What could go wrong after RH damage
explaining the contralesional neglect?
Attentional disorders
Spatial representation disorders
Pre-motor representation disorders
2
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.
3
Asymmetric Attention Control
4
Attention Control in Neglect
5
Attention theories: Kinsborne
Hemispheric rivalry predicts:
Gradients rather then hemifield effects
‘Hyperattention’ on the right (‘magnetism’)
Extinction in the ipsi-lesional side
6
Unilateral Neglect
7
“Starry Night” test
8
Reaction Time - neglect patients
RT/midline-RT
2.5
2
S3
S110
S8
S6
1.5
1
0.5
0
RT/midline-RT
2.5
2
1.5
1
0.5
0
-3 -2 -1
|
1
2
3
-3 -2 -1
|
1
2
3
Deouell et al., 2000
9
Anderson (1996) Salience model
10
Attention theories: Posner
Covert shifts of attention
Parietal - Disengage
Sup. Colliculus - Move
Thalamus - Engage
11
Controlling spatial attention beam: Posner
Disengage
Move
TPJ
Superior Colliculus
Pulvinar
Engage
12
Posner’s cueing paradigm
*
*
13
Posner’s paradigm - valid cue
Fixation
Valid cue
*
Target
14
Posner’s paradigm - invalid cue
Fixation
Invalid cue
*
Target
15
7.42 Fig. 2, Posner et al., “Effects of parietal injury on covert orienting of attention,” The Journal of Neuroscience 4: 1863–1874, (1984). Adapted
16
with permission of The Society for Neuroscience.
Benefit
Posner, M.I., Snyder, C.R.R., and Davidson, J., Attention and the detection of signals, Journal of
Experimental Psychology: General 109 (1980): 160–174. Copyright © 1980 by the American Psychological
Association. Adapted with permission.
Cost
17
Attentional systems (Posner)
Anterior Att. System (Target
Posterior Attentional System (Orienting) Detection)
Vigilance/Alerting System
18
New formulation (Corbetta)
Stimulus + Response Selection
Alerting, Sensory Reorienting
Cingulate – Response monitoring, not selection …
19
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.
20
Representational Theories
Bisiach - Neglect is a disorder of space
representation
Neglect 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
21
Representational Theories
Piazza del Duomo effect
22
Piazza del Duomo effect
24
‫הזנחת צד ‪ -‬ייצוג מנטלי‬
‫‪25‬‬
Is the number larger than…
Increase in RT just to the left of the target number
Vuilleumier et al., 2004
26
Gradient of Neglect and Parietal Neurons
Pouget and Driver 2000
27
Reaction Time
Accuracy
RHS
1000
100%
80%
600
LHS
600
100%
500
80%
Control
100%
Hits (percent)
RT (msec)
450
400
1000
800
600
400
RHS
LHS
Control
80%
100
Control
96
LHS
92
88
RHS
84
-3 -2 -1
|
1
2
3
-3
-2
-1
|
1
2
3
28
Deouell et al., 2005
Subtypes of neglect?
Buxbaum et al., 2004
29
Role of non-spatial effects
TOJ task:
Robertson et al., 1998, Nature30
Robertson et al., 1998
31