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

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

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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.

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Asymmetric Attention Control

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Attention Control in Neglect

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Attention theories: Kinsborne

Hemispheric rivalry predicts:Gradients rather then hemifield effects

‘Hyperattention’ on the right (‘magnetism’)

Extinction in the ipsi-lesional side

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Unilateral Neglect

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“Starry Night” test

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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

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Anderson (1996) Salience model

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Attention theories: Posner

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

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Pulvinar

Superior Colliculus

Move

Engage

TPJ

Disengage

Controlling spatial attention beam: Posner

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Posner’s cueing paradigm

**

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Posner’s paradigm - valid cue

*

Fixation

Valid cue

Target

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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.

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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

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ican

Psy

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ogic

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Ass

ocia

tion

. Ada

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.

Cost

Benefit

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Attentional systems (Posner)

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

Vigilance/Alerting System

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New formulation (Corbetta)

Stimulus + Response Selection

Alerting, Sensory Reorienting

Cingulate – Response monitoring, not selection …

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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.

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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

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Representational Theories

Piazza del Duomo effect

Piazza del Duomo effect

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25

מנטלי - ייצוג צד הזנחת

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Is the number larger than…

Increase in RT just to the left of the target number

Vuilleumier et al., 2004

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Gradient of Neglect and Parietal Neurons

Pouget and Driver 2000

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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

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Subtypes of neglect?

Buxbaum et al., 2004

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Role of non-spatial effects

Robertson et al., 1998, Nature

TOJ task:

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Robertson et al., 1998