Transcript Slide 1

Fundamentals of Neuroscience
Unilateral Neglect (Lec 01)
James Danckert PAS 4040 [email protected]
Web page for slides
http://www.arts.uwaterloo.ca/~jdancker/Fundamentals_2003/fund_index.htm
Unilateral Neglect
• failure to respond to or attend to
contralesional stimuli
• usually a result of right parietal lesions
– current controversy whether the inferior
parietal lobe or the superior temporal gyrus is
the critical lesion site for neglect
Critical lesion
• Vallar – inferior
parietal lobe
(based on CT
scans)
• Karnath, et al. –
superior
temporal gyrus
(based on MRI)
Regardless of who is right – the lesion is in tertiary association cortex –
integration of multiple sensory signals and extensive connections with frontal areas.
Anton Raederscheidt
Unilateral Neglect
• most commonly observed for the visual
modality (so often called visual neglect)
• can have multimodal neglect – auditory
and tactile neglect most common
• can occur following left parietal lesions –
usually less severe and recovers more
frequently
Clinical tests of neglect – cancellation tasks.
Star cancellation
Albert’s lines
Clinical tests of neglect – line bisection.
patient’s midline
Clinical tests of neglect – line bisection.
left
Schenkenberg et al. 1980
centre
right
Clinical Tests of Neglect – figure copying
Clinical Tests of Neglect – free drawing
Show video?
Neglect
• Neglect is not a disorder of vision or memory per se
– even when asked to imagine scenes the patient
neglects the left – and this is viewpoint dependent
Neglect and Imagery
• Map of France test.
Spatial vs. Object based neglect.
Chimaeric Faces
• Healthy controls
prefer faces smiling
on left (Q reading
bias?)
• Neglect patients
prefer faces smiling
on right – even
though they “see” the
whole face
Which one is happier?
Spatial vs. Object based neglect.
• Axis-based neglect
Spatial vs. Object based neglect.
• Figure – Ground Segregation
Spatial vs. Object based neglect.
• Behrman and Tipper, 1994 – strongest evidence for object
based neglect.
Neglect and Extinction
• Double simultaneous stimulation (DSS) – two stimuli (targets)
presented simultaneously to the left and right of the patient’s
midline – left target typically “extinguished”
single left
single right
DSS trial
Object based effects on extinction.
• Gestalt Principles – visual occlusion
Temporal components of Neglect
• Temporal Order Judgement (TOJ) task
Which came first?
Temporal components of Neglect
• Phasic Alerting – arousal levels important in neglect too!
Temporal components of Neglect
• Attentional Blink task – Hussain et al. Nature,
1997
C
3
M
TARGET 2
7
H
TARGET 1
T1
T2
180 360 540 720
…
1800
stimulus onset asynchrony (SOA)
Temporal components of Neglect
100
• Attentional Blink task – Hussain et al. Nature,
1997
50
single task
neglect patients
100
dual task
0
180
360
540
720
900
1080
1260
% correct
% correct
healthy controls
1440
1620
1800
50
single task
dual task
0
180
360
540
720
900
1080
1260
1440
1620
1800
Break 1
What happens to neglected information?
The Burning House example.
Which house would you prefer to live
in?
A. The top one.
Why?
A. Roomier, especially in the attic.
Implicit Processing in Neglect – illusions.
• Line bisection in the Judd and Muller-Lyer
illusions
Illusions and extinction
• improvement of extinction for illusory figures
illusory square
no illusory square
• when asked “how many objects did you see?” less
extinction was observed for illusory figures
Neglect and Extinction
• Double simultaneous stimulation (DSS) – two stimuli (targets)
presented simultaneously to the left and right of the patient’s
midline – left target typically “extinguished”
single left
single right
DSS trial
Object specific
extinction
• Target specific –
two forks lead to
greater extinction
than a fork and a
key (Rafal, 1996).
Unconscious activation in extinction
• right striate and extrastriate regions
activated for extinguished stimuli
Rees et al. 2000 Brain
What happens to neglected information?
The Burning House.
What would happen if a different
question was asked?
Which house is warmer?
Implicit processing in neglect using
the Flanker Task
OE
Colour flanker
Letter flanker
RT
Unidimensional Stimuli.
c
n
i
Colour and form processing in blindsight
using the flanker task.
flankers in sighted field
OO
congruent
EO
incongruent
flankers in blind field
OO
congruent
OE
incongruent
Blindsight patient AG – occipital lesion.
L
R
Letter flankers
1100
1100
1050
1050
1000
1000
RT
RT
Colour flankers
950
950
900
900
850
850
800
800
C
I
sighted
C
I
blind
C
I
sighted
C
I
blind
Implicit Processing in Neglect – flanker task.
• Neglected flankers are nevertheless processed (Danckert et
al. 1999)
JS
star
cancellation
(LVF/RVF)
letter
cancellation
(LVF/RVF)
line
bisection
4 / 25
0 / 14
+ 43.3
simple
detection
(LVF/RVF)
0 / 100
Patient JS - Unidimensional flanker performance.
mean VRT (msec)
neglected flankers
perceived flankers
800
750
53 msec
700
650
cong
incong
73 msec
cong
incong
The Flanker Task: Bidimensional Stimuli.
identify colour
identify letter
EE
double congruence
(CD)
EE
OE
single congruence
(CS)
EE
EE
OE
single incongruence
(IS)
double incongruence
(ID)
OE
OE
data driven
EE
OE
goal driven
EE
OE
Goal-driven selection is dominant.
REACTION TIME (msecs)
480
n.s.
470
COLOUR
LETTER
460
n.s.
450
440
430
420
IDENTIFY
LETTER
IDENTIFY
COLOUR
E E
E E
CD
E E
E O
CS
E O
E O
E E
E O
IS
ID
Patient JS - Bidimensional flanker performance.
perceived flankers
neglected flankers
800
name letter
780
median VRT (msec)
760
740
720
700
680
660
640
name colour
620
600
CD
CS
IS
ID
E E OE E E OE
CD
CS
IS
ID
E E E E OE OE
What happens to neglected information?
Top-down – goals can influence how the information is processed
Bottom-up – information is still processed in extrastriate visual cortex
All of this is despite a lack of awareness!
Motor control in Neglect
• Line bisection in different regions of space
• Pointing to targets
• TOJ pointing
• Motor imagery
Clinical hints
• cancellation tasks
Line bisection in near and far space
• Altitudinal neglect
neglect of near space
neglect of lower visual field
Line bisection in near and far space
• PET in normals – line bisection in near and far space
Intraparietal
Ventral frontal
NEAR SPACE
Ventral occipital
FAR SPACE
Weis et al. Brain, 2000
Pointing to targets
• Pointing and bisecting
LEDS
Goodale et al. Can J Psych, 1990
Pointing to targets
• Pointing and bisecting LEDS
bisection errors
Goodale et al. Can J Psych, 1990
Pointing to targets
Goodale et al. Can J Psych, 1990
Temporal order pointing in patient PB
(neglect).
• Point to which target appeared first.
Patient PB - left target
(incorrect first response)
250
y - position (mm)
200
150
100
50
0
-50
50
100
150
-50
x - position (mm)
200
250
Speed accuracy trade offs.
left to right
near to far
Velocity profiles in Patient LR (neglect).
velocity (cm/sec)
• Higher peak velocity for rightward movements of
either hand
• Longer deceleration periods for leftward and near
movements of either hand.
R
200
L
R
L
R
L
R
L
6
time (sec)
8
R
L
100
velocity (cm/sec)
0
0
2
4
10
12
Motor Imagery
Movement duration for the VGPT
3.9
movement duration (sec)
3.7
imagined
movements
3.5
3.3
3.1
actual
movements
2.9
2.7
2.5
30
14.9
7.5
target width (mm)
3.7
1.9
Patient LR – Contralesional hand (L)
18
16
real movements
14
12
10
movement duration (sec)
8
6
4
imagined movements
30
14.9
7.5
3.7
1.9
target width (mm)
13
12
real movements
11
10
9
8
imagined movements
7
6
5
30
14.9
7.5
target width (mm)
3.7
1.9
Patient LR – Ipsilesional hand (R)
15
14
real movements
13
12
11
10
movement duration (sec)
9
imagined movements
8
7
6
30
14.9
7.5
3.7
1.9
3.7
1.9
target width (mm)
9
8.5
imagined movements
8
7.5
7
6.5
6
5.5
real movements
5
4.5
4
30
14.9
7.5
target width (mm)
Was the poor relationship between real and imagined
movements for LR due to a loss of visual and/or
proprioceptive feedback of the moving hand?
view target for 2 sec
perform movements while imagining
the previously viewed target
Control subject MR
movement duration (sec)
5
4.5
real movements
4
3.5
3
imagined movements
2.5
2
30
14.9
7.5
3.7
1.9
target width (mm)
movement duration (sec)
5
imagined targets
4.5
4
3.5
3
imagined movements
2.5
2
30
14.9
7.5
target width (mm)
3.7
1.9
Patient LR
Imagining the target vs. imagining the whole movement.
7.1
imagined targets
duration (secs)
6.9
6.5
6.1
imagined movements
5.5
30
14.9
7.5
target width (mm)
3.7
1.9
Pointing without vision of the hand.
6.5
6
real movements
(with vision of hand)
duration (sec)
5.5
imagined movements
5
4.5
real movements
(without vision of hand)
4
3.5
3
30
14.9
7.5
target width (mm)
3.7
1.9
Motor control in Neglect
• Path curvature is controversial – difficulty replicating
• Role in spatial components of movements relatively
uncontroversial
• Probably controls the spatial component of movements
of both limbs
• TMS and fMRI data suggesting right FEF important for
saccades to both contralateral and ipsilateral space
• PET and fMRI suggests right parietal important for covert
attention (in all regions of space?)
• Fronto-parietal patient with a specific remapping deficit
(Colby et al. 1992)
Spatial re-mapping – retinal co-ordinates
Spatial re-mapping – updated representation.
Saccadic Dysmetria
• Patient with a fronto-parietal lesion can’t do the double-step
saccade task when first saccade is contralesional
Saccadic Dysmetria
• No problem with visually guided saccades (targets presented for
500 msec)
contra move first
contra move second
Saccadic Dysmetria
• Errors come when both targets are presented before the first eye
movement begins (targets presented in less than 180 msec)
contra move first
contra move second
Break 2
Rehabilitation of Neglect
•
•
•
•
Caloric stimulation
Neck muscle vibration
Restriction of the ipsilateral limb
Prism Adaptation
Prism Adaptation – Rossetti and colleagues
• prisms shift world
further to the right
(into the patient’s
‘good’ field)
• patient’s
movements
compensate for the
prismatic shift – in
the opposite
direction
• after effects lead to
better processing of
previously
neglected stimuli
Prism Adaptation – Rossetti and colleagues
• effects of prism
adaptation not restricted
to adapted hand or eye
• visual imagery, postural
balance also affected
• after effects most
prominent 2 hours after
adaptation and can last
for weeks – not so for
controls for whom effects
are absent after only a
few trials
Prism adaptation – is neglect really
ameliorated?
• patient LR showed classic neglect bias on
chimaeric faces test
• eye movement pattern also showed
neglect
Patient LR – chimaeric faces.
Which one is happier? Top or bottom?
Controls – bias towards left smiling face
Neglect – bias towards right smiling face
Perceptual task.
• 6 different pairs of faces
• top and bottom smiling faces and left and right sided smiling
faces randomised across trials
• 3 different durations of stimulus – 500, 1000 and 1500 msec
Eye movement task.
• 18 different faces presented individually
• simply explore the full extent of the faces
• 6 of the 18 faces were chimaeric ‘probes’
• durations of stimuli –10 sec
Prism adaptation for LR.
Subjective judgment of straight ahead.
Eye movements to chimaeric faces controls.
LR’s eye movements pre and post.
PRE
POST
Eye movements pre and post.
PRE
POST
Ferber, Danckert, Joanisse, Goltz & Goodale 2002 Neurology (in press)
Perception pre and post.
• On 96% of trials LR chose the right-smiling face to be the
happier one.
• When asked if he noticed anything unusual about the
faces stimuli he said he thought one of them needed a
shave!
• Even at the longest durations (and even for the 10 sec
duration for chimaeric faces in the eye movement task) LR
was unaware that the faces were chimaeric.
Prism adaptation did not alter LR’s
awareness of the chimaeric faces!
Prism adaptation – is neglect really
ameliorated?
• after prism adaptation LR’s eye movements now
fully explored the faces
• despite a dramatic change in the pattern of eye
movements he still chose the right sided happy
faces on 92% or trials
• more importantly, he was unaware that the
chimaeric faces were unusual in any way – his
only comment regarding the faces was that “one
of them needs a shave!”
Ferber, Danckert, Joanisse, Goltz, & Goodale, in press, Neurology
Mechanisms of Neglect
• Why is neglect more common after right
parietal lesions?
– Kinsbourne – attentional asymmetry (global
vs. local)
– Ferber – spatial working memory
– Goldberg – novelty seeking?
– Danckert – some combination of all three?
Object-based neglect is still puzzling!
Attentional Hypotheses
• inattention
– unaware of left stimuli (cuing can correct this)
• ipsilesional bias
– each hemisphere orients contralaterally and inhibits
orienting of the opposite hemisphere
– hyper vs. hypo orienting – why is neglect more
common from right parietal lesions?
– ipsilesional bias vs. reduced contralesional capacity?
• disengage deficit
– ipsilesional cues led to longer RTs to contralesional
targets (contra cues with ipsi targets were not affected
as much)
• reduced sequential attentional capacity
– neglect of centre!
Motor Intention
• patients may be aware of stimuli but may fail to act
– reduced capacity vs. ipsilesional bias
A
E
• exploration deficits – searching by touch or eyes
• Bisiach’s pulley system
congruent movement
incongruent movement
Other factors to consider
• Spatial working memory
– our neglect patient showed a SWM deficit for vertically arranged
stimuli
– if it doesn’t get into SWM (or processes of SWM are deficient –
more limited than usual) then it won’t make it into awareness
• Novelty vs. familiarity
– if the right hemisphere is dedicated to novelty seeking
behaviours (exploratory eye movements are one good example)
then a deficit in this capacity would lead to poor allocation of
attention across the whole visual field (does left hemispehere
cover the RVF deficit in neglect?)
• Mutual Exclusivity –who needs it?
Introducing the Neglect Syndromes
extinction
(superior parietal –
but what about simultanagnosia
and optic ataxia?)
motor neglect
(fronto-parietal lesions)
pure neglect
(inferior parietal or
STG for the true connoisseur!)
Neglect and anosagnosia
• anosagnosia – denial or unawareness of
impairment (even extends to inanimate
objects!)
• caloric stimulation ameliorates
anosagnosia temporarily
• difference between insight and
anosagnosia
• knowing “what” (or “that something is so”)
vs. knowing “how” or “why”
Neglect and consciousness
• What does neglect tell us about the neural
correlates of consciousness?
• Does the brain really represent objects in
halves?
• Can’t simply be an exploration deficit.
• Some complex interaction between
working memory, temporal processing,
body schemas, actions/intentions, etc.?
Acknowledgements
Flanker tasks in neglect and blindsight
Motor imagery in neglect
Paul Maruff
Glynda Kinsella
Steven de Graaff
Jon Currie
Murat Yucel
Carly Ymer
Susanne Ferber
Mel Goodale
Timothy Doherty
Prisms in neglect
Motor control in neglect
Susanne Ferber
Herb Goltz
Marc Joanisse
Mel Goodale
Yves Rossetti
Susanne Ferber
Mel Goodale
Haitao Yang
End of Lecture