UNILATERAL NEGLECT MAJOR THEORETICAL ACCOUNTS What could go

UNILATERAL NEGLECT MAJOR THEORETICAL ACCOUNTS

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 S 3 S 110 S 8 S 6 1. 5 1 0. 5 0 RT/midline-RT 2. 5 2 1. 5 1 0. 5 0 -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

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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 100% 600 80% Top tom 1000 Bot LEFT Accuracy RHS Righ t LHS 600 100% 500 80% Control 100% Hits (percent) RT (msec) 450 400 1000 800 600 400 RHS LHS Control -3 -2 -1 80% 100 96 92 88 RHS 84 | 1 2 3 Control LHS -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, Nature 30

Robertson et al. , 1998 31