Spatial attention Flashcards
The Posner Cueing Task measures __ because __.
endogenous attention;
the orienting of attention to the cue is driven by the subject’s goals, rather than merely its physical features.
Unilateral spatial neglect is defined by __
the symptom of patients behaving as though parts of objects, and/or the world around them do not exist, and they are largely unaware of this deficit.
Unilateral spatial neglect is typically associated with strokes or brain injuries to __.
right parietal and frontal cortices (simultaneously).
In unilateral spatial neglect, patients will ignore the presence of \_\_ Might also fail to groom the \_\_. Not recognize their own \_\_. Their \_\_ may be oriented rightward.
persons or objects in the contralesional hemispace;
contralesional side of the body;
limbs on the contralesional side;
eyes, head and trunk
Unilateral spatial neglect may arise at different spatial scales within the same patient, e.g. ___
May ignore stimuli at the extreme left in their environment.
May also neglect the left page when reading a book, or the left hand words on a page, left sided letters in a word.
Patients with unilateral spatial neglect will prominently show extinction, which is __
Failure to perceive or act on stimuli contralateral to the lesion when presented simultaneously with stimuli ipsilateral to the lesion.
Extinction helps discriminate spatial neglect from visual field deficits (caused by damage in the visual pathway, e.g., optic nerve, or occipital lobe), because __
the patient wont respond to unilateral presentation if they
have the latter
Studies have highlighted that lesions of the __ are most likely to cause neglect.
Other studies have suggested the __.
Karnath and colleagues more recently have found in large samples associations with __.
right inferior parietal lobe centred on the angular gyrus;
right superior temporal cortex;
superior temporal gyrus, insula and basal ganglia
Neglect cortical mechanisms: The confluence of imaging studies has tended to implicate the
posterior parietal lobe and temporoparietal junction (including the superior temporal sulcus)
Monkey lesion studies have shown that lesions of the __ do not result in neglect, whereas ‘neglect-like’ symptoms can be produced when the __ are lesioned.
Primate lesion studies have demonstrated that most discrete lesions don’t result in permanent neglect, in fact, they __.
posterior parietal cortex;
superior temporal and temporoparietal junction regions;
typically resolve quite quickly
Neglect patients, especially in severe cases, have white matter damage, that might have disconnected __.
White matter damage that is more permanent most often involves a dorsal region lateral to the ventricle, particularly the __.
frontal, temporal and parietal cortices;
arcuate and superior longitudinal fasciculi, which run parallel to the ventricle
Neglect cortical mechanisms: Lunven and Bartolomeo (2017) review makes the argument for the __, rather than a focal cortical syndrome.
Intrahemipsheric disconnection, in particular within the right hemisphere’s __.
disconnection syndrome of interconnected cerebral areas;
fronto-parietal network connected by the longitudinal fasciculus.
The typical pattern of neglect accompanying right parietal lesions in patients who are left dominant for language has not been observed in __.
Neglect is also less common in __.
non-human primates;
left-handed participants
Two prominent models have been proposed to explain why neglect is more common after right hemisphere damage. According to the representational model, __.
Right hemisphere has attentional representations of right and left
hemispace, while the left hemisphere only represents that right hemispace.
Damage to the left hemisphere doesn’t cause neglect because the right can maintain both on its own.
Two prominent models have been proposed to explain why neglect is more common after right hemisphere damage. According to the attentional bias model, _Under normal circumstances this asymmetry is not obvious, e.g., _.
Left and right hemispheres have natural biases toward attention
contralaterally, but that this bias is slightly asymmetrical with the left hemisphere being more strongly biased toward right hemispace.;
healthy controls will consistently line bisect 1-2% to the left of midline — referred to as pseudoneglect.
Saliency of objects in the neglected hemifield can be impaired. Saliency of objects in the ipsilesional or contralesional visual field can be indexed by __ .
When both types of stimuli are viewed, the typical patterns are of increased probability of eye movements along a spatial gradient from contralesional to ipsilesional location. Suggests that __
the patients’ tendency to look at distinctive, but task irrelevant or task relevant stimuli;
exogenous and goal-driven components of selective spatial attention are equally affected
The __ of ipsilesional stimuli may prevent stimuli from being filtered when task-irrelevant.
abnormally high salience
Saliency of objects in the neglected hemifield is impaired. A spatial lateralised bias is observed even in the absence of __, e.g., eye movements searching for a target in a dark room.
Gaze deviations are observed tonically at rest.
Such biases suggest that __
a stimulus;
those seen during tasks may not reflect just a reduced salience of contralesional space, but also an imbalance in the mechanisms controlling gaze
While sensitivity and responsiveness to behaviourally relevant stimuli improves when moving from contralesional to ipsilesional locations, bias does not reflect abnormal early visual mechanisms, e.g. normal __,
Image segmentation of low-level visual features __ is intact (they see figure ground illusions that require __).
contrast sensitivity;
-in the neglected visual field;
input from neglected side
While sensitivity and responsiveness to behaviourally relevant stimuli improves when moving from contralesional to ipsilesional locations, bias does not reflect abnormal early visual mechanisms, e.g. unconcious processing of neglected information: reaction times to a visual stimulus in the intact field can be modulated by __.
Occipital cortex responds to visual stimuli even under __.
the presence of an undetected stimulus in the affected region of space;
extinction parameters
An alternative explanation of unilateral spatial neglect is that the deficits may not be primarily spatial in nature. Hence why frontal and temporal regions contribute to neglect syndrome (basically the disconnection hypothesis).
Three key non-spatial deficits may account for neglect: __
- Re-orienting of attention
- Detection of behaviourally relevant stimuli
- Arousal and vigilance
Neglect Patients were given the Posner Cueing task. Valid cues resulted in faster reaction times, irrespective of which hemispace the target stimulus appeared. Invalid cues slowed reaction times generally (as per controls), but an interaction
effect was present, with reaction times significantly greater when the invalid cue directed attention to the ipsilesional hemispace.
Interpreted to reflect an ‘extinction’ type effect. Posner’s 3-stage model: __
- Disengagement of attention from current focus
- Movement or shifting of attention to a new location or object
- Engagement of attention on the new location
Right hemisphere and neglect patients show deficits in __ in even the simplest paradigms.
Simple auditory detection tasks show slower RT following right, rather than left, hemisphere damage
Such slowing could reflect __, although the latter effects can be seen following sufficient damage in either hemisphere (or
bilaterally).
target detection;
deficits in arousal and processing capacity
Attentional blink is __
the phenomenon that the second of two targets cannot be detected or identified when it appears close in time to the first.
\_\_ stroke patients with neglect, and those without, show significantly longer attentional blink than controls. \_\_ worsens the blink further. All stimuli in this study were presented centrally (no spatial effect).
RH;
Neglect
Right hemisphere and neglect patients show deficits in arousal and __. Patients with __, showed reduced galvanic skin response to electrical stimulation.
Patients with RH damage show sustained attention problems on elevator counting test.
RH patients who also showed neglect were significantly worse at __.
sustained attention performance;
RH damage, but not left;
sustained attention than those who didn’t have neglect
Effortful maintenance of tonic alertness (sustained attention) over prolonged periods to both hemifields relies on the __, whereas phasic alerting by salient external events depends instead on ascending thalamic —mesencephalic
projections (which should be intact post-stroke), i.e. the low-road.
Hence, should be possible to phasically activate __ in neglect patients, through alerting events (e.g., warning tones). This should __.
Results confirmed the hypothesis that part of what is driving neglect is __.
right fronto-parietal circuit;
what remains of right lateralised cortical networks for attention and alertness;
effectively shift spatial attention leftwards in neglect patients, thus compensating for their deficits;
a change to the overall attention system. It’s typically biased towards sustained attention (fronto-parietal circuit). Neglect stems from damage to this circuit.
The primary spatial impairment in neglect patients is __.
The spatial deficit is observed both at rest and during task performance.
The spatial deficit appears to reflect __.
a failure to attend to the contralesional side of space within a reference frame centred on the observer;
tonic and task-evoked interhemispheric imbalances of activity in right lateralised ‘dorsal’ attention network
The right hemisphere dominance of neglect primarily reflects the laterality of __, rather than the laterality of mechanisms for __.
nonspatial mechanisms for reorienting, detection and arousal in right ventral frontoparietal cortex;
spatial attention
Damage to right frontoparietal cortex in neglect patients impairs __ and hypoactivates the right hemisphere, which unbalances __.
nonspatial functions;
the activity of the sustained attention network.
