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Vision after complete blindness: Mike May

Vision after complete blindness: Mike May. Fine et al., Nature Neuroscience 2003; Robert Kurzon, ‘Crashing Through’. We tend to take normal perception for granted, while finding bizarre experiences of exceptional individuals intriguing…. But understanding normal perception is the toughest

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Vision after complete blindness: Mike May

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  1. Vision after complete blindness: Mike May Fine et al., Nature Neuroscience 2003; Robert Kurzon, ‘Crashing Through’

  2. We tend to take normal perception for granted, while finding bizarre experiences of exceptional individuals intriguing… But understanding normal perception is the toughest and most important challenge for psychology Occasionally, though, an exceptional individual’s experience can advance our understanding of normal perception… For instance, the case of Mike May helps us not to take perception for granted

  3. To what extent does visual processing rely on visual experience?

  4. Ione Fine (UCSD USC)

  5. Ione Fine (UCSD USC) Geoff Boynton (UCSD/Salk): fMRI+

  6. Ione Fine (UCSD USC) Brian Wandell (Stanford) and Alex Wade, Alissa Brewer (Stanford) Geoff Boynton (UCSD/Salk): fMRI+

  7. Ione Fine (UCSD USC) Brian Wandell (Stanford) Alex Wade, Alissa Brewer (Stanford) Geoff Boynton (UCSD/Salk): fMRI+ Stuart Anstis (UCSD)

  8. Subject Mike May • Blinded by a chemical accident at age 3. • Light sensitive (no form vision) between ages of 3-43

  9. Subject Mike May • Sight restored by a new procedure - • Corneal epithelial stem cell replacement

  10. Resolution • 2 & 3d Form • Motion • Object/Face Recognition

  11. Contrast-Sensitivity Function (CSF) Sensitivity Spatial frequency (cycles/degree) Campbell & Robson (1968) Resolution limit: 50cpd

  12. Resolution limit < 2 cpd, despite good optics 2 1.5 Log sensitivity 1 MM (Post-operatively) Normal 0.5 0 0 1 2 3 Spatial frequency (c/deg)

  13. No improvement over time 2 MM + 5 months MM +11 months MM +17 months MM +21 months CONTROL 1.5 Log sensitivity 1 0.5 0 0 1 2 3 Spatial frequency (c/deg)

  14. 2D FORM MM could identify simple shapes

  15. 2D FORM …but not shapes defined by illusory contours.

  16. 2D FORM Mike can identify simple 2d forms (100% correct) Letters recognizable But “constructive” 2d perception is harder MM = 80%; controls=100%, 90%, 95%) MM = 73%; controls = 80%, 85%, 100% guessing

  17. 3D FORM Sensitive (100% correct) to occlusion …

  18. 3D FORM Shading gave no automatic impression of depth: The circle was seen as a flat disc, with non-uniform surface lightness

  19. 3D FORM Fails with: Shape from Shading: Perspective: “A square with lines attached”

  20. MOTION Could NOT recognize a stationary cube from any angle - “square with lines”

  21. Couldn’t identify STATIC cube…but with a ROTATING one, “It’s a cube! …going in …going out”

  22. MOTION Could NOT recognize a stationary cube from any angle - “square with lines”

  23. MOTION Could NOT recognize a stationary cube from any angle - “square with lines” YET … Can exploit motion to construct 3D structure- “it’s a cube! …moving in, moving out”

  24. MOTION Could make sense of… Point-light walker Rotational Glass patterns Structure from motion (100% correct) MM = 90%; controls=95%, 80%, 85%).

  25. Sophisticated processing of MOTION: • Can see form from motion (KDE cube) • Saw depth in face masks by rocking his head • Could see Johansson’s walking man • Can play catch • Skiing: vision now helps!

  26. Motion SB (Ackroyd et al) “His only signs of appreciation were to moving objects, particularly the pigeons in Trafalgar square… He clearly enjoyed … watching … the movement of other cars on the road …He spotted a speeder coming up very fast behind us” Virgil (Sacks) “when [the gorilla] finally came into the open he thought that, though it moved differently, it looked just like a large man”

  27. Poor object & face identification MM 25% correct control 100% Gender MM 70% correctcontrol 100% Expression (happy/sad/neutral) MM 61% correct control 100%

  28. Clinton&Gore By Sinha &Poggio

  29. These dissociations between form and motion tasks were consistent with the size and activation of visual areas measured using fMRI V1 and (especially) extrastriate areas in the temporal stream, thought to be responsible for form processing, were small and showed low activity levels. The Medial Temporal complex, thought to be responsible for motion processing, was normal in both size and activation

  30. control observers MM Size of V1 and MT+ 35 30 25 20 Surface area (cm2) 15 10 5 0 V1 (L) V1 (R) MT+ (L) MT+ (R) Cortical area

  31. “The eye of the artist” Matches projective shapes, not real shapes, e.g. NOT susceptible to Shepard’s illusion: Tables have the SAME projective shape, and to MM they look the same

  32. “flat world” Matches projective shapes, not real shapes, e.g. NOT susceptible to Shepard’s illusion: Tables have the SAME projective shape, and to MM they look the same

  33. “flat world” Matches projective shapes, not real shapes, e.g. NOT susceptible to Shepard’s illusion: Tables have the SAME projective shape, and to MM they look the same

  34. “flat world” Matches projective shapes, not real shapes, e.g. NOT susceptible to Shepard’s illusion: Tables have the SAME projective shape, and to MM they look the same

  35. “flat world” Matches projective shapes, not real shapes, e.g. NOT susceptible to Shepard’s illusion: Tables have the SAME projective shape, and to MM they look the same

  36. “flat world” Matches projective shapes, not real shapes, e.g. NOT susceptible to Shepard’s illusion: Tables have the SAME projective shape, and to MM they look the same

  37. “flat world” Matches projective shapes, not real shapes, e.g. NOT susceptible to Shepard’s illusion: Tables have the SAME projective shape, and to MM they look the same

  38. “flat world” Matches projective shapes, not real shapes, e.g. NOT susceptible to Shepard’s illusion: Tables have the SAME projective shape, and to MM they look the same

  39. “flat world” Matches projective shapes, not real shapes, e.g. NOT susceptible to Shepard’s illusion: Tables have the SAME projective shape, and to MM they look the same

  40. Mike correctly sees the diamonds as similar in lightness, and responds photometrically to illumination and shadow in pictures, seeing shadows as dark things. http://psylux.psych.tu-dresden.de/i1/kaw/diverses%20Material/www.illusionworks.com/html/shadow.html Images from Ted Adelson

  41. Phenomenal Regression to the Real Object • Normally sighted subjects cannot retrieve any aspect of experience that is a function of retinal illuminance or projected size. But MM has these (and nothing else) available to undirected introspection. In this sense he is free (unfortunately), of the good ‘illusions’ on which normal vision is founded. • One example of resulting difficulties: Shadows at the edges of sidewalks appeared to him as black ridges that could present a potential hazard in walking

  42. Phenomenal Regression to the Real Object • Why can’t we see and judge what’s present at the sensory input, as MM can? • William James wrote: “Pure sensations can only be realised in the earliest days of life. They are all but impossible to adults with memories and stores of association acquired." • For MM (though NOT necessarily for a newborn: Granrud), James may be right, perhaps because the irrepressible interpretative processes of the normally sighted brain are not involved. • For the normally sighted, interpretation is not an integument that can be peeled away to reveal sensory bedrock: it penetrates all our consciousness, presumably thanks to the continuously bidirectional flow of information through the visual system. • So we have no ‘pure sensations’…but those ares all that MM has.

  43. The visual process as a causal chain Parietal (action) temporal (perception) V1 LGN

  44. The visual process as a feedback system Parietal (action) temporal (perception) V1 LGN In the normal visual system, each neural representation depends on the later ones.

  45. MM was not sensitive to perspective cues Yet he WAS susceptible to the Muller-Lyer and related illusions DEPTH

  46. Richard Gregory

  47. “Dumbbell” variant of the Muller-Lyer illusion

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