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CLPS 0450 > Spatial Attention > Flashcards

Spatial Attention Flashcards

Lectures: 9/29-10/13

1
Q

Describe 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

What are some traits of attention?

A
  • Alertness
  • Concentration
  • Selectivity
  • Control
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3
Q

Why do we need Attention?

A

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

  • Attention selects the stimuli that should be further processed
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4
Q

Describe the difference between early and late selection

A

Early Selection
- Processes that occur early on

ex. hear a noise when driving

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5
Q

Describe Late Selection

A

Selectivley ignoring stimuli to selectivley focus on a certain stimulus
- ex. looking for a street wign when driving

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6
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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7
Q

What does the pop-out effect say about feature binding?

A

A sinlge trait of a stimuli allows it to pop out quickly despite the set size

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8
Q

What does conjunction search say about feature binding

A

Spotlight of attention searches each item serially to bind features
- ex. look for the blue t in a set size of many orange T’s/L’s and blue L’s

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9
Q

Describe the Ventral stream

A

Primarily concerned with identifying what an object is
- Where objects are bound

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10
Q

Describe the Dorsal stream

A
  • Specialized for spatial processing
  • Attending to and acting on objects
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11
Q

How is the salience map of space organized?

A

Topographically

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12
Q

Where is the salience map of space located?
what does it do?

A

located in the parietal cortex
- allocates spatial attention to intergrate or bind visual information
- Re-enterant feedback; spotlight metaphor
- binding of “what” with “where”

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13
Q

what is the object discrimination task?
what does it reveal?

A

asks subject to distinguish between two objects, and choose the non-novel object

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14
Q

what is the landmark discrimination task?
what does it reveal?

A

Monkey has to choose the well that is closest to the stimuli, test spatial location.
- Monkey with lesion in ventral stream had issues with spatial location

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15
Q

Describe Bailnt’s Syndrome
- what parts of the brain are damaged
- what are the symptoms?
- what does it mean to be lost in space?

A

Bilateral Parietal lobe damage
Patients are “Lost in Space”
- Representing space
- Acting on space
- Allocating spatial attention

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16
Q

Describe Agnosia

A

Inability to distinguish between objects

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17
Q

Descirbe the lived experience of Private M. Holmes, who had bilateral lesions of the parietal lobe

A
  • Normal visual percpetion
  • Could see and recognize objects
  • Could not determine location of objects
  • Could not accuratley reach out to grasp objects
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18
Q

What are the Hallmark Charactersistics of Balint’s syndrome?

A
  • Simultanagnosia
  • Optic Ataxia
  • Ocular Apraxia
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19
Q

What is Simultanagnosia?

A
  • Impaired awareness of multiple visual objects or whoel scene
  • Can recognize single objects but cannot compute spatial relationship between objects
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20
Q

What is optic ataxia?

A
  • Impaired reaching behavior under visual guidance
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21
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

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22
Q

Describe a test for optic ataxia
What types of errors could be observed?
What double dissociation might be observed with agnosia vs. optic ataxia patients?

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

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

Optic Ataxia Patients = Can tell you orientation of stimuli, but cant act according to orientation

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23
Q

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

A

A 25 year old woman with carbon monoxide poisoning, that resulted in visual agnosia.

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

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24
Q

Describe the ventral vs. dorsal paths in terms of patient DF & RV

A

Ventral path
- Object perception
Ventral stream impairment
- Conscious perception problem, but intact action ability

Dorsal Path
- Object action
- Impaired action ability, normal conscious perception

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25
Q

What is Ocular Apraxia?

A
  • Fixation of gaze without primary motor deficit
  • Impaired ability to voluntarily shift gaze towards visual stimuli
26
Q

Describe the grabbing and estimating experiment

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

A

Visual Agnosia (DF)
- Normal = Grasp Calibration
- Poor = Manual estimation

Optic Ataxia (RV)
- Poor = Grasp Calibration
- Normal = Manual estimation

27
Q

How does Ocular Apraxia affect fixation patterns?

How can you evaluate whether someone might have Chaotic fixation patterns?

A
  • Chaotic fixation patterns
  • Failure to fixate on informative regions (irrelevant perceptual details capture gaze, which leads to erratic fixation patterns)

Healthy subjects eyes track along with the facial features of a given stimuli vs. Patient IR whose eyes track in an unorganized manner

28
Q

Why do the what and where pathways interact?

A

To allocate spatial attention to integrate or bind visual information

29
Q

How do the where and what interactions integrate and bind visual information?

A
  • Re-entrant feedback
  • Prevent illusory conjunctions
  • Less critical for stored object representations (ex. a yellow banana)
30
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?

A

He has nearly symmetrical bilateral parietal-occipital damage

31
Q

What task tested illusory conjunctions?
How did patient RM perform on this task?

A

Feature binding task
- He could only see one stimulus at a time
- He misbound the features of an the stimulus

32
Q

Patient GK suffered two strokes at age 48, that resulted in bilateral parietal lesions.
How did he respond to the following questions?

1) Are the small circles at the top or bottom of the oval shape?

2) Are the eyes at the top or the bottom of the face?

A

1) 50% accuracy
2) ~90% accuracy

His FFA area was activated to perceive the circles as eyes

  • when circles were changed to squares he could not perceive them as faces - lines for a nose and mouth had to be added
33
Q

What do gestalt grouping effects on extinction reveal?

A

One item trials
- could accurately describe features despite strong or weak grouping

Two items trials
- The stimulus that went extinct was the weak grouping
- He saw the strong group

34
Q

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

A

Unilateral parietal lobe damage

Usually seen in patients with right parietal damage

35
Q

What does right parietal damage lead to?
Which side o

A

Right parietal damage = Neglect on the left side of space

  • Left parietal damage leads to milder symptoms
36
Q

What are the Clinical Characteristics of Neglect Syndrome?

A

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

37
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
38
Q

Describe extinction to simultaneous stimuli?

A

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

39
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

40
Q

Describe Allesthesia

A
  • Pain referred to the non-neglected side of the body
41
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

42
Q

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

A

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

43
Q

Why is Hemi-neglect not a Sensory Disorder?

A
  • Objects in neglected space activate the appropriate visual regions in occipital lobes
  • Neglect affects auditory and tactile judgements as well as vision
  • Phenomenon of visual extinction suggest different perceptual representations are competing for attention (& visual awareness)

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, where even with non-neglected arm – patients showed neglect

44
Q

Describe why Hemi-neglect might be an attentional disorder

A
  • Line bisection test

Hemi-neglect patients are impaired in disengaging and moving attention 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.

45
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
46
Q

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

A
  • Right hemisphere controls shifts of attention to both left and right space
  • Left hemisphere controls attention to only right space
  • RH damage will impair attention to left space, while LH damage can be compensated
47
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

A

1) asymmetrical
2) actually damaged in neglect

48
Q

Describe the Dorsal attention network

A
  • Preparatory and voluntary goal-directed spatial attention
    -Bilateral distribution (not symmetric)
49
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)
50
Q

Where is the ventral attention network located?

A
  • Lateralized to the right hemisphere
51
Q

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

A

The ventral attention network

52
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

53
Q
A
54
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

55
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

56
Q

What is perceptual neglect?

A
  • The inability to attend to visual, auditory, or olfactory stimuli in the contralesional side of the perceptual domain
57
Q

What is representational neglect?

A
  • The inability to represent, describe, or explore the contralesional side of a mental image
58
Q

Describe the relationship between Perceptual and Representational neglect

A

RN is almost always observed in association with PN

59
Q

Describe the traits of the relationship between PN and RN

A
  • Both represent core deficits of neglect
  • But a few dissociations have been observed
60
Q

What is a factor that might

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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