W11 - Attention Flashcards
What the task examining voluntary attention? What are other names of voluntary attention
Posner Cueing Task
- Meaures Endogenous/Covert attention
- covert = not moving eyes
What is endogenous attention and why does posner cueing task examine this
Orientation of attention to the cue is
- Driven by goals (internally)
- Not due to environment/physical features
What is unilateral spatial neglect
- Symptom of patients behaving as though parts of objects, and or the world around them do not exist
- They are largely unaware of this deficit
- Show extinction (unlike heminaopia)
What brain damage is associated with unilateral spatial neglect
- Stroke
- Brain injury to right parietal and frontal cortex
Do patients with stroke always have unilateral spatial neglect. Why?
- People with stroke largely loses this neglect.
- Stroke = Pressure
- So after stroke dissipates, pressure goes back to normal, neglect dissipates
How do we examine unilateral spatial neglect.
At what spatial scales are these neglects
Line cancellation test
- Neglect may arise at different spatal scales within the same patient
- e.g. may ignore left page in book/left sided words
What is extinction?
Failure to perceive a stimuli contralateral to leision when presented simultaenously with stimuli ipsilateral to lesion.
How do we draw a distinction between spatial neglect and visual feild deficits?
Extinction
- Spatial Neglect:
- Will still repsond to unilateral presentation
- Visual Field Deficits
- Visual Field Damage
- Will not respond to unilateral presentation.
There are many studies showing different associations between neglect and brain regions. Why are there large variability?
- Different methods (e.g., CT, fMRI, DTI)
- How participants are selected, how long since stroke, what test used to measure neglect
-
Location of stroke (Naturalistic lesions)
- Some patients die after stroke, can’t locate…
What are the brain regions associated with neglect after confluence of imaging studies
- Posterior parietal lobe
- Temporoparietal junction (including STS)
PPL and TPJ (+STS)
What are the results of primate studies on neglect?
- Posterior pareital (by itself) does not cause neglect,
- Both posterior paretal cortex, TPJ (includes STS) together causes it
- Neglects are often temporary, not permanent
In a lot of structural work, what do studies often miss out
They often ignored where white matter damager occur, that might have disconnected frontal, temporal and parietal cortices
- Might be a disconnection syndrome
Other than TPJ, STS, and Posterior Parietal Lobe, wich other region has been found to cause neglect? What is the caveat
Damage to subcortical nuclei (caudate, putamen).
- Thought this might be due to disconnection: cortical hypoactivation to regions important for neglect like TPJ
Is neglect more common after left/right hemisphere damage
Right hemisphere damage is more common
(far less common in left-handed participants)
What are the models suggesting why neglect is more prominent after right-hemispheric damage?
- Representational Model
- Attentional Bias Model
Elaborate on the representation model of unilateral spatial neglect
- Right hemisphere represents right and left
- Left hemisphere tepresents right only
- Damage to left no neglect because right can maintain
Elaborate on the attentional bias model of unilateral spatial neglect
- Left and right have natural bias towards contralateral attention
- Bias is assymmetrical with left hemisphere being more strongly biased towards right hemispace
- that’s why we sit on the left
Saliency in Neglect Patients. What does it suggest
Saliency of objects in neglected / contralesional field is impaired
- Exogenous and endogenous (goal-driven) components of selective spatal attention are equally impaired
- Abnormally high salience of ipsilesional stiuli can prevent them from being filtered when task-irrelevant but they are a minority of examples
Saliency in dark room. Results and Implications?
Results
- Patients in dark room without stimuli show spatial lateralised bias (Bias to look to the right/ ipsilesional hemispace/’good side’)
- Eye movements reflect hemispatial bias. Gaze deviations are observed at rest
Implications
- Not a reduced salience of contralesional spatial deficits alone
- Also an imbalance in mechanism controlling in
- (a) controlling gaze; and
- (b) relevant to attention
Is spatial lateralised bias related to early/late visual process
Bias does not reflect early visual mechanism
There are 4 findings that supports inact early visual mechanism in neglect patients, which are
- Intact image segmentation of low-level visual features in the neglected visual field
- e.g. figure ground illusions in neglected side
- Normal contrast sensitivity
- Occipital cortex responds to visual stimuli in the contralesional hemispace, even under extinction presentation
- Contralesional visual stimuli prime faster response times for subsequent stimuli
- Unconscious processing