UNILATERAL NEGLECTMAJOR THEORETICAL

ACCOUNTS

2

What could go wrong after RH damage explaining the contralesional neglect?

Attentional disorders

Spatial representation disorders

Pre-motor representation disorders

3

Attention theories: Heilman

Reduced arousal of right hemisphere

Asymmetry of attention control

Attention to the left side of space is provided exclusively by the right hemisphere whereas Attention to the right side of space is provided by both hemispheres.

4

Asymmetric Attention Control

5

Attention Control in Neglect

6

Attention theories: Kinsborne

Hemispheric rivalry predicts:Gradients rather then hemifield effects

‘Hyperattention’ on the right (‘magnetism’)

Extinction in the ipsi-lesional side

7

Unilateral Neglect

8

“Starry Night” test

9

S110

S6

-3 -2 -1 | 1 2 3

S3

0

0.5

1

1.5

2

2.5

RT/midline-RT

-3 -2 -1 | 1 2 3

S8

0

0.5

1

1.5

2

2.5

RT/midline-RT

Reaction Time - neglect patients

Deouell et al., 2000

10

Anderson (1996) Salience model

11

Attention theories: Posner

Covert shifts of attentionParietal - DisengageSup. Colliculus - MoveThalamus - Engage

12

Pulvinar

Superior Colliculus

Move

Engage

TPJ

Disengage

Controlling spatial attention beam: Posner

13

Posner’s cueing paradigm

**

14

Posner’s paradigm - valid cue

*

Fixation

Valid cue

Target

15

Posner’s paradigm - invalid cue

*

Fixation

Invalid cue

Target

167.42 Fig. 2, Posner et al., “Effects of parietal injury on covert orienting of attention,” The Journal of Neuroscience 4: 1863–1874, (1984). Adapted

with permission of The Society for Neuroscience.

17

Pos

ner,

M.I

., S

nyde

r, C

.R.R

., an

d D

avid

son,

J.,

Att

enti

on a

nd th

e de

tect

ion

of s

igna

ls, J

ourn

al o

f E

xper

imen

tal P

sych

olog

y: G

ener

al 1

09 (

1980

): 1

60–1

74. C

opyr

ight

© 1

980

by th

e A

mer

ican

Psy

chol

ogic

al

Ass

ocia

tion

. Ada

pted

wit

h pe

rmis

sion

.

Cost

Benefit

18

Attentional systems (Posner)

Posterior Attentional System (Orienting)Anterior Att. System (Target Detection)

Vigilance/Alerting System

19

New formulation (Corbetta)

Stimulus + Response Selection

Alerting, Sensory Reorienting

Cingulate – Response monitoring, not selection …

20

Functions of parietal lobes

Dror – Breakdown of connectivity

Adi – IPL and attention theories of neglect

Ronen – The role of the parietal lobes in timing events.

21

Representational Theories

Bisiach - Neglect is a disorder of space representationNeglect is demonstrated in imagery (Piazza effect)If attention is shifted, it is shifted over an internal

representation of space (rather than space itself)Damage to circuits representing segments of

space precludes action towards these segments

22

Representational Theories

Piazza del Duomo effect

Piazza del Duomo effect

24

25

מנטלי - ייצוג צד הזנחת

26

Is the number larger than…

Increase in RT just to the left of the target number

Vuilleumier et al., 2004

27

Gradient of Neglect and Parietal Neurons

Pouget and Driver 2000

28

Reaction Time AccuracyRHS

LHS

Control

600

1000

500

600

400450

80%

100%

80%

100%

80%

100%

-3 -2 -1 | 1 2 384

88

92

96

100

-3 -2 -1 | 1 2 3

400

600

800

1000RHS

LHS

Control RHS

LHSControl

LEFT Right Bottom

Top

RT

(m

sec)

Hits

(p

erc

en

t)

Deouell et al., 2005

29

Subtypes of neglect?

Buxbaum et al., 2004

30

Role of non-spatial effects

Robertson et al., 1998, Nature

TOJ task:

31

Robertson et al., 1998