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

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Presentation on theme: "Fundamentals of Neuroscience Unilateral Neglect (Lec 01) James Danckert PAS 4040 Web page for slides"— Presentation transcript:

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) Regardless of who is right – the lesion is in tertiary association cortex – integration of multiple sensory signals and extensive connections with frontal areas. Karnath, et al. – superior temporal gyrus (based on MRI)

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. Albert’s lines Star cancellation

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

8 Clinical tests of neglect – line bisection. Schenkenberg et al leftcentreright

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 rightDSS 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 … stimulus onset asynchrony (SOA) T1 T2

23 Temporal components of Neglect Attentional Blink task – Hussain et al. Nature, single task dual task healthy controls % correct % 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? A.The top one. Why? A.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 rightDSS 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 RT cni Unidimensional Stimuli.

33 Colour and form processing in blindsight using the flanker task. flankers in sighted field flankers in blind field OOEO EOOO congruentincongruentcongruentincongruent

34 Colour flankers Letter flankers sightedblind CICI RT CICI sightedblind RT Blindsight patient AG – occipital lesion. LR

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) linebisection simpledetection(LVF/RVF) 4 / 25 0 / / 100

36 Patient JS - Unidimensional flanker performance mean VRT (msec) 53 msec congincong 73 msec congincong neglected flankers perceived flankers

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

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

39 Goal-driven selection is dominant REACTION TIME (msecs) E E IDENTIFY LETTER IDENTIFY COLOUR LETTER COLOUR E E E E E O E O E E E O E O CDCSISID n.s.

40 median VRT (msec) CDCSISIDCDCSISID Patient JS - Bidimensional flanker performance. name colour name letter perceived flankersneglected flankers E E E O E E E O E E E O E E E O

41 What happens to neglected information? Bottom-up – information is still processed in extrastriate visual cortex All of this is despite a lack of awareness! Top-down – goals can influence how the information is processed

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 lower visual field neglect of near space

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 Goodale et al. Can J Psych, 1990 bisection errors

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 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. RLRLRLRLRL time (sec) velocity (cm/sec) velocity (cm/sec)

52 Motor Imagery

53 2.5 Movement duration for the VGPT target width (mm) movement duration (sec) actual movements imagined movements

54 target width (mm) Patient LR – Contralesional hand (L) movement duration (sec) target width (mm) real movements imagined movements

55 real movements imagined movements Patient LR – Ipsilesional hand (R) movement duration (sec) target width (mm) target width (mm)

56 view target for 2 sec perform movements while imagining the previously viewed target 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? t i m e

57 real movements imagined movements target width (mm) movement duration (sec) imagined movements imagined targets target width (mm) movement duration (sec) Control subject MR

58 Patient LR Imagining the target vs. imagining the whole movement. target width (mm) duration (secs) imagined movements imagined targets

59 Pointing without vision of the hand target width (mm) duration (sec) real movements (with vision of hand) real movements (without vision of hand) imagined movements

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 firstcontra 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 firstcontra 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. 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. PREPOST

76 Eye movements pre and post. PREPOST 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 AE 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 motor neglect (fronto-parietal lesions) pure neglect (inferior parietal or STG for the true connoisseur!) extinction (superior parietal – but what about simultanagnosia and optic ataxia?)

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


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