Unilateral Neglect Flashcards
What is unilateral neglect
- occurs as a result of right hemisphere brain damage
- causes impairment to functioning of left side space
Brain (1941) unilateral neglect patient
- when the patient was asked to describe route home they were only able to describe right turnings and not left.
- if they were to walk home they would also only make right turnings
Paterson and Zangwill (1944)
Wounded from war
- Patient collides with objects on their left side and missed food on left side of plate
- patient neglected upper left extremity of their own body even though they had good motor power.
Extinction example
- mild form of neglect
- when watching doctor moving left and right hand separately, they can see this
- When watching left and right hand moving at the same time, they are only able to see right hand moving
- This is mild neglect as it only occurs when their is competition for attention
Clinical tests for neglect
- Drawing, only draw right side
- Line bisection, judgment off
- Cancellation tasks, only do right side
- Reading, errors on left side of word, lock instead of clock
Main causes of neglect
- Stroke is most common cause
- blood supply cut to part of brain
Nature of brain damage associated with neglect
- damage to right hemisphere as it is dominant I spatial cognition in humans
- lesions in posterior parietal cortex, frontal lobe and subcortical regions
- common to have left sided paralysis
What is Anosognosia
- Patients don’t accept having paralysis
- When patients are asked to move their arm they will say they are choosing not to
- Or the just aren’t bothered about paralysis
- occurs in 20-30% of paralysis
Can neglect be as a result of Hemianopia?
NO
- it occurs during mental images i.e. drawing clock from memory which means it isn’t as a result of not being able to physically see left side
- Hemianopic patients don’t show neglect
- Also if it was as a result of visual field, patients could just move eyes to see more
‘Piazza del duomo’ demonstration
Bisiach and Luzzatti
- two patients In hospital asked to describe familiar scene i.e the cathedral in Milan
- when drawing views of cathedral, left side was neglected
- they neglected the left side depending on which way they were facing
Residual processing of extinguished information
Volpe et al (1979)
- five patients with left extinction
- asked if same or different images on each side of the page, they could do this
- when asked what images are they could only say right side which was a comb
Burning house study
Marshall and Halligan (1988)
- Single case study on patient P.S.
- when describing what the houses looked like they said the same even though one was burning and the other wasn’t
- when asked which they wanted to live in they stated non burning house
Dissociations and double dissociations
- Reading and face recognition involve separate cognitive processes as patient x had impaired reading but not face recognition
- although they could have been impaired as reading is harder than face recognition
- patient y can read but not recognise faces, confirms there’s two separate systems
Spatial Neglect
(Dissociations in Neglect)
- scan paths show failure to scan left side of scene (Karnath, 1994)
Object based neglect
(Dissociations in Neglect)
Gainotti, 1972, some patients only neglect left side of the actual object not objects on the left side of the page
Young et al (1992) neglect of left side of images which have been blended into one, but when images were separated into 2, they could identify. I.e. rugby ball and camera meted, they would say rugby ball as the ball was the right side of the image until split then they could identify
Neglect Dyslexia
(dissociations in neglect)
Young et al (1991)
- neglect dyslexia occurred for words positioned anywhere on the page (missing first letters)
- whole world neglect only occurred when words located on left side of page
Neglect of near versus far spaces
(dissociations in neglect)
- line bisection task with darts, when near there was severe left neglect
- when far, no neglect meaning accurate bisection
- this same task was repeated with a torch and same results found
Motor neglect
(dissociations in neglect)
- patients had to reach towards green lights
- when reaching towards green lights on left hand side, it was initially very slow reaction (when they started in the middle)
- when participants stared towards the left, their responses were much faster
Mattingley et al (1988)
Representational model of neglect
(Bisiach and Luzzatti, 1978)
- Neglect is failure to construct a representation of the left side of space.
- Also reflects failure to construct neural representation
Attentional model of neglect
- failure to orient covert attention
Posner et al, 1984 - response time normal for left targets after left cue, response times for left targets very long after right cue.
- showed increases in reaction time in responding covertly to s stimulus on the left following right cue.
Kinsbourne’s Attentional model
- each hemisphere controls attentional orienting in contraversive direction i.e. left hemisphere = rightward orienting and visa versa
- the left hemisphere has a stronger orienting bias but in a intact brain these would balanced
- right brain damage leaves intact left hemisphere overactive
- neglect patients have deficit orienting attention to left and also show rightward bias.
Heilman’s Attention model
- left hemisphere can only direct attention to right side space
- neglect reflects a failure to attend and intent.
Premotor model of neglect
- neglect is as a result of spatial awareness
- brain damage produces secondary consequences of damage to the spatial representations
Three separate regions of space
- personal, own body space
- peripersonal, area around upper body within reaching distance
- extrapersonal, beyond reaching distance
