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Cognition & Emotion II > Hemispatial Neglect > Flashcards

Hemispatial Neglect Flashcards

1
Q

LESION

A
  • area of brain damage
  • site of lesion depends on which blood vessel is occluded
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2
Q

CONTRALESIONAL STIMULI

A
  • things occurring on opposite side as lesion
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3
Q

IPSILESIONAL STIMULI

A
  • things occurring on same side as lesion
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4
Q

EXTINCTION

A
  • milder form of neglect only apparent when stimuli occur on both sides of space
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5
Q

STROKE

A
  • when a blood clot breaks off & travels up the artery until it gets caught & blocks blood flow to 1 side of the brain
  • blood flow restricted to 1 half of brain -> neuronal death & eventual fluid-filled cavity (shown in white on MRI scans)
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6
Q

BLOOD VESSELS

A

MIDDLE CEREBRAL ARTERY (MCA)
ANTERIOR CEREBRAL ARTERY (ACA)
POSTERIOR CEREBRAL ARTERY (PCA)

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7
Q

MIDDLE CEREBRAL ARTERY (MCA)

A
  • largest branch of internal carotid
  • supplies:
    1) lateral/inferior frontal lobe
    2) lateral surface of temporal/parietal lobes (incl. primary motor & sensory face/throat/hand/arm areas) & dominant hemisphere (Broca’s area)
    STEIN ET AL. (2007)
  • 51% stroke victims suffer this region
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8
Q

ANTERIOR CEREBRAL ARTERY (ACA)

A
  • supplies:
    1) medial frontal lobes
    2) basal ganglia
    3) primary motor cortex
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9
Q

POSTERIOR CEREBRAL ARTERY (PCA)

A
  • supplies:
    1) temporal lobes
    2) occipital lobes
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10
Q

MCA: CLINICAL STROKE

A
  • contra-lesional hemiparesis (weakness/inability to move opposite side of body/face)
  • contra-lesional hemisensory loss (inability to feel touch on opposite side of face/body)
  • hemianopia (loss of vision on opposite side of space)
  • aphasia (if stroke affects dominant hemisphere for language (left))
  • hemi-spatial neglect
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11
Q

CANCELLATION TESTS

A
  • right hemisphere lesion affects left side of space (vice versa) due to crossed nature of human sensory system
  • aka. patients w/right hemisphere lesions have weakness on left body half & issues noticing things on left side of space
  • cancellation tests = standard for hemispatial neglect; require patient w/right hemisphere lesion to cross out all lines on a page
  • patient will only cross out right-hand side lines
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12
Q

COPYING TESTS

A
  • simply requires patients to copy what they see
  • patients w/hemispatial neglect will ignore all features on left-hand side of picture
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13
Q

RECOGNISING BLINDNESS

A
  • hemispatial neglect isn’t specific to any sense; a patient w/it will have difficulty identifying contra-lesional visual/auditory/tactile stimuli
    EXTINCTION
  • patients can oft detect contra-lesional stimuli BUT not when they occur simultaneously w/ipsilesional stimuli
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14
Q

ACQUIRED BRAIN INJURY: EXTINCTION

A
  • neglect oft resolves into extinction during patient recovery
  • extinction = patient perceives individual touches on left/right side
  • BUT can only perceive right side when presented w/simultaneous touch on both sides
  • same w/visual stimuli; patients can see on either side individually BUT will miss things on contra-lesional side (opposite lesion) when presented together w/things on ipsilesional side (same side)
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15
Q

“BROKEN” NEGLECT

A
  • neglect x extinction = disorder of attention & spatial representation
  • inability to consciously detect/respond to stimuli in contra-lesional side of space
  • manifests as gradient of awareness from ipsilesional -> contralesional > clear divide
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16
Q

NEGLECT: HEMISPHERIC ASYMMETRY

A
  • neglect = more common/persistent in right hemisphere stroke patients (38%) > left hemisphere stoke patients (18%)
  • may reflect right hemisphere dominant system for spatial attention
    HUSAIN & RORDEN (2003)
  • could also be due to presence of additional nonspatial deficits in right hemisphere stroke patients (ie. alertness/sustained attention) that interact w/& exacerbate spatial deficits
17
Q

NEGLECT: NEUROANATOMY

A
  • temporaparietal junction (TPJ) = most common
  • BUT neglect can occur post damage to several regions
18
Q

NEGLECT: ATTENTION SYSTEM PROPERTIES

A
  • revealed several interesting features:
    1) attention can operate in object-centred reference frame
    2) attention can operate on internal representations as well as external stimuli
    3) attention can operate at a late processing stage (extinction severity can be modulated by higher lvl stimuli properties)
    4) attention = competitive process
    5) attention may NOT be a unitary system
19
Q

ATTENTION: OBJECT-BASED

A

MARSHALL & HALLIGAN (1993)
- patient asked to copy flower pics
- 2 flower pic = patient copies right half of each flower > only the flower on the right
- demonstrates that attention operates in object > spatial/frame of reference

20
Q

ATTENTION: INTERNAL REPRESENTATIONS (BISIACH & LUZATTI (1978) EXP I)

A
  • Italian patients w/neglect asked to recall famous landmark in Florence; asked what they can see in minds eye
    RESULTS
  • mostly reported seeing landmarks on good/ipsilateral side to lesion; like they’d lost representation of things on left side both externally/internally
21
Q

ATTENTION: INTERNAL REPRESENTATIONS (BISIACH & LUZATTI (1978) EXP II)

A
  • Italian patients asked to imagine they were standing at opposite square end of Florence
    RESULTS
  • recalled all of previously neglected info; again couldn’t report all contralesional info (though previously recalled correctly)
  • suggests that attention also operates on internal representations (ie. memory/imagination) & external (perception)
22
Q

ATTENTION: LATER PROCESSING (MATTINGLEY ET AL. (1997))

A
  • tested whether attention operates at later processing stage (ie. post low lvl visual processing)
  • presented subjects w/Kaniza figures (removing segment of each circle produces illusion of object in centre); rely on substantial low lvl visual processing (edges/brightness combine -> single illusion)
    RESULTS
  • extinction of left-sided circles = substantially reduced when illusory surface was formed
  • suggests attention operates post low lvl visual processing (even post environmental stimuli being interpreted as objects)
23
Q

ATTENTION: LATER PROCESSING (VUILLEUMIER & SCHWARTZ (2001))

A
  • further evidence for substantial processing of items in contralesional side of space
  • tests pps w/extinction on task; asked simply to identify what they could see from pic set
  • pps presented w/2 pics at a time; either fearful (ie. spiders) OR neutral (ie. ring)
    RESULTS
  • extinction highest in all patients when left stimulus = neutral
  • BUT extinction reduced when left stimulus = fearful
  • suggests that stimulus can break attentional filter despite patient not being aware of info on left side (if info = sufficiently meaningful/important)
24
Q

ATTENTION: LATER PROCESSING (VUILLEIMUER & RAFAL (2000) EXP I)

A
  • evidence that unattended items = processed up to semantic lvl in extinction
  • pps shown 2 same/dif words (ie. one/one or one/two)
    RESULTS
  • higher extinction when words = same aka. meaning of words = processed pre-attentively
  • BUT potential confound = words look similar visually (ie. features); could just be visuals being processed
25
Q

ATTENTION: LATER PROCESSING (VUILLEIMUER & RAFAL (2000) EXP II)

A
  • showed pps words that looked dif BUT w/either same semantic meaning (ie. one/1) or dif meaning (ie. one/2)
    RESULTS
  • neglect = still lower for words w/same meaning even if they looked dif > words w/dif meanings
  • aka. NOT low lvl visual features of words that drive dif but semantic meaning
26
Q

ATTENTION: LATER PROCESSING

A
  • info processed pre-attentively (prior to attention/awareness) includes:
    1) task-relevance of stimuli (response related info)
    2) integration of features into whole objects/shapes
    3) emotional stimuli significance
    4) semantic info
27
Q

ATTENTION: COMPETITION (POSNER ET AL. (2014))

A
  • evidence that neglect involves deficit disengaging from ipsilesional stimuli
  • reflexive attention = also studies w/Posner cueing paradigm BUT pps = cued exogenously here
  • aka. light flash/something attention grabbing occurs in peripheral location
  • target appears in flash location (cued trial)/ other (uncued trial)
    RESULTS
  • RTs = ^ for uncued contra condition
  • indicates issue disengaging attention from cues on ipsilesional side
28
Q

ATTENTION: NOT A UNITARY SYSTEM (VERDON ET AL. (2010) PROCEDURE)

A
  • neuroanatomy of hemispatial neglect & functional components using voxel-based lesion-symptom mapping
  • attempted to map specific symptoms onto lesion locations; 80 patients w/left neglect due to right hemisphere lesions tested on range of standard neuropsychological tests
  • factor analysis used to break down symptoms into coherent profiles of co-varying deficits
29
Q

ATTENTION: NOT A UNITARY SYSTEM (VERDON ET AL. (2010) RESULTS)

A
  • 3 distinct components identified:
    INFERIOR PARIETAL
    1) perceptive/visuo-spatial neglect
  • left side omissions on word/text reading
  • bias on line bisection
    DORSOLATEAL PREFRONTAL CORTEX
    2) exploratory/visuo-motor performance
  • missing left space side in cancellation tasks
    TEMPORAL LOBE
    3) object-centred neglect
  • missing left word side in compound reading
  • missing left object side in Ota search task
30
Q

SUMMARY

A
  • neglect may be a syndrome/condition characterised by set of associated symptoms (some dissociable) rather than unitary attention disorder
  • attention may be collection of associated functions mediated by connected by anatomically separate brain regions; may be system for resolving competition at dif brain lvls:
    1) sensory input
    2) simple visual features/objects/semantics/emotion
    3) sensory inputs for awareness/response

Cognition & Emotion II (15 decks)

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