Visual development

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• Visual development
• Things start out badly, then they get better
• then, after a long time, they get worst again.
• (Movshons general law on visual development,
  Teller Movshon, 1986)

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Development of human vision Cortical functions

• Low level local processes
• psychophysics, preferential looking
• 2. Integrative processes
• contour integration experiments
• 3. High level processes
• action vs. perception

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• Development of low level local processes

D. Y. Teller, preferential looking
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• contrast sensitivity increasing
• motion 2 mo
• color discrimination 2-4 mo
• stereopsis 4 mo
• (special functions, e.g. face discrimination
  and biological motion)

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Biological motion
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contrast sensitivity increasing motion 2
mo color discrimination 2-4 mo
stereopsis 4 mo (special functions, e.g. face
discrimination and biological motion)
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Contrast sensitivity measurement in the
preferential looking paradigm
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Transfer function
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• Low level local processes
• psychophysics, preferential looking
• 2. Integrative processes
• contour integration experiments
• 3. High level processes
• action vs. perception

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Local cortical filters
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Contour integration task
Contour noise
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D gt 1 D lt 1
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Gestalt
Good continuation
closure
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• 3-month-old babies
• weak contour integration
• lack of closure effect

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contour integration card
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D gt 1 D lt 1
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Contour integration performance in adults and
children
D
5-6 yr
6-7 yr

• slow development

9-10 yr
10-11 yr
13-14 yr
19-30 yr
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• Primary visual cortex (V1)
• Long axonal connections

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• Low level local processes
• psychophysics, preferential looking
• 2. Integrative processes
• contour integration experiments
• 3. High level processes
• action vs. perception

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Thompson, P.M. et al, 2000 Growth pattern of
the developing brain
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Where? (lesion localization problem)
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• Goodale and Milner, 1992
• Dorsal stream (occipitoparietal) ACTION
  computations needed for the manipulation of
  objects.
• Ventral stream (occipitotemporal) PERCEPTION -
  computations needed for object recognition and
  conscious perception.

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• Are the two streams dissociated developmentally?

• The dorsal stream is phylogenetically older
• more genetic preprogramming
• faster maturation
• Ontogenetically
• greater need for early availability of
  exploration
• (dorsal stream)
• The ventral stream is mediating perceptual
  representations that are part of a high-level
  cognitive network enabling us to understand the
  environment. A protracted developmental course
  with plasticity preserved beyond the earliest
  ages would be desirable.
• (extending complexity by extending
  development)

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• Bachevalier et al, 1992 Distler et al, 1996
• delay in the functional maturation of the ventral
  stream in macaques
• object recognition memory (1 vs 2-3 yrs)
• early vs late lesion
• metabolic mapping (3 vs 4 months)

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Development of human vision Cortical functions

• Low level vision, local processes
• Psychophysics, preferential looking (Teller)
• Contrast sensitivity
• 2. Integrative processes
• Contour integration, slow development
• Immature connectivity in V1
• 3. High level processes
• Ungerleider et al Where vs. What
• Goodale et al action vs perception

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