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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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slide1

Vision after complete blindness: Mike May

Fine et al., Nature Neuroscience 2003; Robert Kurzon, ‘Crashing Through’

slide2

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

ione fine ucsd usc1

Ione Fine (UCSD USC)

Geoff Boynton (UCSD/Salk): fMRI+

ione fine ucsd usc2

Ione Fine (UCSD USC)

Brian Wandell (Stanford)

and

Alex Wade, Alissa Brewer (Stanford)

Geoff Boynton (UCSD/Salk): fMRI+

ione fine ucsd usc3

Ione Fine (UCSD USC)

Brian Wandell (Stanford)

Alex Wade, Alissa Brewer (Stanford)

Geoff Boynton (UCSD/Salk): fMRI+

Stuart Anstis (UCSD)

slide8

Subject Mike May

  • Blinded by a chemical accident at age 3.
  • Light sensitive (no form vision) between ages of 3-43
slide9

Subject Mike May

  • Sight restored by a new procedure -
  • Corneal epithelial stem cell replacement
slide11

Resolution

  • 2 & 3d Form
  • Motion
  • Object/Face Recognition
slide12

Contrast-Sensitivity Function (CSF)

Sensitivity

Spatial frequency (cycles/degree)

Campbell & Robson (1968)

Resolution limit: 50cpd

slide13

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)

slide14

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)

slide15

2D FORM

MM could identify simple shapes

slide16

2D FORM

…but not shapes defined by illusory contours.

slide17

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

slide18

3D FORM

Sensitive (100% correct)

to occlusion …

slide19

3D FORM

Shading gave no automatic impression of depth:

The circle was seen as a flat disc, with non-uniform surface lightness

slide20

3D FORM

Fails with:

Shape from Shading:

Perspective:

“A square with lines attached”

slide21

MOTION

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

slide22

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

slide23

MOTION

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

slide24

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”

slide25

MOTION

Could make sense of…

Point-light walker

Rotational Glass patterns

Structure from motion

(100% correct)

MM = 90%;

controls=95%, 80%, 85%).

slide27

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!
slide28

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”

slide29

Poor object & face identification

MM 25% correct

control 100%

Gender

MM 70% correctcontrol 100%

Expression (happy/sad/neutral)

MM 61% correct

control 100%

slide30

Clinton&Gore

By

Sinha &Poggio

slide32

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

slide33

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

slide34

“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

slide35

“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

slide36

“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

slide37

“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

slide38

“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

slide39

“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

slide40

“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

slide41

“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

slide42

“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

slide43

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

phenomenal regression to the real object
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
phenomenal regression to the real object1
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.
slide46

The visual process as a causal chain

Parietal (action)

temporal (perception)

V1

LGN

slide47

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.

slide48

MM was not sensitive to perspective cues

Yet he WAS susceptible to the Muller-Lyer and related illusions

DEPTH

aesthetics
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
slide52

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”