Neuropsychology: The Attending Brain

Question 1

Why do we need attention?

Answer 1

-Closely related to info processing
-Capacity to process info limited
-Attention helps in selecting relevant and discarding irrelevant info (from internal or external resources)
-Crucial to avoid sensory overload
-Attentional processes lay at interface between external environment and internal state

Question 2

What are characteristics of spatial attention processes?

Answer 2

-Spatial attention: ability to focus on or orient resources to spatial locations
-Different subtypes of orienting
-Posner paradigm

Question 3

What different subtypes or orienting are there in spatial attention?

Answer 3

-Covert orienting: without moving eyes or head
-Overt orienting: moving eyes or head along with focus of attention
-Exogeneous orienting: externally guided by stimulus
-Endogeneous orienting: guided by goals of perceiver

Question 4

What is the Posner paradigm in spatial attention?

Answer 4

-Detecting stimuli without knowing where stimuli will be presented
-Response times higher when spatial cue invalid, lower when spatial cue valid
-Spatial attention can be facilitated (valid cue) or disrupted (invalid cue)
-Disengagement of attention takes time

Question 5

What are characteristics of non-spatial attention processes?

Answer 5

-Non-spatial attention: attention directed to objects, features or in temporal domain
-Face and house as example of object-based attention
-Attentional blink as example of temporal domain attention

Question 6

What kind of example is face and house for object-based attention?

Answer 6

-Presented stimulus contains face and house
-Attention can be directed to either one
-Attention to face increases activation in fusiform face area
-Attention to house increases activation in parahippocampal place area

Question 7

What kind of example is attentional blink for temporal domain attention?

Answer 7

-Fast presentation of letters and numbers where participants have to detect and verbally report letters
-Participants fail to report second letter if appearing soon after first letter
-Limited attentional capacity: T1 takes over capacity limited, so attention for T2 is blinded (attentional blink)

Question 8

What is the general theory of attention?

Answer 8

-Attention affects sensory processing
-Actual attentional processes happen mainly in frontoparietal network

Question 9

How are the parietal lobes involved in attention?

Answer 9

-Specialized for spatial processing and called “where” route
-Bring together different types of spatial representation needed for action (ex.: integrating visual space with body space), also called “how” route
(image)

Question 10

Which parts of the parietal lobes are involved in attention?

Answer 10

-Superior parietal lobule (SPL)
-Inferior parietal lobule (IPL)
-Angular gyrus (Ang)
-Supramarginal gyrus (Smg)
-Temporoparietal junction (TPJ)
-Intraparietal sulcus (IPS): multiple areas
–>Most famous: lateral intraparietal area (LIP)
(image)

Question 11

What are characteristics of the what route or ventral stream for information processing?

Answer 11

-Processing shapes, colors, textures and perception
-Identification of objects, faces and memory of objects
-Includes temporal lobes

Question 12

What are characteristics of the where/how route or dorsal stream for information processing?

Answer 12

-Involves attention in space to objects and acting upon them
-Includes parietal lobes
–>Specialized for spatial processing (where)
–>Bring together different types of spatial representation needed for action (how)

Question 13

What are characteristics do the parietal lobes have in the dorsal where pathway of information processing?

Answer 13

-Lateral intraparietal area (LIP): lateral bank of intraparietal sulcus
–>Important for attention
–>Single cell electrophysiology in monkeys
-Intraparietal sulcus (IPS): divides superior parietal cortex and inferior parietal cortex
–>fMRI evidence in humans
-Fronto-parietal attention mechanisms: where/how (dorsal) stream consists of 2 major attentional networks

Question 14

What were the findings in the single cell electrophysiology in monkeys about the lateral intraparietal area (LIP) in the dorsal where pathway of information processing?

Answer 14

-LIP has motor properties: important for eliciting movements, in particular eye movements (saccades)
-LIP has sensory properties: responds to both sound and vision
–>Enables sounds to me remapped to eye-centred coordinates

Question 15

How is the lateral intraparietal area important for attention?

Answer 15

-Sparseness: doesn’t respond to all sensory stimuli
-Responds more to unexpected stimuli: important for exogenous attention
-Responds more to task/goals relevant stimuli: important for endogenous attention
-Can enable covert and overt orienting (with/without eyes)
-Codes salience map: presenting array of geometrical shapes

Question 16

What evidence was there found in fMRI in humans about the intraparietal sulcus (IPS) about the dorsal where network of attention?

Answer 16

-Orienting cues activate IPS and frontal region (frontal eye field (FEF)) involved in saccades even if no overt motor response needed
-Similar network involved in object-based attention

Question 17

Of what 2 major attentional mechanisms does the where/how dorsal stream consist?

Answer 17

-Dorso-dorsal route (dorsal attention network)
-Ventro-dorsal route (ventral attention network)
(image)

Question 18

What are characteristics of the dorso-dorsal route of the attention network?

Answer 18

-Dorsal attention network
-Including IPS and FEF
-Involved in orienting in salience map
-More bilateral

Question 19

What are characteristics of the ventro-dorsal route of the attentional networks?

Answer 19

-Ventral attention network
-Including temporoparietal junction (TPJ) and ventral prefrontal cortex (VFC)
-Acts as circuit breaker that interrupts ongoing cognitive activity to direct attention outside of current focus of processing (ex: detecting targets, disengagement)
-More strongly right lateralized

Question 20

What are characteristics of hemispheric differences in spatial attention?

Answer 20

-Parietal lobes represent full visual field, but in graded fashion: right parietal lobe (RPL) and left parietal lobe (LPL) show different things
-Brain damage in left and right hemisphere doesn’t result in symmetric effects
–>Brain damage in right parietal lobe more profound effects
–>Possible right IPS contributes more to salience map (natural tendency to be drawn to left)

Question 21

What does the right parietal lobe show in the context of attention?

Answer 21

-Maximal responsiveness to stimuli on far left
-Moderate responsiveness to stimuli in middle
-Weaker responsiveness to stimuli on far right

Question 22

What does the left parietal lobe show in the context of attention?

Answer 22

-Maximal responsiveness to stimuli on far right
-Moderate responsiveness to stimuli in middle
-Weaker responsiveness to stimuli on far left

Question 23

Why doesn’t brain damage on a particular hemisphere result in symmetric effects in the context of attention?

Answer 23

-Damage to RPL: less attentional resources in far left, moderate in middle and near-normal in right
-Damage to LPL: less attentional resources in far right, moderate in middle and near-normal in left
-More severe and persistent neglect of visual field in RPL-damage compared to LPL damage
-Evidence for right IPS to have larger contribution to construction of salience map

Question 24

What are characteristics of hemispheric differences in non-spatial attention?

Answer 24

-Right TPJ (temporoparietal junction) more important in non-spatial attention than left TPJ (Corbetta et al.)
-RPL: important for attending to salient stimulus (Mevorach et al.)
-LPL: important for attending to non-salient stimulus (Mevorach et al.)

Question 25

What theory of attention is there?

Answer 25

Biased competition theory

Question 26

What is the Biased Competition Theory of attention?

Answer 26

-Competition occurs at multiple stages rather than at some fixed bottleneck
-Competition occurs IN PARALLEL at most stages with serial processing linked to motor output stage (ex.: can only fixate at 1 location at time)
-Evidence: parietal lobe damage (extinction)

Question 27

What kind of evidence is extinction for the Biased Competition Theory of attention?

Answer 27

-Inability to perceive multiple stimuli of same type simultaneously
-Clear behavioral symptom that relates to BCT
-Due to brain damage, often in right parietal lobe (RPL)

Question 28

What kind of evidence is right parietal lobe damage for the Biased Competition Theory?

Answer 28

-Related to visual extinction
-Lost ability to be AWARE of contralesional side of space when competitor on ipsilesional side present
-Didn’t lose ability to SEE contralesional side of space, nor ability to orient attention to contralesional side
-NOT same as hemispatial neglect: ignoring stimuli on contralesional side of space

Question 29

What kind of evidence is left parietal lobe damage for the Biased Competition Theory?

Answer 29

-Related to visual extinction and damage to left IPS
-Performs good when target appears in ipsilesional side of space
-Performs good when target appears in contralesional side of space in single valid condition
-Performs bad when target appears in contralesional side of space in single invalid and double valid conditions
-Lesions of parietal lobe impair orienting and re-orienting attention to contralesional side of space

Question 30

What disorders of attention are there?

Answer 30

-Balint’s syndrome
-Hemispatial neglect

Question 31

What is Balint’s syndrome?

Answer 31

-Clinical, clear symptoms: simultanagnosia, optic ataxia, optic/ocular apraxia
-Other, less prominent symptoms: basic visual abilities normal, visual spatial attention problems (unable to locate objects verbally or by reaching and pointing), auditory spatial attention problems (impaired to locate sounds), can state which side of body and which body part touched (probably distinction of body space and external space)
-Neural basis: often bilateral and extensive brain damage in parietal cortex

Question 32

What is simultanagnosia?

Answer 32

Inability to perceive more than 1 object at same time

Question 33

What is optic ataxia?

Answer 33

Inability to reach in proper direction for object under visual guidance

Question 34

What is optic or ocular apraxia?

Answer 34

Failure to make proper eye movements without primary deficit of eye movement

Question 35

What summary can you give of Bálint’s syndrome?

Answer 35

-Simultanagnostic patients can recognize single objects but cannot compute spatial relationships between objects
-But when is object an object: is face object, or several objects
-Evidence suggests that these patients can group several parts into wholes if shared color, shape or connection
-Top-down factors important too (ex: are ovals at top or bottom vs is face correct way up)

Question 36

What is hemispatial neglect?

Answer 36

-Attention disorder
-Failure to attend to stimuli at one half of space
-Unilateral damage to right inferior parietal lobe: RPL more common, but LPL possible, but also homogenous disorder, so multiple regions contribute
-Clinical, clear symptoms: images on contralesional side will not be drawn or have omissions, images transformed so all features of image shown on ipsilesional side, do not cross out objects on contralesional side
-Disorder of attention, NOT low-level perception: not AWARE of stimuli, but visual regions of occipital lobe activated, able to detect objects on contralesional side if cued, multi-sensory problem (affects auditory and tactile judgements and vision), problems with visual extinction
-Different types

Question 37

What kinds of tasks are impaired in hemispatial neglect?

Answer 37

-Drawing from memory
-Cancellation task

Question 38

What different types of hemispatial neglect are there?

Answer 38

-Perceptual neglect: neglect in ability to attend to sensory information
-Representational neglect: neglect in imagination
-Near space/peripersonal neglect: problems with line bisection using pen and paper, visual search of external objects impaired
-Far space neglect: problems with line bisection using projected image and laser pointer
-Body space/personal neglect: failure to groom contralesional part of body or notice position of limbs
-Object-based/allocentric neglect: problems with contralesional side of objects
-Space-based/egocentric neglect: problems with contralesional side of space
-Neglect dyslexia: problem with reading contralesional side of sentences, words and/or letters (dependent on object- or space-based neglect), right brain damage problems with first letter, left brain damage problems with last letter

Question 39

What are the differences between hemispatial neglect and blindsight?

Answer 39

-Lack of awareness
–>Hemispatial neglect: not restricted to vision and may be found for other sensory modalities
–>Blindsight: restricted to visual modality
-Processing
–>Hemispatial neglect: objects may be processed implicitly
–>Blindsight: implicit knowledge restricted to basic visual discriminations (direction of motion)
-Overcoming lack of awareness
–>Hemispatial neglect: by directing attention to neglected region
–>Blindsight: not overcome by directing attention to blind region
-Eye movement
–>Hemispatial neglect: failure to voluntary move eyes to neglected region
–>Blindsight: eyes move to blind region
-Neglected/blind region
–>Hemispatial neglect: neglected region egocentric or allocentric
–>Blindsight: always retinocentric