LIMITING FACTORS IN NORMAL AND AMBLYOPIC SPATIAL VISION

Summary

Principal Investigator: DENNIS MICHAEL LEVI
Affiliation: University of California
Country: USA
Abstract: Our long-range objective is to understand the mechanisms that limit spatial vision in humans with amblyopia. We propose to test a number of specific hypotheses and predictions about these factors, and to assess the limits and mechanisms of neural plasticity in adults and children with amblyopia. Aim 1. Crowding. Feature binding and positional uncertainty in amblyopic and peripheral vision: We hypothesize that both crowding and anomalous feature binding in peripheral and amblyopic vision can be explained by limits imposed by early processes in cortical area V1. We propose a series of experiments, using novel methods and modeling, to answer the following questions: i) Do feature binding and crowding share the same spatial properties? ii) Is there mis-mapping of retinal location to perceived visual space in amblyopia, and is this the result of mis-wiring within feature maps or mis-registration between them? An Adaptive Optics Scanning Laser Ophthalmoscope allows us to deliver point stimuli to precisely identifiable single cones in the retina, and evaluate their perceived location iii) Does crowding impose a critical limit on reading in peripheral and amblyopic vision? Aim 2. Deficits exist at multiple levels in the amblyopic visual system: Recent results lead to the hypothesis that although dysfunction within the amblyopic visual system first occurs in area V1, it is amplified downstream. We will test the prediction that amblyopes will show deficits in "higher level" tasks that cannot be explained by low level considerations: i) second-order processing, ii) contour integration, and iii) temporal, spatial and/or capacity limits of attention. Aim 3. Neural Plasticity in normal and amblyopic vision: There is a surprising degree of neural plasticity in both normal and amblyopic adults as evidenced by perceptual learning, i) We will test the hypothesis that perceptual learning occurs at a high level and reflects the brain learning to attend to and use the most reliable information for the task, ii) Assess the time course, limits and mechanisms of plasticity in adults and young children with amblyopia undergoing both perceptual learning and clinical treatment. We predict that improvement following the successful treatment of amblyopia involves the same mechanisms that improve normal vision following perceptual learning, iii) We will test the prediction that the successful effects of treatment or perceptual learning in amblyopia will lead to increased foveal activation in the visual cortex, as evidenced by alterations in functional MRI.
Funding Period: 1976-05-01 - 2011-11-30
more information: NIH RePORT

Top Publications

  1. ncbi Stochastic model for detection of signals in noise
    Stanley A Klein
    School of Optometry, University of California, Berkeley, Berkeley, California 94720, USA
    J Opt Soc Am A Opt Image Sci Vis 26:B110-26. 2009
  2. ncbi Temporal dynamics of directional selectivity in human vision
    Peter Neri
    School of Optometry and Helen Wills Neuroscience Institute, University of California at Berkeley, Berkeley, CA 94720, USA
    J Vis 8:22.1-11. 2008
  3. ncbi Crowding between first- and second-order letters in amblyopia
    Susana T L Chung
    College of Optometry and Center for Neuro Engineering and Cognitive Science, University of Houston, Houston, TX, USA
    Vision Res 48:788-98. 2008
  4. ncbi Crowding--an essential bottleneck for object recognition: a mini-review
    Dennis M Levi
    University of California at Berkeley, School of Optometry and The Helen Wills Neuroscience Institute, Berkeley, CA 94720 2020, USA
    Vision Res 48:635-54. 2008
  5. ncbi Amblyopic reading is crowded
    Dennis M Levi
    School of Optometry and Helen Wills Neuroscience Institute, UC Berkeley, Berkeley, CA 94720 2020, USA
    J Vis 7:21.1-17. 2007
  6. ncbi Crowding and surround suppression: not to be confused
    Yury Petrov
    Psychology Department, Northeastern University, Boston, MA 02115, USA
    J Vis 7:12.1-9. 2007
  7. ncbi Crowding between first- and second-order letter stimuli in normal foveal and peripheral vision
    Susana T L Chung
    College of Optometry and Center for Neuro Engineering and Cognitive Science, University of Houston, Houston, TX, USA
    J Vis 7:10.1-13. 2007
  8. ncbi Crowding is directed to the fovea and preserves only feature contrast
    Yury Petrov
    Psychology Department, Northeastern University, Boston, MA 02115, USA
    J Vis 7:8.1-9. 2007
  9. ncbi The wallpaper illusion explained
    Suzanne P McKee
    Smith Kettlewell Eye Research Institute, San Francisco, CA 94115, USA
    J Vis 7:10.1-11. 2007
  10. ncbi Extended perceptual learning results in substantial recovery of positional acuity and visual acuity in juvenile amblyopia
    Roger W Li
    School of Optometry, University of California Berkeley, Berkeley, CA 94720 2020, USA
    Invest Ophthalmol Vis Sci 48:5046-51. 2007

Scientific Experts

Detail Information

Publications48

  1. ncbi Stochastic model for detection of signals in noise
    Stanley A Klein
    School of Optometry, University of California, Berkeley, Berkeley, California 94720, USA
    J Opt Soc Am A Opt Image Sci Vis 26:B110-26. 2009
    ..In addition, we modify present models to better handle detection of signals with both noise and pedestal backgrounds...
  2. ncbi Temporal dynamics of directional selectivity in human vision
    Peter Neri
    School of Optometry and Helen Wills Neuroscience Institute, University of California at Berkeley, Berkeley, CA 94720, USA
    J Vis 8:22.1-11. 2008
    ..We successfully modeled this bimodal behavior using a simple circuit where each directional filter normalizes its own output, with the normalizing signal delayed by approximately 100 ms...
  3. ncbi Crowding between first- and second-order letters in amblyopia
    Susana T L Chung
    College of Optometry and Center for Neuro Engineering and Cognitive Science, University of Houston, Houston, TX, USA
    Vision Res 48:788-98. 2008
    ..Our findings are consistent with the hypothesis that crowding results from an abnormal integration of target and flankers beyond the stage of feature detection, which takes place over a large distance in amblyopic vision...
  4. ncbi Crowding--an essential bottleneck for object recognition: a mini-review
    Dennis M Levi
    University of California at Berkeley, School of Optometry and The Helen Wills Neuroscience Institute, Berkeley, CA 94720 2020, USA
    Vision Res 48:635-54. 2008
    ..A full understanding of crowding may allow us to understand this bottleneck to object recognition and the rules that govern the integration of features into objects...
  5. ncbi Amblyopic reading is crowded
    Dennis M Levi
    School of Optometry and Helen Wills Neuroscience Institute, UC Berkeley, Berkeley, CA 94720 2020, USA
    J Vis 7:21.1-17. 2007
    ..The uncrowded-span model of normal reading fits the amblyopic results well, with a roughly fivefold increase in the critical spacing at fixation. Thus, the entire amblyopic reading deficit is accounted for by crowding...
  6. ncbi Crowding and surround suppression: not to be confused
    Yury Petrov
    Psychology Department, Northeastern University, Boston, MA 02115, USA
    J Vis 7:12.1-9. 2007
    ..Surround suppression apparently dominates at low contrasts, which would explain some of the reported similarities between the two phenomena...
  7. ncbi Crowding between first- and second-order letter stimuli in normal foveal and peripheral vision
    Susana T L Chung
    College of Optometry and Center for Neuro Engineering and Cognitive Science, University of Houston, Houston, TX, USA
    J Vis 7:10.1-13. 2007
    ..Our finding of substantial interaction between first- and second-order stimuli suggests that the processing of these stimuli is not independent at the stage of processing at which crowding occurs...
  8. ncbi Crowding is directed to the fovea and preserves only feature contrast
    Yury Petrov
    Psychology Department, Northeastern University, Boston, MA 02115, USA
    J Vis 7:8.1-9. 2007
    ..Thus, crowding appears to spare only the most salient peripheral information, which supports the hypothesis that crowding is caused by limitations of attentional resolution...
  9. ncbi The wallpaper illusion explained
    Suzanne P McKee
    Smith Kettlewell Eye Research Institute, San Francisco, CA 94115, USA
    J Vis 7:10.1-11. 2007
    ..We speculate that access to the most sensitive V1 neurons depends on the extrastriate processes that determine perceived depth--in this case, second-order envelope mechanisms...
  10. ncbi Extended perceptual learning results in substantial recovery of positional acuity and visual acuity in juvenile amblyopia
    Roger W Li
    School of Optometry, University of California Berkeley, Berkeley, CA 94720 2020, USA
    Invest Ophthalmol Vis Sci 48:5046-51. 2007
    ..The present study was conducted to determine whether extended training is necessary for optimal treatment of amblyopia...
  11. ncbi Attentional blinks as errors in temporal binding
    Ariella V Popple
    School of Optometry and Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, CA 94720 2020, USA
    Vision Res 47:2973-81. 2007
    ..We suggest that this disruption occurs within a certain time (approximately 0.5 s) after the first target, during which period salient distractors are as likely as the second target to enter working memory...
  12. ncbi Integration across Time Determines Path Deviation Discrimination for Moving Objects
    David Whitaker
    Department of Optometry, University of Bradford, Bradford, United Kingdom
    PLoS ONE 3:e1930. 2008
    ..In this study we characterize our ability to judge changes in the direction of motion of objects-a common task which can allow us either to intercept moving objects, or else avoid them if they pose a threat...
  13. ncbi What limits performance in the amblyopic visual system: seeing signals in noise with an amblyopic brain
    Dennis M Levi
    School of Optometry and Helen Wills Neuroscience Institute, UC Berkeley, Berkeley, CA 94720 2020, USA
    J Vis 8:1.1-23. 2008
    ..This loss is more or less independent of external noise contrast over a log unit range of external noise...
  14. ncbi Amblyopia masks the scale invariance of normal central vision
    Dennis M Levi
    School of Optometry and Helen Wills Neuroscience Institute, UC Berkeley, Berkeley, CA, USA
    J Vis 9:22.1-11. 2009
    ....
  15. ncbi The time course of contrast masking reveals two distinct mechanisms of human surround suppression
    Yury Petrov
    Department of Psychology, Northeastern University, Boston, MA, USA
    J Vis 9:21.1-11. 2009
    ....
  16. ncbi Perceptual learning as a potential treatment for amblyopia: a mini-review
    Dennis M Levi
    School of Optometry and The Helen Wills Neuroscience Institute, University of California, Berkeley, CA 94720 2020, United States
    Vision Res 49:2535-49. 2009
    ..The success of PL raises the question of whether it should become a standard part of the armamentarium for the clinical treatment of amblyopia, and suggests several important principles for effective perceptual learning in amblyopia...
  17. ncbi The attentional blink in amblyopia
    Ariella V Popple
    School of Optometry and Helen Wills Neuroscience Institute, University of California at Berkeley, Berkeley, CA, USA
    J Vis 8:12.1-9. 2008
    ..These findings highlight the role of early (monocular) visual processes in modulating the attentional blink, as well as the role of attention in amblyopic visual deficits...
  18. ncbi Prolonged perceptual learning of positional acuity in adult amblyopia: perceptual template retuning dynamics
    Roger W Li
    School of Optometry and The Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, California 94720 2020, USA
    J Neurosci 28:14223-9. 2008
    ..These results show that the mature amblyopic brain is surprisingly malleable, and point to more intensive treatment methods for amblyopia...
  19. ncbi Complete transfer of perceptual learning across retinal locations enabled by double training
    Lu Qi Xiao
    State Key Laboratory of Cognitive Neuroscience and Learning, Beijing Normal University, Beijing 100875, China
    Curr Biol 18:1922-6. 2008
    ....
  20. ncbi Improving the performance of the amblyopic visual system
    Dennis M Levi
    School of Optometry and The Helen Wills Neuroscience Institute, University of California, Berkeley, CA 94720 2020, USA
    Philos Trans R Soc Lond B Biol Sci 364:399-407. 2009
    ..These findings, along with the results of new clinical trials, suggest that it might be time to reconsider our notions about neural plasticity in amblyopia...
  21. ncbi Evidence for joint encoding of motion and disparity in human visual perception
    Peter Neri
    Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
    J Neurophysiol 100:3117-33. 2008
    ..Both components are involved in the perception of stimuli containing motion and disparity information in line with the known existence of corresponding neuronal subpopulations in visual cortex...
  22. ncbi Learning to identify near-threshold luminance-defined and contrast-defined letters in observers with amblyopia
    Susana T L Chung
    School of Optometry, University of California, 360 Minor Hall, Berkeley, CA 94720 2020, USA
    Vision Res 48:2739-50. 2008
    ..Our findings are consistent with predictions based on the locus of learning for first- and second-order stimuli according to the filter-rectifier-filter model for second-order visual processing...
  23. ncbi On the effective number of tracked trajectories in amblyopic human vision
    Srimant P Tripathy
    Division of Optometry, School of Life Sciences, University of Bradford, Bradford, United Kingdom
    J Vis 8:8.1-22. 2008
    ..A comparison with data previously published for normal eyes failed to reveal any deficit in the effective number of trajectories tracked by the non-amblyopic eyes of amblyopic observers for the current task...
  24. ncbi The response of the amblyopic visual system to noise
    Dennis M Levi
    University of California, Berkeley, School of Optometry and The Helen Wills Neuroscience Institute, Berkeley, CA 94720 2020, USA
    Vision Res 47:2531-42. 2007
    ..However, for the discrimination of suprathreshold white noise contrast, there is surprisingly little additional deficit, after accounting for the visibility of the noise...
  25. ncbi Collinearity improves alignment in amblyopia as well as in normal vision
    Ariella V Popple
    Optometry, UC Berkeley, CA 94720 2020, USA
    Vision Res 47:1968-73. 2007
    ....
  26. ncbi Learning to identify contrast-defined letters in peripheral vision
    Susana T L Chung
    College of Optometry and Center for Neuro Engineering and Cognitive Science, University of Houston, Houston, TX, USA
    Vision Res 46:1038-47. 2006
    ..The complete interocular transfer, and the retinotopic (retinal location) and size specificity of the learning effect are consistent with the properties of neurons in early visual area V2...
  27. ncbi Perceptual learning improves visual performance in juvenile amblyopia
    Roger W Li
    School of Optometry and Helen Wills Neuroscience Institute, University of California-Berkeley, Berkeley, CA 94720-2020, USA
    Invest Ophthalmol Vis Sci 46:3161-8. 2005
    ..The improvement can be parsed into two important factors: decreased equivalent input noise and increased efficiency. Perceptual learning techniques may add an effective new method to the armamentarium of amblyopia treatments...
  28. ncbi Spatial interactions reveal inhibitory cortical networks in human amblyopia
    Erwin H Wong
    School of Optometry, University of California, Berkeley, CA 94720, USA
    Vision Res 45:2810-9. 2005
    ..Furthermore, strabismic observers with no loss of visual acuity show a similar pattern of detection suppression. We speculate that amblyopia results in predominantly inhibitory cortical interactions between second-order neurons...
  29. ncbi Second-order spatial summation in amblyopia
    Erwin H Wong
    School of Optometry, University of California, Berkeley, CA 94720, USA
    Vision Res 45:2799-809. 2005
    ..We conclude that the pooling of second-order contrast across visual space is unaffected by amblyopia...
  30. ncbi What is the signal in noise?
    Dennis M Levi
    University of California, Berkeley, School of Optometry and The Helen Wills Neuroscience Institute, Berkeley, CA 94720 2020, USA
    Vision Res 45:1835-46. 2005
    ..Surprisingly, we found that the human template is "adaptive"-- its shape depends on the spatial frequency band of the noise-suggesting that sensitivity to spatial noise is not simply determined via passive filtering...
  31. ncbi "Phase capture" in amblyopia: the influence function for sampled shape
    Dennis M Levi
    University of California, Berkeley, School of Optometry and Helen Wills Neuroscience Institute, Berkeley, CA 94720 2020, USA
    Vision Res 45:1793-805. 2005
    ..We speculate that this may be a consequence of abnormal "crowding" of the inner patches by the outer ones...
  32. ncbi Location coding by the human visual system: multiple topological adaptations in a case of strabismic amblyopia
    Ariella V Popple
    School of Optometry, University of California at Berkeley, Berkeley, CA 94720 2020, USA
    Perception 34:87-107. 2005
    ..Instead, the observed behavior suggests that multiple adaptations of the underlying cortical topology are possible simultaneously in different parts of the visual field...
  33. ncbi Perceptual learning in adults with amblyopia: a reevaluation of critical periods in human vision
    Dennis M Levi
    School of Optometry and Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720 2020, USA
    Dev Psychobiol 46:222-32. 2005
    ..It is hypothesized that these same mechanisms account for at least some of the improvement that occurs in the treatment of amblyopia...
  34. ncbi Learning letter identification in peripheral vision
    Susana T L Chung
    College of Optometry and Center for Neuro Engineering and Cognitive Science, University of Houston, 505 J Davis Armistead Bldg, Houston, TX 77204 2020, USA
    Vision Res 45:1399-412. 2005
    ..Results from both the PTM analysis and the double-pass experiment imply that the stimulus-dependent component of the internal noise does not change with learning...
  35. ncbi The perception of spatial order at a glance
    Ariella V Popple
    School of Optometry and Helen Wills Neuroscience Institute, Berkeley, University of California at Berkeley, Gayley Road, Berkeley, CA 94720 2020, USA
    Vision Res 45:1085-90. 2005
    ..Regardless of spacing and set-size, confusions between neighbors were unexpectedly frequent, suggesting there is positional as well as object uncertainty...
  36. ncbi Two sources of error in pop-out localization
    Ariella V Popple
    School of Optometry, Helen Wills Neuroscience Institute, UC Berkeley, CA 94720 2020, USA
    Vision Res 46:293-8. 2006
    ....
  37. ncbi Spatial resolution for feature binding is impaired in peripheral and amblyopic vision
    Peter Neri
    School of Optometry and Helen Wills Neuroscience Institute, University of California, Berkeley, CA 94720 2020, USA
    J Neurophysiol 96:142-53. 2006
    ..Our results in persons with amblyopia indicate that the ability of the fovea to compensate for this poor co-registration is consolidated by visual experience during postnatal development...
  38. ncbi Image segregation in strabismic amblyopia
    Dennis M Levi
    School of Optometry and Helen Wills Neuroscience Institute, University of California, Berkeley, CA 94720 2020, USA
    Vision Res 47:1833-8. 2007
    ..I therefore conclude that these deficits are not a consequence of abnormal segregation of figure from background...
  39. ncbi Sensitivity to biological motion drops by approximately 1/2 log-unit with inversion, and is unaffected by amblyopia
    Peter Neri
    School of Optometry, University of California at Berkeley, Berkeley, CA 94720 2020, USA
    Vision Res 47:1209-14. 2007
    ..Our data provide a quantitative estimate of the inversion effect for biological motion, and demonstrate that higher-level processing in the motion hierarchy is not affected by amblyopia...
  40. ncbi Global contour processing in amblyopia
    Dennis M Levi
    School of Optometry and Helen Wills Neuroscience Institute, University of California, Berkeley, CA 94720 2020, USA
    Vision Res 47:512-24. 2007
    ..The residual deficits reported here cannot be simply ascribed to reduced visibility or increased positional uncertainty, and we therefore conclude that these are genuine deficits in global contour segregation and integration...
  41. ncbi Is the ability to identify deviations in multiple trajectories compromised by amblyopia?
    Dennis M Levi
    School of Optometry and Helen Wills Neuroscience Institute, UC Berkeley, Berkeley, CA 94720 2020, USA
    J Vis 6:1367-79. 2006
    ..We conclude that while amblyopia disrupts static angle discrimination, amblyopic dynamic deviation detection thresholds are normal or very nearly so...
  42. ncbi Temporal dynamics of figure-ground segregation in human vision
    Peter Neri
    School of Optometry, University of California at Berkeley, Berkeley, CA, USA
    J Neurophysiol 97:951-7. 2007
    ..Figure enhancement within this narrow temporal window was transient rather than sustained as may be expected from measurements in single neurons. These psychophysical results prompt and guide further electrophysiological studies...
  43. ncbi Meaningful interactions can enhance visual discrimination of human agents
    Peter Neri
    School of Optometry, University of California at Berkeley, Berkeley, California 94720 2020, USA
    Nat Neurosci 9:1186-92. 2006
    ..Our results demonstrate that action understanding has a pervasive impact on the human ability to extract visual information from the actions of other humans, providing quantitative evidence of its significance for sensory performance...
  44. ncbi Identification of contrast-defined letters benefits from perceptual learning in adults with amblyopia
    Susana T L Chung
    College of Optometry and Center for Neuro Engineering and Cognitive Science, University of Houston, Houston, TX, USA
    Vision Res 46:3853-61. 2006
    ....
  45. ncbi The receptive field and internal noise for position acuity change with feature separation
    Roger W Li
    School of Optometry and Helen Wills Neuroscience Institute, University of California, Berkeley, CA 94720, USA
    J Vis 6:311-21. 2006
    ..Although systematic internal noise is thought to be one of the important components limiting detection thresholds, we found that systematic noise is negligible in our position task...
  46. ncbi Receptive versus perceptive fields from the reverse-correlation viewpoint
    Peter Neri
    School of Optometry, University of California, 360 Minor Hall, Berkeley, CA 94720 2020, USA
    Vision Res 46:2465-74. 2006
    ....
  47. ncbi Visual processing in amblyopia: human studies
    Dennis M Levi
    University of California at Berkeley, School of Optometry, Berkeley, CA 94720, USA
    Strabismus 14:11-9. 2006
    ..3) There appears to be substantial neural plasticity in the amblyopic brain beyond the "critical period."..
  48. ncbi "Crowding" in normal and amblyopic vision assessed with Gaussian and Gabor C's
    Srividhya Hariharan
    College of Optometry, University of Houston, Houston, TX 77204-6052, USA
    Vision Res 45:617-33. 2005
    ..Instead we suggest that crowding in amblyopic and peripheral vision is a result of extended pooling at a stage following the stage of feature detection...