Lecture 2: Attention and Spatial Behaviour

Question 1

What is attention?

Answer 1

the cognitive process of SELECTIVELY CONCENTRATING on one aspect of the environment whilst ignoring other things

this heightens your sensitivity to the stimuli

Question 2

What are the two processes of attention regulation?

Answer 2

Bottom up: arousal - are you awake? ascending reticular activating system

Top down: attention - are you attending this? - prefrontal, parietal

Question 3

How is the ascending reticular activating system involved in the bottom up modulation of attention?

Answer 3

ARAS

• reticulothalamocortical pathway
• transmitter-specific extrathalamic pathways

Question 4

What is the reticulothalamocortical pathway?

Answer 4

Contributes to the bottom-up modulation of attention

• activates cortical arousal by facilitating the transthalamic passage of sensory information towards cerebral cortex.

Uses ACh for the reticulothalamic component and excitatory amino acids along the thalamocortical part.

Question 5

What is the Transmitter-specific extrathalamic pathway

Answer 5

Contributes to the bottom-up modulation of attention

Originates in the brainstem and basal forebrain and directly projects to cerebral cortex.

dopaminergic, serotinergic and noradrenergic…

modulates disposition for the cortex to react.

Question 6

According to Posner (1995), what does attention consist of?

Answer 6

1. Orienting - turning sensory organs (e.g., eyes) toward a stimulus, spreading additional cortical activation to regions associated with processing that stimulus, and inhibiting other activation
2. Controlling contents of consciousness - employing unconscious mechanisms to focus attention onto conscious awareness… for how long etc.
3. Maintaining alertness -

Question 7

6 main factors of attention?

Answer 7

• Arousal
• Capacity
• Selection/focus •Direction/movement/control •Sustaining/vigilance •Valuation/appraisal of stimulus

Question 8

How is attention localised in the brain?

Answer 8

It is not localised in a specific region, instead, it involves a distributed network of regions.

3 main networks:

• Orienting network
• Alerting network
• Executive attention network

Question 9

What is unilateral neglect?

Answer 9

• aka visual or spatial neglect.
• patients ignore left half of their visual field (no conscious perception)
• damage to right angular gyrus of inferior parietal lobe - usually from superior MCA infarct
• unaware of the problem usually

Question 10

What is anosagnosia

Answer 10

lack of insight

Question 11

What is some evidence of a space-based account of attention for neglect?

Answer 11

when patients were to imagine seeing the piazza del duomo in milan, they decribed features on the right side

but when asked to imagine they were standing on the opposite end, they mentioned things that were previously on the neglected side

Question 12

What is evidence of an object-centred account of attention for neglect?

Answer 12

When shown an object, patients only perceived the side on their right.

but when they twist this object around, they could then see the right side which was now on the left, then the new half on the right..

aka could see both sides of object.

WE BELIEVE IN THIS MORE NOW

Question 13

What is Balint’s syndrome?

Answer 13

seen in patients with bilateral parietal damage

Spatial disorder of attention (also includes simultanagnosia and optix apraxia)

incapable of joining visual stimuli - can only see one thing at a time and cannot localise the object to grasp it with their hands

functionally blind because they cannot locate an object that they perceive in space, or tell whether it is moving away or towards them.

Question 14

What is simtultanagnosia

Answer 14

the inability to see more than one thing at once

Question 15

what is optic apraxia

Answer 15

sticky visual fixation

difficulties voluntarily moving eyes to move fixation

it is ATAXIA where there is an inability to reach towards the correct location to the perceived object.

Question 16

What is perception?

Answer 16

the acquisition and processing of sensory information in order to see/hear/taste/feel the objects in the world

combines visual stimuli with previous knowledge.

Question 17

Hierarchical model of object recognition

Answer 17

??

Question 18

what is perceptual segregation

Answer 18

refers to the notion that the human visual system is design to impose organisation on the visual environment

seperates figure and ground

when the two are ambiguous (can be reversed), the perceptual system only allows us to see one at a time.

Question 19

What is an agnosia

Answer 19

object recognition disorder

can be apperceptive or associative

Question 20

What is an apperceptive agnosia?

Answer 20

Deficit in object recognition resulting from perceptual processing.

• Occipito-temporal damage
• difficulty distinguishing visual shapes
• but can recognise objects using cues (relative size, texture, colour) and then infer what the object is based on these cues…
• example: picture of woman washing dishes and kids stealing cookies - could only see black lines on a white background
• cant copy drawings very well if asked, but can draw better if drawn freehand (Recall from memory what an item looks like. eg. glases)
• basic visual functions intact

Question 21

What is an associative agnosia?

Answer 21

Deficit in object recognition resulting from problems involving visual memory representations.

• can be category specific

Question 22

What is integrative agnosia?

Answer 22

A type of apperceptive agnosia

can perceive components of an object, but cant integrate them to make a whole.

example: part change thing

Question 23

Describe object constancy impairments

Answer 23

• right parietal damage

- deficits in recognising objects presented in unusual views, but are fine with usual views.

Question 24

What is object constancy

Answer 24

the ability to recognise objects from different viewpoints and under different lighting

it’s theorise that we store a canonical representation of the object in memory, then rotate the visual image to match it

Question 25

What is object orientation agnosia?

Answer 25

Patients can name objects, but can’t determine whether they’re in the correct orientation or decide whether two objects are in the same orientation.

right parietal damage

can copy drawings, but rotate it

evidences that recognition system is insensitive to orientation.

Question 26

What is optic aphasia

Answer 26

deficits in naming visually presented objects after a LEFT OCCIPITO-TEMPORAL LESION

• Can pantomime (so not apraxic) how to use the object and can name it based on verbal definitions and tactile manipulation (hence diff from anomia).
• because they can pantomime, they have semantic access. this threatens the hierachical model.
• maybe the semantic system is modality specific.

Question 27

What is the difference between associative agnosia and optic aphasia?

Answer 27

Optic aphasics can recognise objects non-verbally, and sort them visually by category. They have more semantic ability than associative agnosia patients, who have lost the ability to link stored semantic information to what they see.

Associative agnosia patients are very sensitive to quality of stimulus and perform better on real objects than images, where as optic aphasics do not

optic aphasics make semantic errors, where as associative agnosic patients tend to make visual errors.