Lack of sleep- Lack of learning in Williams Syndrome?

INTERNATIONAL WILLIAMS SYNDROME SYMPOSIUM25th June 2005, Fonyod

Department of Cognitive Science

Budapest University of Technologyand Economics

Ilona Kovács, Budapest U. of TechnologyGábor Pogány, Budapest U. of TechnologyÁkos Fehér, Rutgers U., USAPetra Kozma, Retina Foundation, USA

Reiss et al, J Cog Neurosci volume 12 Suppl 1

area 17 histometric results:signs 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

Primary visual cortex (V1)

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

newborn 1mo 2 mo 3 mo 6 mo adult

Teller, 1997

Campbell-Robson CSF Chart

Local cortical filters in V1

On multiple scales

D > 1 D < 1

D = noise spacing / contour spacing

(Kovács and Julesz, PNAS, 1993)

Contour integration in 3-month-olds:

• 60 infants, operant conditioning• poor contour integration• lack of global integration (closure)

(Gerhardstein, Kovács, Ditre, FehérVision Research, 2004)

contour integration card test

0.6 0.65 0.7 0.75 0.8 0.85 0.9

Contour integration in children

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

5-6 y

6-7 y

9-10 y10-11 y

13-14 y

19-30 y

D(Kovács, Kozma, Fehér, Benedek, PNAS, 1999)

D = noise spacing / contour spacing

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?

• long axonal connections in V1• Burkhalter et al, , 1993: late maturation of V1 superficial layers

horizontal, and V2-V1 feedback connections in humans

limited cortical connectivity in children

Reiss et al, J Cog Neurosci volume 12 Suppl 1

area 17 histometric results:signs 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

contour integration in Williams Syndrome

with

C. Pleh, A. Lukacs M. Racsmany

Technical U., Budapest

P. KozmaRutgers U., NJ

0.6 0.65 0.7 0.75 0.8 0.85 0.9

6 yr7 yr

10 yr

11 yr

14 yr

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

0 º

23-24º

11-12º

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

visual skill (‘procedural,’ ‘habit’) learning

with P Kozma, and A FeherRutgers University

Groups Mean age Total testing time

Sleep

1. (n=8) 24,5 3,5 hours no

2. (n=8) 29,75 10 hours no

3. (n=8) 28,75 5 days yes

group 1.

-1

-0.5

0

0.5

1

1.5

2

2.5

3

1. 2. 3. 4. 5.practice session (total time 3.5 hours)

Th

res

ho

ld c

ha

ng

e

(de

gs

)

group 2.

-1-0.5

00.5

11.5

22.5

3

1. 2. 3. 4. 5.practice session (total time 10 h)

Th

res

ho

ld c

ha

ng

e

(de

gs

)

group 3.

-1-0.50

0.51

1.52

2.53

1. 2. 3. 4. 5.

practice session (total time: 5 days)

Th

res

ho

ld c

ha

ng

e

(de

gs

)

-10

-5

0

5

10

15

20

1. 2. 3. 4. 5.

practice session

% t

hre

sho

ld c

han

ge

1.csoport

2.csoport

3.csoport

Perceptual learning (WS/Control)

4550556065707580859095

100

0 1 2 3 4

level of difficulty

% c

orre

ct

1. nap K

1.nap W

3. nap K

3.nap W

5. nap K

5. nap W

7.nap W

Day 3. C

Day 1. C

Day 5. C

Day 3. W

Day 1. W

Day 5. WDay 7. W

Texture discrimination task

Karni & Sagi 1991:

• specific to quadrant• specific to horizontal background bars• specific to eye• slow improvement• sleep-dependent

Scwartz et al, 2002:

• fMRI; training-dependent monocular increases (V1)

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

perceptual learning in WS

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

color defined card

• lack of closure superiority

• poor contour integration

contour integration in 3-month-old babies

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

visual development

“Things start out badly, then they get better;then, after a long time, they get worse again.”

(Movshon’s general law on visual development, Teller & Movshon, 1986)

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 immatureis immature

visual development

“Things start out badly, then they get better;then, after a long time, they get worse again.” (Movshon’s 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.

1 mo 2 mo 3-6 mo 7-9 mo > 9 mo

(Knaap and Valk, 1990)

Stages of myelination

(Thompson et al, 2000)

Growth patterns in the developing brain

visual development: should follow the maturational pattern of participating cortical structures

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)

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)

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?