Presentation on theme: "Fundamentals of Neuroscience Unilateral Neglect (Lec 01)"— Presentation transcript:
1Fundamentals of Neuroscience Unilateral Neglect (Lec 01) James Danckert PAS 4040Web page for slides
2Unilateral Neglectfailure to respond to or attend to contralesional stimuliusually a result of right parietal lesionscurrent controversy whether the inferior parietal lobe or the superior temporal gyrus is the critical lesion site for neglect
3Critical 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.
5Unilateral Neglectmost commonly observed for the visual modality (so often called visual neglect)can have multimodal neglect – auditory and tactile neglect most commoncan occur following left parietal lesions – usually less severe and recovers more frequently
6Clinical tests of neglect – cancellation tasks. Star cancellationAlbert’s lines
7Clinical tests of neglect – line bisection. patient’s midline
8Clinical tests of neglect – line bisection. leftcentrerightSchenkenberg et al. 1980
14Chimaeric FacesHealthy controls prefer faces smiling on left (Q reading bias?)Neglect patients prefer faces smiling on right – even though they “see” the whole faceWhich one is happier?
15Spatial vs. Object based neglect. Axis-based neglect
16Spatial vs. Object based neglect. Figure – Ground Segregation
17Spatial vs. Object based neglect. Behrman and Tipper, 1994 – strongest evidence for object based neglect.
18Neglect 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 leftsingle rightDSS trial
19Object based effects on extinction. Gestalt Principles – visual occlusion
20Temporal components of Neglect Temporal Order Judgement (TOJ) taskWhich came first?
21Temporal components of Neglect Phasic Alerting – arousal levels important in neglect too!
22Temporal components of Neglect Attentional Blink task – Hussain et al. Nature, 1997C3M7HTARGET 1TARGET 2t i m e1807205403601800…stimulus onset asynchrony (SOA)T1T2
25What 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.
26Implicit Processing in Neglect – illusions. Line bisection in the Judd and Muller-Lyer illusions
27Illusions and extinction improvement of extinction for illusory figuresillusory squareno illusory squarewhen asked “how many objects did you see?” less extinction was observed for illusory figures
28Neglect 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 leftsingle rightDSS trial
29Object specific extinction Target specific – two forks lead to greater extinction than a fork and a key (Rafal, 1996).
30Unconscious activation in extinction right striate and extrastriate regions activated for extinguished stimuliRees et al Brain
31What happens to neglected information? The Burning House.What would happen if a different question was asked?Which house is warmer?
32Implicit processing in neglect using the Flanker TaskColour flankerEOLetter flankerUnidimensional Stimuli.RTcni
33Colour and form processing in blindsight using the flanker task.flankers in sighted fieldflankers in blind fieldOEEOcongruentincongruentcongruentincongruent
34Blindsight patient AG – occipital lesion. RColour flankersLetter flankers800850900950100010501100sightedblindCIRT800850900950100010501100CIsightedblindRT
35Implicit Processing in Neglect – flanker task. Neglected flankers are nevertheless processed (Danckert et al. 1999)JSstar cancellation(LVF/RVF)letter cancellation(LVF/RVF)simpledetection(LVF/RVF)linebisection4 / 250 / 14+ 43.30 / 100
41What happens to neglected information? Top-down – goals can influence how the information is processedBottom-up – information is still processed in extrastriate visual cortexAll of this is despite a lack of awareness!
42Motor control in Neglect Line bisection in different regions of spacePointing to targetsTOJ pointingMotor imagery
44Line bisection in near and far space Altitudinal neglectneglect of near spaceneglect of lower visual field
45Line bisection in near and far space PET in normals – line bisection in near and far spaceIntraparietalVentral frontalNEAR SPACEVentral occipitalFAR SPACEWeis et al. Brain, 2000
46Pointing to targets Pointing and bisecting LEDS Goodale et al. Can J Psych, 1990
47Pointing to targets Pointing and bisecting LEDS bisection errors Goodale et al. Can J Psych, 1990
48Pointing to targetsGoodale et al. Can J Psych, 1990
49Temporal order pointing in patient PB (neglect). Point to which target appeared first.-5050100150200250x - position (mm)y - position (mm)Patient PB - left target(incorrect first response)
50Speed accuracy trade offs. left to rightnear to far
51Velocity profiles in Patient LR (neglect). Higher peak velocity for rightward movements of either handLonger deceleration periods for leftward and near movements of either hand.RLRLRLRLRL200velocity (cm/sec)100velocity (cm/sec)24681012time (sec)
53Movement duration for the VGPT 2.5Movement duration for the VGPT18.104.22.168.22.214.171.124014.97.51.9target width (mm)movement duration (sec)imaginedmovementsactualmovements
54Patient LR – Contralesional hand (L) target width (mm)46810121416183014.97.53.71.9Patient LR – Contralesional hand (L)movement duration (sec)5791113real movementsimagined movements
55Patient LR – Ipsilesional hand (R) movement duration (sec)target width (mm)67891011121314153014.97.53.71.944.5126.96.36.199real movementsimagined movements
56Was the poor relationship between real and imagined movements for LR due to a loss of visual and/orproprioceptive feedback of the moving hand?view target for 2 sect i m eperform movements while imaginingthe previously viewed target
58Imagining the target vs. imagining the whole movement. Patient LRImagining the target vs. imagining the whole movement.target width (mm)188.8.131.52.97.13014.97.53.71.9duration (secs)imagined movementsimagined targets
59Pointing without vision of the hand. 33.544.555.566.53014.97.53.71.9target width (mm)duration (sec)real movements (with vision of hand)imagined movementsreal movements(without vision of hand)
60Motor control in Neglect Path curvature is controversial – difficulty replicatingRole in spatial components of movements relatively uncontroversialProbably controls the spatial component of movements of both limbsTMS and fMRI data suggesting right FEF important for saccades to both contralateral and ipsilateral spacePET 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)
67Rehabilitation of Neglect Caloric stimulationNeck muscle vibrationRestriction of the ipsilateral limbPrism Adaptation
68Prism 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 directionafter effects lead to better processing of previously neglected stimuli
69Prism Adaptation – Rossetti and colleagues effects of prism adaptation not restricted to adapted hand or eyevisual imagery, postural balance also affectedafter 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
70Prism adaptation – is neglect really ameliorated? patient LR showed classic neglect bias on chimaeric faces testeye movement pattern also showed neglect
71Patient LR – chimaeric faces. Which one is happier? Top or bottom?Controls – bias towards left smiling faceNeglect – bias towards right smiling face
72Perceptual task. Eye movement task. 6 different pairs of faces top and bottom smiling faces and left and right sided smilingfaces randomised across trials3 different durations of stimulus – 500, 1000 and 1500 msecEye movement task.18 different faces presented individuallysimply explore the full extent of the faces6 of the 18 faces were chimaeric ‘probes’durations of stimuli –10 sec
73Prism adaptation for LR. Subjective judgment of straight ahead.
76Eye movements pre and post. Ferber, Danckert, Joanisse, Goltz & Goodale 2002 Neurology (in press)
77Perception 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’sawareness of the chimaeric faces!
78Prism adaptation – is neglect really ameliorated? after prism adaptation LR’s eye movements now fully explored the facesdespite a dramatic change in the pattern of eye movements he still chose the right sided happy faces on 92% or trialsmore 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
79Mechanisms of NeglectWhy is neglect more common after right parietal lesions?Kinsbourne – attentional asymmetry (global vs. local)Ferber – spatial working memoryGoldberg – novelty seeking?Danckert – some combination of all three?Object-based neglect is still puzzling!
80Attentional Hypotheses inattentionunaware of left stimuli (cuing can correct this)ipsilesional biaseach hemisphere orients contralaterally and inhibits orienting of the opposite hemispherehyper vs. hypo orienting – why is neglect more common from right parietal lesions?ipsilesional bias vs. reduced contralesional capacity?disengage deficitipsilesional cues led to longer RTs to contralesional targets (contra cues with ipsi targets were not affected as much)reduced sequential attentional capacityneglect of centre!
81Motor Intention patients may be aware of stimuli but may fail to act reduced capacity vs. ipsilesional biasexploration deficits – searching by touch or eyesBisiach’s pulley systemAEcongruent movementincongruent movement
82Other factors to consider Spatial working memoryour neglect patient showed a SWM deficit for vertically arranged stimuliif it doesn’t get into SWM (or processes of SWM are deficient – more limited than usual) then it won’t make it into awarenessNovelty vs. familiarityif 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?
83Introducing the Neglect Syndromes extinction(superior parietal –but what about simultanagnosiaand optic ataxia?)motor neglect(fronto-parietal lesions)pure neglect(inferior parietal orSTG for the true connoisseur!)
84Neglect and anosagnosia anosagnosia – denial or unawareness of impairment (even extends to inanimate objects!)caloric stimulation ameliorates anosagnosia temporarilydifference between insight and anosagnosiaknowing “what” (or “that something is so”) vs. knowing “how” or “why”
85Neglect 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.?
86Acknowledgements Flanker tasks in neglect and blindsight Paul Maruff Glynda KinsellaSteven de GraaffJon CurrieMurat YucelCarly YmerMotor imagery in neglectSusanne FerberMel GoodaleTimothy DohertyPrisms in neglectSusanne FerberHerb GoltzMarc JoanisseMel GoodaleYves RossettiMotor control in neglectSusanne FerberMel GoodaleHaitao Yang