, 11 43 Bath Street, London EC1V 9EL, United Kingdom
Proc Natl Acad Sci U S A 106:13130-5. 2009..Together, our results suggest that crowding is a preattentive process that uses averaging to regularize the noisy representation of position in the periphery... - The aperture problem in contoured stimuliDavid Kane
UCL Institute of Ophthalmology, University College London, London EC1V 9EL, United Kingdom
J Vis 9:13.1-17. 2009..We report that global motion integration is (a) largely insensitive to the second-order statistics of such stimuli and (b) is rigidly broadband even in the presence of a disrupted low SF component... - Probabilistic, positional averaging predicts object-level crowding effects with letter-like stimuliSteven C Dakin
Institute of Ophthalmology, University College London, London, UK
J Vis 10:14. 2010..Thus, we demonstrate a set of seemingly "high-level" object-centered crowding effects that can arise from "low-level" interactions between the features of letter-like elements... - Dynamic properties of orientation discrimination assessed by using classification imagesIsabelle Mareschal
Institute of Ophthalmology, University College London, Bath Street, London EC1V 9EL, United Kingdom
Proc Natl Acad Sci U S A 103:5131-6. 2006.... - Role of synchrony in contour binding: some transient doubts sustainedSteven C Dakin
Institute of Ophthalmology, University College London, UK
J Opt Soc Am A Opt Image Sci Vis 19:678-86. 2002.... - Perceived blur in amblyopiaAnita J Simmers
Institute of Ophthalmology, University College London, London, United Kingdom
Invest Ophthalmol Vis Sci 44:1395-400. 2003..In the current study, the representation of blur in amblyopia with blur-discrimination and blur-matching tasks was explored in a series of experiments... - Natural image statistics mediate brightness 'filling in'Steven C Dakin
Department of Visual Science, Institute of Ophthalmology, University College London, 11 43 Bath Street, London EC1V 9EL, UK
Proc Biol Sci 270:2341-8. 2003..As predicted by the model, the filling-in process is contingent on the presence of appropriate low SF structure... - The representation of global spatial structure in amblyopiaAnita J Simmers
The Institute of Ophthalmology, University College London, EC1V 9EL London, UK
Vision Res 44:523-33. 2004..It is this increased spatial uncertainty that underlies the spatial deficit in amblyopia... - Local and global limitations on direction integration assessed using equivalent noise analysisSteven C Dakin
Department of Visual Science, Institute of Ophthalmology, University College London, 11 43 Bath Street, London EC1V 9EL, UK
Vision Res 45:3027-49. 2005..A population vector-averaging scheme (essentially a special case of ML estimation) produces similar predictions but out-performs subjects at high levels of directional variability and fails to predict motion coherence thresholds... - An oblique effect for local motion: psychophysics and natural movie statisticsSteven C Dakin
Institute of Ophthalmology, University College London, Bath Street, London, United Kingdom
J Vis 5:878-87. 2005..If motion detectors are optimized to deal with our visual world then such anisotropies likely explain the local nature of the OEM... - Summation of concentric orientation structure: seeing the Glass or the window?S C Dakin
Institute of Ophthalmology, University College London, 11 43 Bath Street, London EC1V 9EL, UK
Vision Res 42:2013-20. 2002..We conclude that this paradigm presently offers no concrete psychophysical evidence for specialised concentric orientation detectors... - Deficit of visual contour integration in dyslexiaA J Simmers
Department of Visual Rehabilitation, Institute of Ophthalmology, University College London, United Kingdom
Invest Ophthalmol Vis Sci 42:2737-42. 2001..In the present study a contour integration task was used to investigate such perceptual organization in dyslexia... - Contextual modulation of the motion aftereffectHelle K Falkenberg
Institute of Ophthalmology, University College London, London, UK
J Exp Psychol Hum Percept Perform 33:257-70. 2007..Collectively, these results suggest that motion processing, similar to texture processing, is organized for the purpose of highlighting regions of directional discontinuity in retinal images... - The perception of suprathreshold contrast and fast adaptive filteringPeter J Bex
Schepens Eye Research Institute, Harvard Medical School, Boston, MA 02114, USA
J Vis 7:1.1-23. 2007.... - Sources of motion-sensitivity loss in glaucomaHelle K Falkenberg
Department of Optometry and Vision Science, Buskerud University College, Kongsberg, Norway
Invest Ophthalmol Vis Sci 48:2913-21. 2007..In this study, a signal-to-noise motion-sensitivity task was used to investigate the sources of motion-sensitivity loss in patients with POAG... - Contrast conservation in human visionJozsef Fiser
Center for Visual Science, University of Rochester, Rochester, NY 14627 0268, USA
Vision Res 43:2637-48. 2003.... - Acuity, crowding, reading and fixation stabilityHelle K Falkenberg
Department of Optometry and Visual Science, Buskerud University College, Frogsvei 41, 3601 Kongsberg, Norway
Vision Res 47:126-35. 2007..The results suggest that unstable fixation may contribute to reading difficulties in people with low vision and therefore that rehabilitation may benefit from fixation training... - Contrast gain control in natural scenesPeter J Bex
Schepens Eye Research Institute, Harvard Medical School, Boston, MA 02114, USA
J Vis 7:12.1-12. 2007..This process tends to normalize the response of the visual system across natural scenes, which contain uneven contrast distributions...