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CLPS 0450 > Spatial Attention COPY > Flashcards

Spatial Attention COPY Flashcards

Lectures: 9/29-10/13

1
Q

Define Attention

A

A set of processes that interact with other processes in the performance of different perceptual, cognitve, and motor tasks

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2
Q

Why do we need Attention?

A

We have a limited capacity to process all information based on relevance to current goals

  • Attention filters information -> allows only some information to enter into consciousness
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3
Q

Define early selection theory

A

We never actually process information that we are not attending to

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4
Q

Describe Late Selection theory

A

All information gets processed up to a point, but it does not get further processed unless its really important

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5
Q

Describe the spotlight metaphor of spatial attention

A
  • May move from one location to another
  • Can zoom in & out; have a narrow or wide “beam”
  • Attended location not necessarily same as where eyes are fixated
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6
Q

Define the Ventral route

A
  • “What” an object is
  • Processing finer details like shape, color, texture
  • Goal = object recognition
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7
Q

Describe the Dorsal Route

A
  • “How/where” spatial processing
  • Detecting the coarse strucutre of the world and how we are moving through it
  • Sensitive to motion and scale
  • Goal = control and direct movement/action
    acting on objects
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8
Q

What route does an object discrimination task involve?

monkey is rewarded for choosing triangle

A

Ventral Route

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9
Q

What route does a landmark discrimination task involve?

monkey is rewarded for choosing object closest to right handside

A

Dorsal Route

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10
Q

Why do the what and where pathways interact?

A

To allocate spatial attention to integrate or bind visual information

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11
Q

What does Saliency map help do?
What does it bind?

A

Helps us allocate spatial attention to intergrate or bind visual information

Binds what and where; binds multiple features
- Object is red AND horizontal

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12
Q

Describe pop out search vs. conjunction search

How does this relate to the Salient Map structure?

A

Pop out search
- Blue T captures attention in pool of Red Ts
- Time does not change according to set size
- No feature binding

Conjunction
- Looking for a conjunction of features
- Time it takes to find stimulus does increase with set size

Salient Map
- Serial search is due to the topographic nature of salience map
- Attention is binding the features of each stimulus one by one

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13
Q

How is the salience map of space organized?

A

Topographically

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14
Q

Describe Agnosia

A

Inability to distinguish between objects

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15
Q

Define illusory conjucntions

What parts of the brain are typically damaged in patients that have th illusory conjunctions?

A

Illusory conjunctions
- Sloppy binding of features

Damage
- Dorsal stream
- Bilateral-occipital damage
- Parietal cortex

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16
Q

Patient RM was a 54 year old man who suffered two strokes.

After the strokes he was impaired in binding objects under certain conditions.

Where what parts of his brain were damaged?

What was a visual condition he suffered from?

A

Damage: He had nearly symmetrical bilateral parietal-occipital damage

Condition: Illusuary conjunctions

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17
Q

Describe Illusary conjunctions

A

Sloppy binding of features

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18
Q

Describe the Private M who had bilaterial lesions of the parietal lobe

What could he do?
What couldnt he do?

A

Able to
- See and recognize objects

Unable to
- Determine the location of objects
- Accuratley reach out to grasp objects

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19
Q

What what area of brain damage is associated with Balint’s Syndrome? What stream is associated with this syndrome?

A

Bilateral damage to parietal lobe
- Dorsal stream

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20
Q

What are the Hallmark Charactersistics of Balint’s syndrome?

A
  • Simultanagnosia
  • Optic Ataxia
  • Ocular Apraxia
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21
Q

Define optic
Define ocular

A

Optic = sight
Ocular = relates to eye

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22
Q

Define ataxia
Define apraxia

A

Ataxia = inability to coordinate
Apraxia = inability to carry out skilled movement

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23
Q

What is Simultanagnosia?

A
  • Impaired ability to percieve multiple objects at once or their spatial relations (see one object at a time)
  • Therefore cannot percieve spatial relations between obejcts
  • When second object is introduces, the first object is extinguished
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24
Q

Describe a test for Simultagnosia

A

Patient is asked what they can see
1) can see a comb and a spoon individually
1) can not see the objects together, can only see the comb or the spoon seperatley

25
Q

How do patients cheat Simultanagnosia?

What experiments are associated with this cheating?

A

By using stored object representations within-object spatial relations.

!!!Dorsal Ventral Interaction!!!

FACE SHAPE EXPERIMENT
- Using stored representation of faces to know if eyes are at top or bottom of “face” that is actually circles within a circle

GESTALT GROUPING
- Strong visual vs. weak visual groups influence the stimulus that a patient attends to

26
Q

What is optic ataxia?

A
  • Impaired reaching behavior under visual guidance
27
Q

Describe a test for optic ataxia
What types of errors could be observed?

A

Patient is asked to put their hand through a slot in a board. The patient could not put hand in slot successfully.
- Orientation errors
- Direction errors

28
Q

What double dissociation might be observed with agnosia vs. optic ataxia patients?

What stream damage is associated with each type of damage?

A

Agnosia Patients = Can’t consciously describe an orientation of stimuli, but are able to act as if they understand the orientation (Ventral Damage)

Optic Ataxia Patients = Can tell you orientation of stimuli, but can’t act according to orientation (Dorsal Damage)

29
Q

Describe Patient DF
What was her diagnosis?
What stream was she impaired in?
What skill was she normal at?
What skill was she impaired in?

A

A 25 year old woman with carbon monoxide poisoning.

Diagnosed with VISUAL AGNOSIA

Impaired in VENTRAL STREAM

Normal = Visuomotor Posting

Impaired = Orientation Matching (often turns it the opposite way)

30
Q

In the grabbing and estimating experiment patients are asked to
1) pick up an ibject using finger and thumb
2) estimate length of object ising finger and thumb

How does a patient with Visual Agnosia perform on this task vs. a patient with optic ataxia?

A

Visual Agnosia (DF)
- Normal = Grasp Calibration (intact dorsal stream to act on object)
- Poor = Manual estimation

Optic Ataxia (RV)
- Poor = Grasp Calibration
- Normal = Manual estimation (intact ventral stream to percieve features of obejcts)

31
Q

Describe the 3 impairments associated with ocular apraxia

A

1) Inability to move eyes voluntarily to points in visual field
2) “Sticky Fixation” inability to disengage in fixation
3) Inability to maintain

32
Q

What is tested to diagnose a patient with Ocular Apraxia?

A
  • Chaotic fixation patterns are assessed -> they are not as selective to semantically meaningful information
33
Q

What area of the brain is damaged to result in neglect syndrome?

Neglect is usually seen in patients with ____ parietal damage?

A

Unilateral parietal lobe damage

Usually seen in patients with right parietal damage

34
Q

What does right parietal damage lead to?
Damage on what side of the brain leads to milder neglect symptoms?

A

Right parietal damage = Neglect on the left side of space

  • Left parietal damage leads to milder symptoms
35
Q

What are the Clinical Characteristics of Neglect Syndrome?

A

1) Hemispatial Neglect
2) Extinction to Simultaneous Stimuli
3) Hemiakinesia, Motor Exctinction Impersistence

36
Q

Describe Hemi-spatial Neglect?

A
  • Fail to report or respond to stimuli
  • Neglect of hemispace when asked to perform tasks
  • Fail to recognize contralateral extremities as their own
37
Q

Describe extinction to simultaneous stimuli?

A

Multiple stimuli compete with each other and leads to the extinction of one stimuli

38
Q

Describe Hemiakinesia, Motor extinction and Impersistence

A

Neglect syndrome is not visual – also extends to motor function.
- Patients neglect one half of the body

39
Q

Describe Allesthesia

A
  • Pain referred to the non-neglected side of the body
40
Q

Describe Anosognosia

A

Unawareness of the deficit
- They see nothing wrong in their world and perceive their world as normal
- The brain creates an illusion of wholeness

41
Q

What are the the three theories on what might drive neglect?

A

1) Primary Sensory Disorder
2) Attentional Disorder
3) Representational Disorder

42
Q

Why is Hemi-neglect not a Sensory Disorder?
Describe Facts and Tests

A
  • Objects in neglected space activate the appropriate visual regions in occipital lobes
  • Neglect affects auditory and tactile judgements as well as vision

Extinction
- The fact patients can see a stimulus on their neglect side, but then it becomes extinct when a stimulus is presented on their non-neglect side indicates that the patients are able to sense on their neglected side

Neglect is based on midline of body NOT fixation point
- Neglect is not Heminopia

Burning house experiment: when presented with a regular house and burning house patient chose to live in the regular house 81% of the time.
- This means - that the ventral stream continues to process neglect objects up to the stage of object recognition and possibly semantics

Findings from the Tactile Maze Experiment: Even when searching maze with with non-neglected hand – patients showed neglect to side associated with damage

43
Q

Describe why Hemi-neglect might be an attentional disorder

Tests?
What does this indicate about the deficiency of

A

Extinction
- The fact patients can see a stimulus on their neglect side, but then it becomes extinct when a stimulus is presented on their non-neglect side indicates that the sides are compeneting for attention

Line bisection test
- Cueing attention by making patient guess a number on the neglected side aids in accurate line bissection

Valid vs. Invalid Cue Test
- RT Valid Side < RT Invalid Side
- Valid = When target and cue are on the same side of space
- Invalid = When target and cue are on opposite sides of space (cue is on good side)

Hemi-neglect patients are impaired in DISENGAGING AND MOVING to a target location!!!

Ex. a patient had damage on the right hemisphere
- The right hemisphere can’t compete with the left hemisphere. it wants to shift attention to the left visual or motor field, but attention is stuck to the right visual field because the unimpaired left hemisphere is dominant.

44
Q

If systems are seemingly symmetrical, why is there a right hemisphere dominance of spatial neglect?

A
  • Might reflect corresponding asymmetry in spatial attention
  • Standard Theory of Neglect
45
Q

What does the standard theory of neglect argue? in terms of right hemisphere dominance

A
  • RH controls shifts of attention to both left and right space
  • LH controls attention to only right space
  • RH damage will impair attention to left and right space, while LH damage can be compensated
46
Q

The problem with the Standard Theory of Neglect is that –there is no clear evidence that the brain network mediating spatial attention is either ___ or ___

A

1) Asymmetrical
2) Actually damaged in neglect

47
Q

Describe the DORSAL ATTENTION network

A
  • Goal directed and voluntary shifts in attention
    -Bilateral distribution (not symmetric)
48
Q

Describe the VENTRAL ATTENTION network

A
  • Detection of salient unexpected stimuli
  • Arousal and vigilance
  • Mediates interruption of attentional focus controlled by the dorsal system (disengagement/reorienting attention)
49
Q

Where is the ventral attention network located?

A
  • Lateralized to the right hemisphere
50
Q

The area of the brain that is damaged in most hemineglect patients is associated with what network?

A

The ventral attention network

51
Q

What is the source of the deficit found in neglect patients?

A

The damage is located in
- The alerting network that stops the shifting of attention to allow the other hemisphere to control attention

SINCE THIS NETWORK IS REPRESENTED MORE IN THE RIGHT HEMISPHERE THAN THE LEFT –> primary neglect in right parietal lobe damage

52
Q

Describe the difference between attentional disorder and representational disorder

A

Attentional Disorder
- Intact representation, but can’t attend to the left half

Representational Disorder
- You cant create the left half of your representation, and therefore cant shift or scan that half of the representation because it doesn’t exist

53
Q

What is representational neglect?

A
  • The inability to represent, describe, or explore the contralesional side of a mental image
54
Q

What did the piazza de Dumo Study argue?

A

Argued that subjects can not create a mental image of their left hemi space and therefore can not attend to it
- When asked to imagine they were standing at a certain position in notable city square they described what they would hypothetically see neglecting things that are on the contra-laterial side
- When in another position they would state they would hypotheticallly see things that they previously neglected

55
Q

What are the two types on neglect?

A

Perceptual Neglect
Representational Neglect

56
Q

Compare and contrast Perceptual and Representational neglect

A

Perceptual neglect patients are unable to attend to vis, aud, ola stimuli on the contralesional side

Representational neglect patients are unable to represent, describe, or explore the contralesional side of their mental images

57
Q

Describe the relationship between Perceptual and Representational neglect

A

RN is almost always observed in association with PN

However PN is not always observed in associattion with RN

58
Q

What is a factor that might explain the asymmetry?

A

Could be due to differential involvement of visuospatial memory

  • RN caused by a deficit in the interaction between working memory and attention
  • Overlap in brain regions mediating RN and PN

CLPS 0450 (9 decks)

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