Vision after complete blindness: Mike May Fine et al., Nature Neuroscience 2003; Robert Kurzon,...
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Transcript of Vision after complete blindness: Mike May Fine et al., Nature Neuroscience 2003; Robert Kurzon,...
Vision after complete blindness: Mike May
Fine et al., Nature Neuroscience 2003; Robert Kurzon, ‘Crashing Through’
But understanding normal perception is the toughestand most important challenge for psychology
We tend to take normal perception for granted, while findingbizarre experiences of exceptional individuals intriguing…
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
To what extent does visual processing rely on visual
experience?
Ione Fine (UCSD USC)
Ione Fine (UCSD USC)
Geoff Boynton (UCSD/Salk): fMRI+
Ione Fine (UCSD USC)
Geoff Boynton (UCSD/Salk): fMRI+
Brian Wandell (Stanford)and
Alex Wade, Alissa Brewer (Stanford)
Ione Fine (UCSD USC)
Geoff Boynton (UCSD/Salk): fMRI+
Brian Wandell (Stanford)
Alex Wade, Alissa Brewer (Stanford)
Stuart Anstis (UCSD)
Subject Mike May
• Blinded by a chemical accident at age 3. • Light sensitive (no form vision) between ages of 3-43
Subject Mike May
Sight restored by a new procedure - Corneal epithelial stem cell replacement
• Resolution• 2 & 3d Form• Motion• Object/Face Recognition
Campbell & Robson (1968)
Spatial frequency (cycles/degree)
Sensitivity
Contrast-Sensitivity Function (CSF)
Resolution limit: 50cpd
Resolution limit < 2 cpd, despite good optics
0 1 2 30
0.5
1
1.5
2
Spatial frequency (c/deg)
Log
sen
siti
vit
y
MM (Post-operatively)Normal
0 1 2 30
0.5
1
1.5
2
Spatial frequency (c/deg)
Log
sen
siti
vit
y MM + 5 monthsMM +11 monthsMM +17 monthsMM +21 monthsCONTROL
No improvement over time
MM could identify simple shapes2D FORM
…but not shapes defined by illusory contours. 2D FORM
2D FORM
Mike can identify simple 2d forms (100% correct)
But “constructive” 2d perception is harder
MM = 80%; controls=100%, 90%, 95%)
MM = 73%; controls = 80%, 85%, 100%
guessing
Letters recognizable
3D FORM
Sensitive (100% correct)to occlusion …
Shading gave no automatic impression of depth:
3D FORM
The circle was seen as a flat disc, with non-uniform surface lightness
“A square with lines attached”
3D FORM
Fails with:
Shape from Shading:
Perspective:
Could NOT recognize a stationary cube from any angle - “square with lines”
MOTION
Couldn’t identify STATIC cube…but with a ROTATING one, “It’s a cube! …going in …going out”
Could NOT recognize a stationary cube from any angle - “square with lines”
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”
MOTION
MOTIONCould make sense of…
Point-light walker
Rotational Glass patterns
Structure from motion(100% correct)
QuickTime™ and aGIF decompressor
are needed to see this picture.
MM = 90%; controls=95%, 80%, 85%).
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!
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”
QuickTime™ and aCinepak decompressor
are needed to see this picture.
GenderMM 70% correctcontrol 100%
Expression (happy/sad/neutral) MM 61% correctcontrol 100%
MM 25% correctcontrol 100%
Poor object & face identification
Clinton&GoreBy Sinha &Poggio
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
Cortical area
Su
rfa
ce a
rea
(cm
2)
0
5
10
15
20
25
30
35
V1(L)
V1(R)
MT+(L)
MT+(R)
control observersMM
Size of V1 and MT+
“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
“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
“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
“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
“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
“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
“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
“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
“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
Images from Ted Adelson
Mike correctly sees thediamonds 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
• 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
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.
Phenomenal Regression to the Real Object
V1
LGN
Parietal (action)
temporal (perception)
The visual process as a causal chain
V1
LGN
Parietal (action)
temporal (perception)
In the normal visual system, each neural representation depends on the later ones.
The visual process as a feedback system
MM was not sensitive to perspective cues
DEPTH
Yet he WAS susceptible to the Muller-Lyer and related illusions
Richard Gregory
“Dumbbell” variant of the Muller-Lyer illusion
Aesthetics
• Color– Variety and vividness were new and impressive
• Bodies– Innate sign stimuli vs. interest based on association
• Dust, waves, fireworks– Meaning confers no aesthetic advantage
Key points about Mike’s perception
• Mike has a severe neural resolution loss,improving slowly if at all.
• He doesn’t see 2D subjective contours.• 2D Geometrical illusions are present.• Both perspective and shape from shading are
ineffective for depth perception.• But motion cues are effective.• Recognizing faces and common objects is a challenge.• We think of Mike as having “the eye of the artist”, inhabiting
a world of abstract 2-dimensional shapes and colors.• This may be why he now uses his vision, as he puts it, “mainly for entertainment”
The End