Lack of sleep Lack of learning in Williams Syndrome

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Lack of sleep- Lack of learning in Williams
Syndrome?
INTERNATIONAL WILLIAMS SYNDROME SYMPOSIUM25th
June 2005, Fonyod
Ilona Kovács, Budapest U. of Technology Gábor
Pogány, Budapest U. of Technology Ákos Fehér,
Rutgers U., USA Petra Kozma, Retina Foundation,
USA
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Reiss et al, J Cog Neurosci volume 12 Suppl 1
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area 17 histometric resultssigns of abnormal
connectivity

• Cell measures differ in peripheral visual
  cortical fields of WS
• Smaller, more tightly packed cells in most layers
  on the left side
• Cell packing density and neuronal size
  differences may be related to visual spatial
  deficits in WS
• Galaburda and
  Bellugi, J Cog Neurosci vol 12 Suppl 1

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Primary visual cortex (V1)

• Local input analysis
• L contrast (1 yr)
• disparity (4 mo)
• motion (2 mo)
• color (2 mo)
• orientation

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Local cortical filters in V1
On multiple scales
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D gt 1 D lt 1
D noise spacing / contour spacing
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(Kovács and Julesz, PNAS, 1993)
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• Contour integration in 3-month-olds
• 60 infants, operant conditioning
• poor contour integration
• lack of global integration (closure)

(Gerhardstein, Kovács, Ditre, Fehér Vision
Research, 2004)
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contour integration card test
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Contour integration in children
(Kovács, Kozma, Fehér, Benedek, PNAS, 1999)
D

• 510 children, 60 adults
• Surprisingly slow curve!!

5-6 y
6-7 y
9-10 y
10-11 y
13-14 y
19-30 y
D noise spacing / contour spacing
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• contour integration in children
• cue specific (no transfer of learning across
  orientation and color)
• visual immaturity
• (not the lack of attention or
  motivation)
• dependent on contour spacing
• limited cortical connectivity?

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limited cortical connectivity in children

• long axonal connections in V1
• Burkhalter et al, 1993 late maturation of V1
  superficial layers horizontal, and V2-V1
  feedback connections in humans

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Reiss et al, J Cog Neurosci volume 12 Suppl 1
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area 17 histometric resultssigns of abnormal
connectivity

• Cell measures differ in peripheral visual
  cortical fields of WMS
• Smaller, more tightly packed cells in most layers
  on the left side
• Cell packing density and neuronal size
  differences may be related to visual spatial
  deficits in WMS
• Galaburda and
  Bellugi, J Cog Neurosci vol 12 Suppl 1

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contour integration in Williams Syndrome

• with
• C. Pleh, A. Lukacs M. Racsmany
• Technical U., Budapest
• P. Kozma
• Rutgers U., NJ

0.6
0.65
0.7
0.75
0.8
0.85
0.9

• poor contour integration
• poor orientation discrimination
• lack of oblique effect

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visual skill (procedural, habit) learning
0 º
11-12º

• shape identification task
• orientation jitter
• 5 practice sessions
• (30 minutes each)

23-24º
with P Kozma, and A Feher Rutgers University
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Day 1. C
Day 1. W
Day 3. C
Day 3. W
Day 5. C
Day 5. W
Day 7. W
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• Basic skill (implicit, procedural) learning
• Time-course of learning (behavioral studies)
• Plastic changes in the brain (imaging)
• behaviorally relevant degree of plasticity is
  retained in the adult mammalian cortex

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• perceptual learning in WS
• abnormalities in the occipital lobe
• sleep disorders
• lack of visual skill learning

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color defined card
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contour integration in 3-month-old babies

• lack of closure superiority
• poor contour integration

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• Professional musicians - a good model to
  investigate plastic changes in the human brain
• Complexity of stimulus
• Extent of exposure
• Two steps
• fast initial phase
• consolidation, and
• gradual increase in
• performance
• Anatomical changes
• Planum temporale
• Anterior corpus callosum
• Primary hand motor and somatosensory
• Cerebellum

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visual development Things start out badly,
then they get better then, after a long time,
they get worse again. (Movshons general law on
visual development, Teller Movshon, 1986)
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visual development should follow the
maturational pattern of participating cortical
structures

• connectivity supporting low-level
• spatial integration is immature
• connectivity supporting the switch
• between perceptual interpretations is
• immature
• top-down connectivity is immature

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visual development Things start out badly, then
they get better then, after a long time, they
get worse again. (Movshons general law on
visual development, Teller Movshon,
1986) Visual development is not a homogeneous
process. It might be possible to map it in terms
of the maturational pattern of cortical
connectivity.
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Stages of myelination
1 mo 2 mo
3-6 mo 7-9 mo gt
9 mo (Knaap and Valk, 1990)
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Growth patterns in the developing brain
(Thompson et al, 2000)
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visual development should follow the
maturational pattern of participating cortical
structures
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• Patient H.J.A. (Humphreys and Riddoch, 1984,
  1987b Riddoch and Humphreys, 1987a)
• posterior cerebral artery stroke
• bilateral lesions of the occipital lobe
  extending anteriorly towards the temporal lobes
• dense visual agnosia
• prosopagnosia
• alexia without agraphia
• achromatopsia
• topographical impairments

MRI (1989) bilateral lesions of inferior
temporal gyrus, lateral occipitotemporal gyrus,
fusiform gyrus, lingual gyrus (Riddoch et al,
Brain, Vol. 122, No. 3, 1999)
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Eric R. Kandel Nobel in 2000 signal
transduction in the nervous system

• Two steps in synaptic plasticity
• short-term memory (protein phosphorylation in
  synapses)
• long-term memory (protein synthesis, which can
  lead to alterations in shape and function of the
  synapse)

The switch from short- to long-term memory
requires gene expression.
(modification of chromatin structure, chromatin
is the DNA-protein complex that constitutes
chromosomes)
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• Switch from short- to long-term memory in humans
• Animal models are limited in terms of stimulus
• complexity and the duration of training.
• Not clear how mechanisms governing synaptic
  plasticity
• at the cellular level are related to the
  flexibility of operations
• seen for large-scale neuronal networks.
• Big questions
• Is there plasticity in the adult brain?
• Are more complex functions relying on
  the same
• mechansims of learning?