Attentional Neglect Flashcards
What is Neglect syndrome?
Unilateral spatial neglect involves loss of perceptual awareness for stimuli on the contralesional side of space.
It is a heterogeneous syndrome characterised by deficits of attention and spatial working memory; neglect can affect just one sensory modality, or several.
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A disorder of attention that occurs after damage to one side of the brain (usually right-sided, parietal lobe often implicated e.g., MCA stroke). Clinically presenting as a failure to attend to one side of space (often the left, if r-hemi dmg).
May present as:
- acting as though affected side of space has ceased to exist (contralateral to lesion)
- can also be a bias towards the ipsilesional side (e.g., in orientating)
- ignore food on one side of their plate
fail to shave or make-up one side of their face
- bump into objects on one side
- fail to read text from one side of the page
NOT A VISUAL/SENSORY deficit!. have to dissociate it from sensory, you can compensate for sensory, but typically people don’t compensate for neglect.
What is spatial extinction?
Can detect stimulus on either side of space, but lose the ability to attend to one side of space (bad side) when there is a competing stimuli on the other (good side) (simultaneous processing)
This is a frequent component of neglect, but can also occur in the absence of ‘florid’ neglect.
Can be visual, but also sound and touch!
What attentional deficits are seen in neglect?
- SPATIAL
a) Spatial attention (e.g., bells test, line bisection) ignore contralateral side of space
b) Conjunction visual search - the relationship between number of distractors and reaction time is STRONGER for patients with neglect - i.e., their reaction time suffers more the more distractors there are! (the MORE ATTENTION IS LOADED ON).
2. TEMPORAL (non-spatial)
a) attentional blink is enhanced in neglect - patients able to just detect ‘x’, but when you ask them to detect the ‘white n’ and then the ‘x’ (loading up attention) they have a greater attentional blink than controls.
3. Object-based neglect - connected objects originally in ‘bad side’ that are then rotated into the ‘good side’ and are still not perceived! - this does not occur unless the objects are connected (e.g., by a line).
4. MULTI-MODAL attentional deficits (e.g., tactile neglect, auditory neglect - even in imagined visual representations! [internal mental world]).
[Hint - think about the various forms of selective attention!]
What are three ways to measure whether patients with neglect are still processing information on their ‘bad side’ but are not aware of it (i.e., processing without awareness)
indirect measures of neglect (i.e., to what extent do patients process information of their neglected side?)
- Biase task - e.g., similar houses, one is on fire on the neglect side - even though patient says they are ‘the same’ they were more likely say they would rather live in the one without fire). –> suggests some processing of the stimulus even in the absence of awareness.
- Semantic priming - patient asked to say whether a target (in their good field) is a animal or fruit. and a ‘prime’ is also presented in their bad field. The ‘prime’ can be the same picture (e.g., a duck for the target duck), a picture in the same category (another animal), or opposite category (incongruent) - the patient if asked would not be able to ‘see’ these ‘primes’. YET, the neglected primes lead to faster reaction to the target if there is congruence, rather than incongruence between the prime and the target.
- SUGGESTS some processing of the stimulus even in the absence of awareness. - Lexical decision: semantic relatedness - faster lexical decision (word versus non-word) when prime (in neglected space) and target (in good space) were related than when they were unrelated…..
All suggest unconscious processing of neglected space.
What kinds of neglect should you test for clinically?
- Visual, auditory, tactile and object-based neglect!
- Egocentric deficits (relative to self) are most common. But can get stimulus-centered neglect (midline of stimulus regardless of position of space and object-centred deficits (midline of object regardless of both orientation and position in space).
How can you distinguish between neglect and visual field sensory loss? (loss of vision; hemianopia)
- Patients with sensory loss tend to actively compensate (e.g., move head) for visual field defects as they are aware of the deficits.
- Patients with neglect do not tend to compensate for their neglect, typically anasognosic (lack insight) - neglect has an attentional aetiology rather than sensory.
you can have large lesions that result in BOTH sensory and attentional deficits).
What kind of lesions are most likely to result in neglect?
- the critical lesion site that causes neglect involves the inferior parietal lobe (RH>LH), although a network of areas including the IPL and TPJ, temporal gyrus and ventromedial prefrontal cortex has also been implicated
- – Most common after middle cerebral artery stroke - usually larger lesions.
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LOTS OF DEBATE!!
– Most studies show Right temporal parietal junction - but lots of variability.
– it has also been suggested that there is a network of critical areas: temporo-parietal junction (TPJ) and inferior parietal lobule (IPL) superior/middle temporal gyrus. Ventromedial prefrontal cortex -and that the features of an individuals neglect might reflect what part of the network is damaged.
– CONTRADICTORY FINDINGS (some studies suggest primarily ventral attentional network affected in spatial neglect OTHERS suggest parietal-frontal regions most often affected (dorsal network!!)) – may underlyieheterogeneity.
(studies of MCA and neglect might be misleading b/c most studies don’t have control groups with MCA stroke but not neglect!)
Describe the natural recovery timeframe for spatial neglect.
Neglect either resolves spontaneously or can remain a significant problem for many years.
- Neglect often present immediately (within 3 days) following right (55%) AND left (42%) hemisphere stroke and typically recovers on it’s own, usually very quickly.
- for a portion of patients right hemisphere strokes who showed early neglect (33%), the neglect symptoms persist beyond 3 months.
What is a ‘top-down’ approach to the treatment of neglect?
Examples?
- voluntary compensatory strategies
e. g.,
- cues to attend to the bad side
- scanning retraining
Problem is! they require some awareness of deficit (or LOTS of prompting!!)
What is a ‘bottom-up’ approaches to the treatment of neglect?
(examples?)
- Aim to modify underlying impairment (do not require awareness of deficit)
e. g.,
- Prismatic adaptation
- Vestibular stimulation (cold water in ear)
- Optokinetic stimulation
What are some ‘mixed’ (bottom-up and top-down) or other approaches to treatment of neglect?
- Ipsilateral eye-patching
- pharmacological treatments
- Transcranial magnetic stimulation (disrupt over-activity in the intact [left] hemisphere)
Divide the following treatments for neglect into ‘bottom-up’ ‘top-down’ and ‘mixed’/other.
- pharmacological treatments
- Prismatic adaptation
- Transcranial magnetic stimulation- cues to attend to the bad side
- scanning retraining
- Vestibular stimulation (cold water in ear)
- Ipsilateral eye-patching
- Optokinetic stimulation
Top-down (i.e., voluntary compensatory strategies)
- cues to attend to the bad side
- scanning retraining
Bottom-up (i.e., modify underlying impairment)
- Prismatic adaptation
- Vestibular stimulation (cold water in ear)
- Optokinetic stimulation
Mixed/other
- Ipsilateral eye-patching
- pharmacological treatments
- Transcranial magnetic stimulation
cochrane review (Bowen et al., 2013) “the effectiveness of cognitive rehabilitation interventions for reducing the disabling effects of neglect and increasing independence remains unproven”
NEGLECT SUMMARY (read only)
- Unilateral spatial neglect involves loss of perceptual awareness for stimuli on the contralesional side of space
- the critical lesion site that causes neglect involves the inferior parietal lobe (RH>LH), although a network of areas including the IPL and TPJ, temporal gyrus and ventromedial prefrontal cortex has also been implicated
- neglect is a heterogeneous syndrome characterised by deficits of attention and spatial working memory; neglect can affect just one sensory modality, or several
- There can be considerable implicit or “unconscious” perception of neglected or extinguished stimuli
- Neglect either resolves spontaneously or can remain a significant problem for many years
What are some promising treatment avenues for neglect?
- Intervention involving visuo-motor adaption to optical prisms and other sensory stimulation can induce some improvement (TMS is a promising avenue.
Do people with neglect still process stimuli they are unaware of in the neglect side of space?
Yes - studies of biases and semantic priming suggest there can be considerable implicit or “unconscious” perception of neglected or extinguished stimuli (even when unaware of that stimuli).
