Neglect Flashcards
Tasks used to assess neglect
Line bisection Cancellation Drawing - figure copying vs from memory Extinction Chimeric faces
Vallar & Perani; Vallar 2001
Right IPL most typically damaged
Karnath 2001; 2004
Superior temporal cortex most commonly damaged
Karnath 2011
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.
DeSchotten 2005
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.
Karnath 2009
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.
Itti & Koch (2001)
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
Corbetta & Shulman 2011; 2002
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)
Weiss 2000
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.
Hillis 2006
Viewer-centred = damage to right angular gyrus of parietal lobe. Object-centred = damage to superior temporal gyrus.
Verdon 2009
Voxel-based lesion mapping.
Perceptual/visuospatial tasks = posterior parietal (IPL) lesions.
Exploratory/visuomotor tasks = more anterior / frontal lesions e.g. DLPFC.
Weschler blocks
Split brain patients show RH is dominant for certain visuospatial tasks (could do task with left but not right hand).
Lausberg (2003)
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.
Bisiach & Luzzatti (1978)
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.
Della Sala (2010)
Representational neglect results from short-term visuospatial working memory ability, not impairment to long-term memory stores.
O’Keefe & Nadel 1978
Rat place cells in HC
Morris 1982
Morris water maze. Rats with HC lesions = impaired
Maguire 2006
London taxi drivers = larger right HC
Rossetti 1998
Prism lens glasses = long-term improvement.
Supports Karnath’s (1998) eye gaze experiments.
Karnath 1998
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.
Kinsbourne 1987
Damage to RH = LH becomes overactive.
Cazzoli 2012
TMS over LH = improves neglect.
Gives support to view LH is now overactive (Kinsbourne) and balances attention again (Duncan hypothesis)
Duncan 1998
Competition Bias theory
Pedroli 2015
VR now used. Can engage motor skills too, but safe.
Role for learning and memory? Can LH learn to interact with left hemifield more?
Corbetta 2005
Restore attentional imbalance (LH overactive) = recovery from neglect
Umarova 2011
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.
Lunven & Bartolomeo 2017
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.
Husain 2001
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
Duncan 1998
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).
Ladavas 2015
a-tDCS over right parietal cortex boosted effect of prism adaptation treatment and therefore symptoms of neglect.
Pedroli 2015
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).
Tanaka 2010
VR: moving cues in left hemifield increased visual attention to left.
Rossetti (1998)
Prism lens glasses shift visual field to right (shift frame of reference) = long-lasting changes. Gives weight to Karnath (1998) eye gaze experiments.
Cazzoli (2012)
TMS to overactive LH improved symptoms, long-lasting. Gives weight to theories suggesting LH is overactive/attentional imbias etc
