Attentional Disorders

Question 1

Is attention primarily associated with the parietal lobes?

Answer 1

No, attention is controlled by a network of interacting structures that are distributed throughout the brain and have overlapping functions.

Question 2

Which lobe of the brain did we consider in regards to attention disorders?

Answer 2

The parietal lobes

Question 3

What attentional disorder would you expect from a unilateral parietal lesion?

Answer 3

Hemispatial Neglect

Question 4

What attentional disorder would you expect from bilateral parietal lesions?

Answer 4

Bálint’s syndrome

Question 5

Which hemisphere is a lesion to the parietal lobe more likely to cause hemispatial neglect?

Answer 5

Hemispatial neglect is most common, severe and persistent after damaging the right hemisphere, especially the inferior parietal lobe.

Question 6

Which vascular territory is involved in parietal lobe damage/hemispatial neglect?

Answer 6

Middle Cerebral Artery

Question 7

What is hemispatial neglect? And does it only effect visual systems?

Answer 7

Hemispatial neglect refers to a failure to become aware of or orient toward the contralesional environment or side of the body.
It can include:
- Tactile Neglect
- Visual Neglect
- Auditory Neglect
- Motor Neglect (directional hypokinesia or reduced use of contralesional limb)

Question 8

Patients with hemispatial neglect will bisect lines to which side of true centre?

Answer 8

Patients with neglect bisect lines ipsilesional of true centre.

Question 9

Regarding line bisecting and hemispatial neglect, what happens as the length of the line increases?

Answer 9

The ipsilesional bias increases with the length of the line.

Question 10

How do you determine whether line bisection bias relates to visual or motor neglect (e.g. directional hypokinesia)?

Answer 10

Task: Circle the end of the horizontal line that is closer to the vertical mark.
If the rightward bisection errors of a neglect patient are due to a rightward motor bias (e.g. directional hypokinesia) subjects would be expected to point generally to the right.
However, most patients will circle to the left, suggesting a perceptual deficit. The subjects are perceiving the left half of the line as shorter.

Question 11

Are hemispatial neglect and hemianopia the same thing?

Answer 11

No. Visual neglect and visual field deficits commonly co-occur after unilateral brain damage such as stroke. The conditions, however, are recognised as operationally and conceptually distinct.

Question 12

What are the differences between hemispatial neglect and hemianopia?

Answer 12

Someone with hemianopia knows they can’t see one side of their visual field and they’re moving their heads around trying to see.
Patients with neglect are unaware of their deficit, their imagination space is gone on that side too. It’s the representation of space, not simply visual.

Question 13

What is extinction?

Answer 13

Patients are aware of contralesional stimulation when it occurs alone, but fail to notice it when it occurs together with ipsilesional stimulation.
Ipsilesional stimulation competes with contralesional stimulation such that the contralesional stimulation is extinguished from awareness.

Question 14

What is extinction usually associated with?

Answer 14

Hemispatial neglect

Question 15

What was the purpose of Extinction Experiment 1?

Answer 15

To find out to what extent does contralesional extinction depend on the ipsilesional and contralesional items sharing visual features.
Detangling visual differences from meaning/response differences.

Question 16

What was the Extinction Experiment 1? (general methods)

Answer 16

Task: Read the items, then report what you saw on each side.
Stimulus conditions:
- Identical (e.g., ONE - ONE)
- Visually different but same meaning/response (e.g., ONE - 1)
- Visually different and different meaning/response (e.g., ONE - TWO)

Question 17

What did we learn from the Extinction Experiment 1?

Answer 17

At least as much extinction occurred for ONE-1 as ONE-ONE.
Suggesting that extinction is determined by competition at a semantic or response level, rather than at an early visual level.

Question 18

What was the purpose of Extinction Experiment 2?

Answer 18

Does contralesional extinction depend on the ipsilesional and contralesional items sharing the same meaning or response?
So detangling meaning and response.

Question 19

What was the Extinction Experiment 2? (general methods)

Answer 19

Task: Read the items, then report what you saw on each side.
Stimulus conditions:
- Identical (e.g., ONE - ONE)
- Visually and semantically different but same response (e.g., ONE - WON)
- Visually different and different meaning/response (e.g., ONE - TWO)

Question 20

What did we learn from the Extinction Experiment 2?

Answer 20

Homophones (e.g., ONE - WON) were extinguished as much as identical items (e.g., ONE - ONE), suggesting that extinction is determined by competition at a response level, rather than at a visual or semantic level.

Question 21

To what extent do you think extinguished stimuli are processed?

Answer 21

There must be some processing in the brain, or it wouldn’t matter what the stimulus looks like.

Question 22

Unconscious Processing of Extinguished Stimuli: An fMRI Single Case Study of Extinction. What did this tell us?

Answer 22

These findings suggest that the same neural machinery was activated in early visual areas of the right hemisphere by a left visual field stimulus, whether seen or extinguished.

Question 23

How can the flanker task be redesigned to enable comparison of distractor processing in the impaired hemifield versus the healthy hemifield?

Answer 23

Instead of making distractor appear above or below, move the distractor to either the left or the right.

Question 24

Regarding the Flanker Task in patients with Extinction, What was the task?

Answer 24

Report the color (red or green) of:

• Peripheral report (target = peripheral stimulus)
• Central report (target = central stimulus)

Question 25

Regarding the Flanker Task in patients with Extinction, What was the purpose of the peripheral report?

Answer 25

How bad their attentional bias was, verify this.

Question 26

Regarding the Flanker Task in patients with Extinction, What was the purpose of the central report?

Answer 26

To what extent does the distractor impact reaction time.

Question 27

Regarding the Flanker Task in patients with Extinction, What were the findings?

Answer 27

• Peripheral Report:
  RTs to contralesional targets were much slower than RTs to ipsilesional targets
  Strong bias toward ipsilesional hemifield
• Central Report:
  A compatibility effects occurred, however, the magnitude of the compatibility effect did not depend on the distractor side (ipsi or contralesional).

So the extinction does not translate to less impact of the distractor.

Question 28

Do patients recover from hemispatial neglect?

Answer 28

Recovery from hemispatial neglect can take weeks to months, and some patients exhibit a permanent deficit in contralesional attention.

Question 29

Was there a line bisection bias in patients with chronic unilateral parietal damage? (who had recovered in a clinical sense and had performed cancellation task perfectly)

Answer 29

Yes, a significant bias, however not large.

Question 30

What are the three effects we discussed regarding unilateral parietal damage?

Answer 30

• hemispatial neglect
• extinction
• chronic deficits

Question 31

Where are the lesions that cause Balints syndrome?

Answer 31

Bilateral lesions of the posterior parietal lobes or parieto-occipital junction

Question 32

What are the two cardinal features of Balints syndrome?

Answer 32

Simultaneous agnosia: impaired ability to become aware of more than one object at a time.
Spatial disorientation: deficit in mentally representing space and directing actions toward objects in the visual scene (including optic ataxia).

Question 33

What reduces simultaneous agnosia?

Answer 33

Connectedness and familiarity.

Question 34

What is optic ataxia?

Answer 34

Difficulties reaching and grabbing accurately