Neglect

Question 1

Tasks used to assess neglect

Answer 1

Line bisection
Cancellation
Drawing - figure copying vs from memory
Extinction
Chimeric faces

Question 2

Vallar & Perani; Vallar 2001

Answer 2

Right IPL most typically damaged

Question 3

Karnath 2001; 2004

Answer 3

Superior temporal cortex most commonly damaged

Question 4

Karnath 2011

Answer 4

3 areas: IPL/TPJ, superior/middle temporal cortex and ventrolateral PFC.
All connected by dense perisylvian network of fibres.
= form system responsible for spatial orienting and attention.
Damage to any of 3 areas or white matter tracts could cause neglect = disconnection syndrome.

Question 5

DeSchotten 2005

Answer 5

Intraoperative electrical stimulation revealed superior occipito-frontal fasciculus (fronto-parietal pathway) was most responsible for symmetrical processing of a visual scene.
= further evidence for role of white matter connections.

Question 6

Karnath 2009

Answer 6

Damage to right perisylvian network tracts can predict neglect.
Also strokes that damage subcortical areas e.g. basal ganglia can cause abnormal perfusion of cortical areas in perisylvian network and cause neglect.

Question 7

Itti & Koch (2001)

Answer 7

Computational model of visual attention.
Dorsal stream in PPC used for orienting attention, making saccades, “bottom-up” so responds to unexpected/relevant stimuli.
Monkey with LIP lesion can’t visualise object in space/reach for it.
Ventral stream = explicit object recognition, top-down so can influence control

Question 8

Corbetta & Shulman 2011; 2002

Answer 8

Dorsal stream = IPS, SPL, FEF. Top-down orienting of attention, makes saccades etc.
Ventral = IPL, STG, TPJ, IFG. Shifts attention and acts as bottom-up “circuit breaker” (with aid of LC).
Argue anatomical nature of neglect better fits their theory of dysfunction in TPJ-VLPFC mainly, as STG is most common lesion site (also right ventral PFC if frontal lesions are involved).
Also dorsal IPS-FEF system is bilateral (orients attention across both hemifields) while TPJ-VLPFC is lateralised to right hemisphere, which mirrors nature of neglect.
Neglect patients more impaired by stimulus detection, rather than top-down orienting - shown by fact they can be cued to attention to location (Riddoch & Humphreys 1983; Karnath 1988)
But many neglect patients have trouble initiating contralateral hand/eye movements (Mattingley 1998) done by dorsal IPS-FEF system - why? Suggest dysfunction in dorsal stream stems from damage to ventral TPJ-VLPFC system, e.g. from reduced input from TPJ. “Functionally inactivated”. Would explain refixating of saccades (Husain 2001)

Question 9

Weiss 2000

Answer 9

fMRI and line bisection task.
Pen and paper i.e. near/personal space = dorsal visuomotor processing.
Laser pointer and pen i.e. far/extrapersonal space = more ventral, visuoperceptual processing.

Question 10

Hillis 2006

Answer 10

Viewer-centred = damage to right angular gyrus of parietal lobe.
Object-centred = damage to superior temporal gyrus.

Question 11

Verdon 2009

Answer 11

Voxel-based lesion mapping.
Perceptual/visuospatial tasks = posterior parietal (IPL) lesions.
Exploratory/visuomotor tasks = more anterior / frontal lesions e.g. DLPFC.

Question 12

Weschler blocks

Answer 12

Split brain patients show RH is dominant for certain visuospatial tasks (could do task with left but not right hand).

Question 13

Lausberg (2003)

Answer 13

Split brain patients showed LH was impaired at using whole of personal space for motor gestures with contralateral hand. Suggests LH can’t compute spatial coordinates as well as RH.

Question 14

Bisiach & Luzzatti (1978)

Answer 14

Duomo di Milano: perceptual vs representational space.
Double dissociatio between space that is perceptual and egocentric vs allocentric, long-term memory representation.
= attention, not memory or perceptual.

Question 15

Della Sala (2010)

Answer 15

Representational neglect results from short-term visuospatial working memory ability, not impairment to long-term memory stores.

Question 16

O’Keefe & Nadel 1978

Answer 16

Rat place cells in HC

Question 17

Morris 1982

Answer 17

Morris water maze. Rats with HC lesions = impaired

Question 18

Maguire 2006

Answer 18

London taxi drivers = larger right HC

Question 19

Rossetti 1998

Answer 19

Prism lens glasses = long-term improvement.

Supports Karnath’s (1998) eye gaze experiments.

Question 20

Karnath 1998

Answer 20

Spatial frame of reference shifted: exploratory eye gaze patterns deviate round central point as normal, just centre is shifted to right.
Altered neural representation of space.

Question 21

Kinsbourne 1987

Answer 21

Damage to RH = LH becomes overactive.

Question 22

Cazzoli 2012

Answer 22

TMS over LH = improves neglect.

Gives support to view LH is now overactive (Kinsbourne) and balances attention again (Duncan hypothesis)

Question 23

Duncan 1998

Answer 23

Competition Bias theory

Question 24

Pedroli 2015

Answer 24

VR now used. Can engage motor skills too, but safe.

Role for learning and memory? Can LH learn to interact with left hemifield more?

Question 25

Corbetta 2005

Answer 25

Restore attentional imbalance (LH overactive) = recovery from neglect

Question 26

Umarova 2011

Answer 26

LH hyperactivity can occur after right hemisphere damage but no neglect = secondary symptom instead of cause? Neglect showed reduced fMRI activation in right parietal and lateral occipital cortex.

Question 27

Lunven & Bartolomeo 2017

Answer 27

Neglect typically thought to involve damage to IPL, although IFG and STG implicated too. Recent research emphasised role of superior longitudinal fasciculus (frontoparietal pathway) and interhemispheric connections (so disconnection syndrome). If hemispheres can't communicate, LH can't compensate for RH damage - amount of interhemispheric communication may predict severity of neglect, particularly connections between posterior parietal and occipital cortex.

Question 28

Husain 2001

Answer 28

Area of monkey PPC which activate when saccading to remembered locations (Mazzoni 1996). Damage to right parietal cortex = refixating targets, treating old targets as novel. = Spatial working memory deficit

Question 29

Duncan 1998

Answer 29

Biased Competition Theory. Neglect due to lateral attentional imbalance caused by unilateral damage to RH so LH wins, evidenced by extinction, particularly double simultaneous stimulation (DSS).

Question 30

Ladavas 2015

Answer 30

a-tDCS over right parietal cortex boosted effect of prism adaptation treatment and therefore symptoms of neglect.

Question 31

Pedroli 2015

Answer 31

VR allows patients to interact with ecological, dynamically changing environment involving changes in attention to things in personal and extrapersonal space (not just 2D pen and paper).

Question 32

Tanaka 2010

Answer 32

VR: moving cues in left hemifield increased visual attention to left.

Question 33

Rossetti (1998)

Answer 33

Prism lens glasses shift visual field to right (shift frame of reference) = long-lasting changes. Gives weight to Karnath (1998) eye gaze experiments.

Question 34

Cazzoli (2012)

Answer 34

TMS to overactive LH improved symptoms, long-lasting. Gives weight to theories suggesting LH is overactive/attentional imbias etc