1. Fundamentals of Neuroscience Unilateral Neglect (Lec 01)
James Danckert PAS 4040
Web page for slides

2. 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

3. 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.

4. Anton Raederscheidt

5. 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

6. Clinical tests of neglect – cancellation tasks.
Star cancellation
Albert’s lines

7. Clinical tests of neglect – line bisection.
patient’s midline

8. Clinical tests of neglect – line bisection.
left
centre
right
Schenkenberg et al. 1980

9. Clinical Tests of Neglect – figure copying

10. Clinical Tests of Neglect – free drawing
Show video?

11. 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

12. Neglect and Imagery
Map of France test.

13. Spatial vs. Object based neglect.

14. 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?

15. Spatial vs. Object based neglect.
Axis-based neglect

16. Spatial vs. Object based neglect.
Figure – Ground Segregation

17. Spatial vs. Object based neglect.
Behrman and Tipper, 1994 – strongest evidence for object based neglect.

18. 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

19. Object based effects on extinction.
Gestalt Principles – visual occlusion

20. Temporal components of Neglect
Temporal Order Judgement (TOJ) task
Which came first?

21. Temporal components of Neglect
Phasic Alerting – arousal levels important in neglect too!

22. Temporal components of Neglect
Attentional Blink task – Hussain et al. Nature, 1997 C 3 M 7 H
TARGET 1
TARGET 2
t i m e
180
720
540
360
1800 …
stimulus onset asynchrony (SOA) T1 T2

23. Temporal components of Neglect
Attentional Blink task – Hussain et al. Nature, 1997
180
360
540
720
900
1260
1440
1620
1800
1080
single task
dual task
healthy controls
100 50
% correct
180
360
720
900
1260
1440
1620
1800
1080
100 50
% correct
540
single task
dual task
neglect patients

24. Break 1

25. What happens to neglected information?
The Burning House example.
Which house would you prefer to live in?
The top one.
Why?
Roomier, especially in the attic.

26. Implicit Processing in Neglect – illusions.
Line bisection in the Judd and Muller-Lyer illusions

27. 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

28. 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

29. Object specific extinction
Target specific – two forks lead to greater extinction than a fork and a key (Rafal, 1996).

30. Unconscious activation in extinction
right striate and extrastriate regions activated for extinguished stimuli
Rees et al Brain

31. What happens to neglected information?
The Burning House.
What would happen if a different question was asked?
Which house is warmer?

32. Implicit processing in neglect using
the Flanker Task
Colour flanker E O
Letter flanker
Unidimensional Stimuli. RT c n i

33. Colour and form processing in blindsight
using the flanker task.
flankers in sighted field
flankers in blind field O E E O
congruent
incongruent
congruent
incongruent

34. Blindsight patient AG – occipital lesion.R
Colour flankers
Letter flankers
800
850
900
950
1000
1050
1100
sighted
blind C I RT
800
850
900
950
1000
1050
1100 C I
sighted
blind RT

35. Implicit Processing in Neglect – flanker task.
Neglected flankers are nevertheless processed (Danckert et al. 1999) JS
star cancellation
(LVF/RVF)
letter cancellation
(LVF/RVF)
simple
detection
(LVF/RVF)
line
bisection
4 / 25
0 / 14
+ 43.3
0 / 100

36. Patient JS - Unidimensional flanker performance.
neglected flankers
perceived flankers
800
750
53 msec
cong
incong
73 msec
cong
incong
mean VRT (msec)
700
650

37. E E E O E E E O E O E O The Flanker Task: Bidimensional Stimuli.
identify colour
identify letter E E
double congruence
(CD) E O E
single congruence
(CS) E E O
single incongruence
(IS) E O
double incongruence
(ID) E O

38. data driven E E O E E O
goal driven

39. Goal-driven selection is dominant.
480
n.s.
COLOUR
470
LETTER
460
REACTION TIME (msecs)
n.s.
450
440
430
420
IDENTIFY
LETTER E E O O E E E E
IDENTIFY
COLOUR E O E E E E O E CD CS IS ID

40. Patient JS - Bidimensional flanker performance.
perceived flankers
neglected flankers
600
620
640
660
680
700
720
740
760
780
800
median VRT (msec) CD CS IS ID
name letter
name colour E E O E E O E E E O E O

41. 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!

42. Motor control in Neglect
Line bisection in different regions of space
Pointing to targets
TOJ pointing
Motor imagery

43. Clinical hints
cancellation tasks

44. Line bisection in near and far space
Altitudinal neglect
neglect of near space
neglect of lower visual field

45. 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

46. Pointing to targets Pointing and bisecting LEDS
Goodale et al. Can J Psych, 1990

47. Pointing to targets Pointing and bisecting LEDS bisection errors
Goodale et al. Can J Psych, 1990

48. Pointing to targets
Goodale et al. Can J Psych, 1990

49. Temporal order pointing in patient PB (neglect).
Point to which target appeared first.
-50 50
100
150
200
250
x - position (mm)
y - position (mm)
Patient PB - left target
(incorrect first response)

50. Speed accuracy trade offs.
left to right
near to far

51. Velocity profiles in Patient LR (neglect).
Higher peak velocity for rightward movements of either hand
Longer deceleration periods for leftward and near movements of either hand. R L R L R L R L R L
200
velocity (cm/sec)
100
velocity (cm/sec) 2 4 6 8 10 12
time (sec)

52. Motor Imagery

53. Movement duration for the VGPT
2.5
Movement duration for the VGPT
2.7
2.9
3.1
3.3
3.5
3.7
3.9 30
14.9
7.5
1.9
target width (mm)
movement duration (sec)
imagined
movements
actual
movements

54. Patient LR – Contralesional hand (L)
target width (mm) 4 6 8 10 12 14 16 18 30
14.9
7.5
3.7
1.9
Patient LR – Contralesional hand (L)
movement duration (sec) 5 7 9 11 13
real movements
imagined movements

55. Patient LR – Ipsilesional hand (R)
movement duration (sec)
target width (mm) 6 7 8 9 10 11 12 13 14 15 30
14.9
7.5
3.7
1.9 4
4.5 5
5.5
6.5
8.5
real movements
imagined movements

56. 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
t i m e
perform movements while imagining
the previously viewed target

57. Control subject MR real movements imagined movements imagined targets2
2.5 3
3.5 4
4.5 5 30
14.9
7.5
3.7
1.9
target width (mm)
movement duration (sec)
Control subject MR
real movements
imagined movements 30
14.9
7.5
3.7
1.9
target width (mm) 2
2.5 3
3.5 4
4.5 5
movement duration (sec)
imagined movements
imagined targets

58. Imagining the target vs. imagining the whole movement.
Patient LR
Imagining the target vs. imagining the whole movement.
target width (mm)
5.5
6.1
6.5
6.9
7.1 30
14.9
7.5
3.7
1.9
duration (secs)
imagined movements
imagined targets

59. Pointing without vision of the hand.3
3.5 4
4.5 5
5.5 6
6.5 30
14.9
7.5
3.7
1.9
target width (mm)
duration (sec)
real movements (with vision of hand)
imagined movements
real movements
(without vision of hand)

60. 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)

61. Spatial re-mapping – retinal co-ordinates

62. Spatial re-mapping – updated representation.

63. Saccadic Dysmetria
Patient with a fronto-parietal lesion can’t do the double-step saccade task when first saccade is contralesional

64. Saccadic Dysmetria
No problem with visually guided saccades (targets presented for 500 msec)
contra move first
contra move second

65. 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

66. Break 2

67. Rehabilitation of Neglect
Caloric stimulation
Neck muscle vibration
Restriction of the ipsilateral limb
Prism Adaptation

68. 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

69. 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

70. Prism adaptation – is neglect really ameliorated?
patient LR showed classic neglect bias on chimaeric faces test
eye movement pattern also showed neglect

71. Patient LR – chimaeric faces.
Which one is happier? Top or bottom?
Controls – bias towards left smiling face
Neglect – bias towards right smiling face

72. Perceptual task. Eye movement 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

73. Prism adaptation for LR.
Subjective judgment of straight ahead.

74. Eye movements to chimaeric faces - controls.

75. LR’s eye movements pre and post.

76. Eye movements pre and post.
Ferber, Danckert, Joanisse, Goltz & Goodale 2002 Neurology (in press)

77. 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!

78. 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

79. 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!

80. 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!

81. Motor Intention patients may be aware of stimuli but may fail to act
reduced capacity vs. ipsilesional bias
exploration deficits – searching by touch or eyes
Bisiach’s pulley system A E
congruent movement
incongruent movement

82. 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?

83. 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!)

84. 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”

85. 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.?

86. Acknowledgements Flanker tasks in neglect and blindsight Paul Maruff
Glynda Kinsella
Steven de Graaff
Jon Currie
Murat Yucel
Carly Ymer
Motor imagery in neglect
Susanne Ferber
Mel Goodale
Timothy Doherty
Prisms in neglect
Susanne Ferber
Herb Goltz
Marc Joanisse
Mel Goodale
Yves Rossetti
Motor control in neglect
Susanne Ferber
Mel Goodale
Haitao Yang

87. End of Lecture