Unilateral Neglect Flashcards
What is unilateral neglect?
Following right hemisphere brain damage, a patient without impairment of intellectual functioning appears to ignore, forget, or turn away from the left side of space
Patients fail to report, respond or orient to meaningful stimuli presented on the affected side
(W., R Brain, 1941)
Reported three patients with unilateral parietal lobe lesions in whom the primary problem was varying degrees of perceptual difficulty.
“When asked to describe how she would find her way from the tube station to her flat, she described this in detail correctly and apparently visualising the landmarks, but she consistently said right instead of left for the turnings except on one occasion”.
Everyday examples of Neglect
Patients may:
- eat food on the right side of plate
- dress only right side of own body
- shave the right side of face
Clinical tests of Neglect:
- Drawing
-copy of flower
-clock drawing from memory - Line bisection
A quick measure to detect the presence of unilateral spatial neglect (USN). To complete the test, one must place a mark with a pencil through the centre of a series of horizontal lines
3.Cancellation tasks
Largely used to evaluate visuospatial function and attention.
Causes of Neglect
Unilateral neglect is most caused by a stroke
- Affects 150,000 people in UK
-Blood supply to part of brain is cut off – resulting in damaged tissue
Nature of brain damage associated with Neglect:
-Neglect is most observed in humans following damage (stroke) to the right hemisphere (left neglect)
-Left parietal damage rarely produces right-sided neglect and quicky recovers
-Patients often have left-sided paralysis (hemiplegia)
Anosognosia
-An inability to recognise a defect or disorder that is clinically evident
-A system of severe mental illness experienced by some that impairs a person’s ability to understand and perceive his or her illness
-A well-known example of anosognosia is often found in hemi-spatial neglect patients
Spatial Neglect (Karnath, 1994)
-Refers to neglect reflected in eye movement behaviour
-Scenes chosen to guide top-down active search of left side
Eye movement scan paths
-Failure to scan left side of a scene (spatial neglect)
Spatial neglect is a neuropsychological condition that occurs mainly due to damage to the right cerebral hemisphere after the right middle cerebral artery stroke
Object-based Neglect (Gainotti, 1972)
Some patients neglect left side of objects but not the left side of space (scene)
(Marshall & Halligan, 1993)
- Right MCA stroke
- Male 54 years old
- Copied whole plant – neglected stem on left side
Neglect Dyslexia
Neglect dyslexia is a neuropsychological syndrome in which patients commit consistently lateralised letter omission, addition, and substitution errors when reading individual words
Examples of neglect dyslexia:
Neglect dyslexia can occur in multiple spatial scales when a reader is confronted with text:
- omission of the entire left page of an open book
- omission of a left text column
- omission of the left side of sentences in a newspaper
- omission of the left word in a phrase
- omission of the left letters in a word
Motor Neglect (Laplane and Degos, 1983)
Refers to the underutilisation of the affected limb compared to the healthy one following brain damage despite normal muscle strength, reflexes, and sensations
Representational model of neglect (Bisiach & Luzzatti, 1978)
Provided evidence in the representational model of neglect, that unilateral spatial neglect is not only a disorder of visual perception, but can also affect mental representations such that patients fail to report the left side of scenes or objects in mental imagery.
- Neglect reflects a failure to construct a neural representation of the external environment
- Damage to one hemisphere assumed to impair the representation of the opposite side of space
- Neglect could reflect a failure to construct a representation of the left side of space
Piazza del Duomo (Bisiach & Luzzatti, 1978)
Two patients in hospital asked to describe a familiar scene (Cathedral square in Milan) from memory
Findings
- Reported landmarks on the right not those on the left both imaginary viewing positions
- Failure to construct a representation of left space
Attentional model of neglect (Posner et al., 1984)
-Neglect reflects a failure to orient covert attention
-Shifts of attention require (disengagement – move – re-engagement)
Findings
- Parietal patients showed increases in reaction time in responding covertly to a stimulus on the left, following a cue to the right
- Deficit in disengaging attention when leftward shift is required
Premotor model of neglect (Rizzolatti & Berti, 1990, 1993)
Premotor model of neglect refers to the intentional motor bias from the ipsilesional side to an object in the contralesionally side of space
-Can be viewed as a combination of attentional and representational accounts
-Attention involved in selection of an object for action
-Spatial attention involves multiple circuits which sub-serve different regions of space
Neglect is primarily a disorder of spatial awareness
-Spatial awareness arises from joint activity of several cortical and subcortical areas
-Combined neural activity in this neural circuit form representations for the control of goal-direction action
-Damage produces loss of awareness, and the attentional deficits are secondary consequence of damage to the spatial representations
