Lec 8

Question 1

Model of attention

• Early vs. late selection
• Multi-level filtering system

Answer 1

Early vs. late selection.

• Early selection or early with adaptable filter system: distractors may/may not be processed
  
  • Attention helps with early selection (ex. I pay attention to the words, ignore the sounds)
  • Adaptable filter system (ex. graded filters)
• Late selection: cognitive resources req’d to suppress distractors
  
  • Attention may be used in late selection
  • Even though you are not aware of this stimulus -> it is still processed
    
    • Exp: show attention blink words (flashes of words)
    • There’s EEG activity
• Multi-level filtering system (early and late selection) - orange

Question 2

Model of attention

• Nilli Lavie – Load theory of attention & Cog control
  
  • perceptual load & distraction processing
  • cog load & distraction processing
    *

Answer 2

• Nilli Lavie – Load theory of attention & Cog control
  
  • Describes how attentional resources are allocated to tasks that are more or less difficult on diff lv
  • Perceptual load vs cog load (ex. # of #s)
    
    • High perceptual load (difficult to see) -> distractors are not processed = early selection
    • Low p load -> distractors processed, cog resources required to surprise = later selection
      
      • Ex. easy to find target = OROOO -> low p load
      • Ex. difficult = MXHKZW -> high p load
    • Scenario: ppl talking when you are doing a low p load task is more distractor as you have more resources to attend to other things
    • Scenario
      
      • In fMRI machine
      • # 1: Presented a stimulus (face and a string of letters)
      • # 2: determine: Is there a “Z”?
      • Seeing the face -> activate amygdala (process fear)
      • Graph: when there is low perceptual load -> distractors (face) is processed -> more amygdala activation; vv
    • High cog load -> distractors are not suppressed (less resources to suppress)
    • Scenario
      
      • # 1: Presented a stimulus (face and a string of #s)
      • # 2: need to remember short (lo c load) or long # (hi c load)
      • Results: high cog load (lots of #s) -> more activation in FFA due to distracting face
      • IOW effects of cog load is opp of p load
• Low p load -> strong response to face (distractor not processed)
• High p load -> low response to face (distractor processed)
• Low cog load -> low response to face (more resource to suppress distractor)
• High cog load -> high response to face (less resource to suppress distractor)

Question 3

Model of attention

• “Spotlight” model
• zoom lens model
• combine the spotlight model w/ zoom lens model
• 2 Problems with spotlight and zoom lens models
• fMRI experiment → 5 RSVPs tasks
• Exp: multiple object tracking

Answer 3

• “Spotlight” (or search light) model: attention is confined to a coherent region of space and can move from one point to the next.
  
  • IOW attention = spotlight (better perception, responses)

Cueing as a tool for examining attention

• “Zoom lens” model: attention expands from fixation…grows to fill whole region…shrinks to include just cued location
  
  • IOW: you can pay attention to a whole region, our zoom your focus to a specific location
• X
• When we combine the spotlight model w/ zoom lens model of attention: you have a spotlight, and you can zoom in/out
• Problems with spotlight and zoom lens models:
• 1. Attention shifts rather instantly.
     * Ex. when you change spotlight from A to B, we should be paying attention to nothing (space b/w)
     * What happens is that, attention “jump” from A to B
• # 2: Attention can split into more than one focus; not necessarily coherent region in space.
  • e.g., fMRI experiment
    
    • 5 RSVPs tasks – letter will appear in those locations (red dots)
      
      • Ex. If you see “K” you need to press a button
    • # 1: fixate at the centre dot
    • # 2: if letter “K” appears in the circles -> press button
      • If letter K appears in the grey dots -> ignore
    • Here, your attention/spotlight is on 5 dots
    • There’s 2 subjects (A and B)
      
      • Red = activation; blue = inhibition
      • Top L red dot = bottom R area (red)
    • MP: This shows attention can split into 2 spotlights
  • e.g., multiple object tracking
    
    • t1: fixate at centre (x)
    • t2: four yellow blinks
    • t3: dots begin to move
    • t3: which dots where the ones that blinked?
    • Apparently, it’s an easy task
    • We can track all 4 correctly
    • This is inconsistent attention spotlight theory
      
      • If the spotlight theory were true, we would also be tracking the distractors, and our performance would be at chance lv

Question 4

Model of attention

• Biased-competition model of attention (Desimone & Duncan, 1995).
• Competition define
  
  • more competition → v4 neuron activity?
  • effect on v1
• Bias
  
  • bottom-up bias
  • top-down bias
• Kastner et al 1998: fMRI data support competition and bias
  
  • method: 1 at a time vs silmultaneous
  • Results
    
    • meaning of axis
    • meaning of top row
    • Bottom left: area V4
    • Top left
    • Right bottom graphs

Answer 4

Biased-competition model of attention (Desimone & Duncan, 1995).

• Competition: Stimuli in the visual field compete for limited processing capacity & control of behaviour (e.g., overlap in RFs).
  
  • Ex. if there’s too much shit, v4 neurons = weaker activation
• Ex. input to v1 (too much input) -> there’s bottle neck effect due to competition
• x
• Bias: Competition biased towards certain stimuli depending on
  
  • bottom-up bias: salience
    
    • Big vs tiny bunny
    • Ex. Big bunny is more salient than the small ones -> Big bunny is the input
  • top-down bias (e.g., instructions, spatial cues, feature cues).
    
    • Ex. instructed to look at the tiny bunny -> attention (area v4) shrinks to focus on tiny bunny
    • • Kastner et al 1998: fMRI data support competition and bias
  • # 1: fixate at the dot (FP) at lower visual field
  • # 2: present stimuli in upper visual field (for 250 ms)
    • Stimuli has lots of color & textures (v4 neurons love color)
      
      • V4 neurons have receptive fields that are large
  • # 3: present next stimuli (for 250 ms) (and then 2 more patches)
    • IOW: in 1s (250 ms x 4), you see a sequence of 4 patches
• More competition = simultaneous presentation (for 250 ms)
  
  • MP: stimulate the neuron that has receptive field at the circle
  • # 1: all stimuli -> #2,3,4 = empty screens
• Results
  
  • Y-axis = BOLD signal
  • X-axis time
  • Top row: SEQ SIM SIM SEQ = you see the sequential, then simultaneous condition, etc…
    
    • Overall: sequential condition -> break -> simul con -> break -> …
  • Bottom left: area V4 response differ for seq vs sim condition
    
    • Seq condition stronger responses than sim condition
    • This indicates there is competition
    • Competition: stimuli presented SIM compete (in v4) more than SEQ stimuli
  • Top left: in v1 SEQ and SIM = no diff
    
    • Reason: v4 receptive field (orange circle) all 4 patches can fit into the circle
    • V1 (yellow circle) is way tinier, the neuron doesn’t care about the SEQ and SIM -> less competition
• Right bottom graphs
  
  • Attention modulation
  • Trial 1 SEQ, trial 1 SIM -> pay attention to the dot (FP)
  • Trial 2 SEQ, trial 2 SIM -> pay attention to the stimuli
  • Top-down bias: attention to one of the stimuli (vs attention to FP) “overcomes” the competition
  • When we pay attention to the stimuli (blue bars), the diff b/w the SEQ and SIM is smaller
  • When we pay attention to the FP, the diff is greater
  • IOW: attention to patches -> overcomes the competition
    *

Question 5

Model of attention

• Premotor theory of attention (Rizzolatti et al., 1986)
  
  • 3 tenets
• Can you shift attention w/o moving your eyes?
• Can you move your eyes w/o shifting attention?
• Support for the premotor theory of attention
• # 1: Deubel and Schneider (1996)
  • method
  • results
  • Control method
  • results
  • implication on oculomotor program
• # 2: Corbetta et al. (1998)
  • attention activates what areas?
  • red = ?
  • green = ?
  • MP?

Answer 5

Premotor theory of attention (Rizzolatti et al., 1986)

• Attention is like eye movements
• (1) Strict link between orienting of attention (covert attention) and programming explicit ocular movements (overt attention).
• (2) Attention is oriented to a given point when the oculomotor program (get you ready to move eyes) for moving the eyes to that point is ready to be executed.
• (3) Covert orienting of attention (w/o eye movements) is achieved by inhibiting the execution of the eye movement itself.
  
  • Can you shift attention w/o moving your eyes? SURE!
  • Can you move your eyes w/o shifting attention? NO!
• X
• Support for the premotor theory of attention
• # 1: Deubel and Schneider (1996)
  • Attention and eye movements are closely coupled
    
    • 1: look at FP , If it is green -> focus on green circle
    • # 2: Digits briefly presented before saccade
    • # 3: When you are planning to do a saccade, the numbers change (ex. 8-> 3)
    • Results: Digit at saccade target is better perceived (1 = red, 2 = green, 3 = blue)
      
      • # 2 = target; all ppl do better w/ the target
      • # 1 = red circle, is closer to the fovea, should be easier to see; but performance is worse
    • Control: see FP (green) -> need to pay attention to green and red areas as well
      
      • Same results
      • IOW: you cannot shift your attention when your oculomotor program is directing you to the green area
• # 2: Corbetta et al. (1998)
  • Shifting attention and eye movements employs largely overlapping frontoparietal networks
  • These areas are active (no need to worry this the terms for the exam)
    
    • TOS: transversal occipital sulcus
    • pIPS: posterior intraparietal sulcus
    • aIPS: anterior …
    • STS: superior temporal sulcus
    • PrCes: precentral sulcus
    • FO: frontal operculum
  • Flat version of the brain, showing voxels
    
    • Red = covert (just shift your attention)
    • Green = overt (eye movements)
    • Yellow = activated by overt and covert shift
    • -> many yellow areas/ overlap
  • Shifting attention -> slightly more activation
  • But similar activation patterns b/w shifting attention and eye movements

Question 6

Networks of attentional control

• fMRI studies tend to use endogenous cues → why?
• Grent-’t-Jong & Woldorff (2007).
  
  • methods
  • 1st trial: 3 steps
  • control condition
  • fMRI results
    
    • LHS?
    • Centre?
    • RHS?
    • Red circle?
    • blue circle?
  • Cons of fMRI
  • fMRI + ERP help us do what?
  • ERP
    
    • red?
    • blue?
    • Result?

Answer 6

Networks of attentional control

• fMRI studies tend to use endogenous cues
  
  • fMRI are slow machines
  • if we use exogenous cues (may have inhibition of return – least lec)
• (Endogenous) attentional cueing involves a parieto-frontal network.
  
  • Grent-’t-Jong & Woldorff (2007).
    
    • Used fMRI + ERP.
    • Used Cue to shift spatial attention
      
      • (‘L’ or ‘R’); L = left; vv
  • 1^st trial: there’s FP, L and R boxes = where cue may show up
    
    • # 1: Near the FP, there’s “L”, indicating you should shift your attention to the L box
    • # 2: Faint target shows up
    • # 3: indicate if you saw the target
• Control condition: Cue NOT to shift attention = control condition (‘P’)
• => sort out visual & memory components of cue processing
• fMRI
  
  • LHS = shift condition
  • Centre = control condition
  • RHS = +ve responses (only activation for shift)
  • Shift – “no shit” = only the regions activated in shift
• Red circle = frontal eye fields
• Blue circle = parietal eye fields
• Why do we need “frontal” and “parietal”?
  
  • fMRI can’t tell you which pattern showed up first
  • ERP can tell the time sequence
  • But we can use fMRI data to identify sources of ERP signal:
• EEG:
  
  • red = frontal eye field, activate at 400 ms
  • Blue = parietal eye field, activate at 600 ms
• Frontal eye fields activated before Parietal eye fields
• This suggest the frontal eye field may cause attention activation

Question 7

Networks of attentional control

• What Tirin Moore did with the FEF.
  
  • location of electrodes
  • Purpose
  • Methods: 2 steps
• FEF and eye movements → ?
• Subthreshold microstimulation in FEF →?
• Implication

Answer 7

• What Tirin Moore did with the FEF.
• Placed 1 electrode at frontal eye field, another at corresponding (same side) v4
  
  • Based on the v4 recording, we can determine what are of the visual field the v4 neuron like
  • • # 1: have monkey look at FP
• # 2: present stimuli across the visual field (yellow)
• Ex. here, the stimuli at the green location -> v4 activates = receptive field of area v4
• X
• FEF controls eye movements
  
  • When we send small current to the FEF, we can create eye movements in specific directions and sizes -> direct attention
  • Ex. send current -> cause monkey to shift eye movement to the black circle (movement field), which overlaps w/ the green circle (target)
• IOW: Overlap of receptive fields in V4 & movement fields in FEF
• Part 2:
  
  • Reduce stimulation in FEF -> monkey will keep fixaing at the FP
    
    • Only provided Subthreshold microstimulation in FEF (very little current) -> doesn’t cause shift of eye movement, but still cause shift of attention
  • Subthreshold microstimulation in FEF (won’t cause eye movements) -> monkeys shift attention -> attention-like effects in V4 (corresponding v4 site)
  • Thus FEF is the central hub for attention

Question 8

Networks of attentional control

• Corbetta & Shulman’s DAN and VAN
  
  • Dorsal Attentional Network → type of attention?
  • Ventral Attentional Network → type of attention?
  • Exogenous attention activates which networks ?
• Lesion studies → result?

Answer 8

Corbetta & Shulman’s DAN and VAN.

• Dorsal Attentional Network** for goal-directed (**endogenous**) selection and responses + **exogenous attention. Associated with both hemispheres.
  
  • Blue -> there’s activation in FEF and parietal areas, located more DORSAL
• Ventral Attentional Network for unexpected, salient stimuli, circuit breaker (ex focus on 1 task -> distraction -> break circuirt of attention). Mainly associated with the right hemisphere** (**only exogenous attention).
  
  • IOW: exogenous attention activates BOTH DAN and VAN (blue + yellow)
• Based on fMRI studies
• Limitation of fMRI: correlative studies.
• To establish causality -> cut out areas
  
  • Look at ppl w/ have lesions in those areas
  • If we superimpose lesions of these patients -> damage in parietal/frontal region
  • This overalps w/ the R VAN and DAN
  • Lesions in the LH does not cause spatial neglect

Question 9

Disorders of attention

• spatial neglect
• Contralesional
• Co-morbidities → 2
• When comparing lesion sites and VAN DAN activation maps
  
  • → which areas overlap?
• Neglect patients & writing/drawing/makeup/shaving
  
  • Line bisection task
• x
• Bisiach & Luzzatti (1978): The Milan Cathedral experiment.
  
  • methods
  • results
  • What is affected in neglect patient
• x
• Is Neglect relative to the body or relative to objects?
• Niemeier & Karnath, 2002
  
  • Methods
    
    • 2 tasks
  • Results:
    
    • top strand
    • bottom strand
    • top vs bottom strand
• Caloric stimulation: what happens?
• Perenin (1997) - French patient & mapping
  
  • method
  • neglect symptoms in results
  • Implication

Neglect: VAN or DAN?

• When you have a lesion in DAN in the RH -> ?
• Patients do a visual space task (ex. search letter in the sphere)
  
  • Voluntary search task = ?
    
    • Results
    • Yellow = ?
    • Arrows
  • Stimulus driven search task = ?
    
    • method
  • Results
    
    • Voluntary saccades
    • Stimulus-driven saccades
    • Implication

Answer 9

• Spatial neglect
• X
• Spatial neglect: an inability to attend to or respond to stimuli in the contralesional visual field, typically after right brain damage
  
  • Contralesional: brain damage to LH -> affect R visual field
• Co-morbidities very common:
  
  • Visual field defect: a portion of the visual field with no vision or with abnormal vision, typically resulting from damage to the visual nervous system
    
    • Homo/quadroxxopia
  • Motor deficits: paralyzed arm etc.
• “Pure” spatial neglect possible (no comorbids)
• X
• Typical lesion sites:
  
  • inferior parietal cortex (angular gyrus)
  • temporo-parietal junction
  • superior temporal gyrus
  • ventral prefrontal cortex and insula
  • basal ganglia, thalamus
• Based on the VAN DAN activation map
  
  • There’s overlap: VFC, TPJ (NOT STG)
• X
• Neglect patients have trouble with writing and drawing
  
  • Ex. only fill in the right visual field; ignore the LS
• May shave only one side of the face, or dress only the right side of their body
• Line bisection??? (last lec: shown line, indicate the mid point)
  
  • Only SOME patients make a bisection biased to RS
• X
• Many patients w/ visual neglect ignore the space in their minds
• Visual imagery impaired
• Bisiach & Luzzatti (1978): The Milan Cathedral experiment.
  
  • # 1: imagine you are standing at the open area in Milan cathedral, name the buildings on the LS and RS
  • -> patients only list the buildings on the RS, not LS
  • # 2: imagine you walk up to the stairs of the cathedral and turn around; describe the buildings on the LS and RS
  • -> patients only list the buildings on the RS, not LS (even though the building existed in the prev vantage pt)
  • IOW: spatial cog processes are affected in neglect
• Is Neglect relative to the body or relative to objects?
• Niemeier & Karnath, 2002
  
  • Probably both, depending on task
  • # 1: patients in a sphere, have random letters in it
    • They were told to locate the letter A
    • OR locate ORANGE letter As (orange is located in a specific area at the RS)
  • Aerial view
    
    • Patient w/ RH damage
    • Horizontal strands = Flattened sphere
    • Top condition: Where is the A?
      
      • White lines: patients only searching in the orange, green, grey fields on the RS; totally ignoring the LS
      • IOW: the LS relative to the body is completely ignored
    • Bottom: Where is the orange A?
      
      • White lines are only on the R part of the orange region
    • Comparing top and bottom:
      
      • Top image -> attention is on LS and RS of the orange area
      • Bottom image -> attention is only on the RS in the orange area
    • This suggests that eye movements prefer the right side of the sphere or of the orange segment, depending on the task.
• Neglect symptoms can be significantly reduced with caloric stimulation (other senses)
  
  • Caloric stimulation: shoot cold water into the ear
    
    • When you shoot cold water in the ear, it stimulates your sense of balance -> spinning sense
    • • Perenin (1997)
  • A patient in France who was good w/ geography
  • Told to imagine a map of France
  • Name the villages
  • Circles = the towns the patient mentioned
  • When there’s no caloric stimulation -> the neglect the villages in the LS of France
  • Used caloric stimulation (shoot cold water in the L ear) -> same task
    
    • She could name the villages on LS and RS
  • This shows an interaction b/w senses: balance w/ vision

Neglect: VAN or DAN?

• When you have a lesion in DAN in the RH -> deactivates the VAN in RH
• Patients do a visual space task (ex. search letter in the sphere)
• # 1: Voluntary search task -> own eye movements
  • Neglect patients search only the right side but voluntary saccades are the same in both directions.
    
    • Yellow = patients only look at the RS
    • But the arrow directions go both ways
• # 2: Stimulus driven search task
  • Red boxes are flashed, patients need to shift their eyes to the red box and determine if the letter “A” is there
• Results
  
  • Voluntary saccades: eye movements to L and R are perfectly fine
  • Stimulus-driven saccades in leftward direction are impaired.
    
    • Leftward eye movements were smaller sized and more frequent
    • (ex. p -> Z)
  • Neglect could reflect the combined breakdown of VAN and DAN
    
    • IOW: Neglect affects voluntary mechanisms (DAN) and reflexive mechanism (VAN)

Question 10

Disorders of attention

• Extinction - define
  
  • method
  • Results
• Does it apply to other senses?
• Balint’s syndrome → define
  
  • Three cardinal symptoms
  • Humphreys & Riddoch (1992) - dots
    
    • describe the 4 cases
    • What principle is applied iii case 4 to moderate the effect?
• Recall illusory conjunction
• Friedman-Hill et al. (1995):
  
  • procedure w/ Balint syndrome patients
  • Implication
• Loss of global perception
  *

Answer 10

Extinction & Balint Syndrome

• Extinction: Parietal lesions either in left or right brain
  
  • # 1: have patient fixate at your nose
  • # 2: tell them to report it when they see your finger wiggles
• Results:
  
  • When only 1 finger wiggles, they report it correctly (Intact detection of single stimuli)
  • Unable to detect contralesional stimuli when presented together with ipsilesional one.
    
    • IOW: When you wiggle both fingers, they report on 1 finger is wiggling
    • Ex. RH lesion -> ignore wiggling on the L visual field
• This applies to other senses, ex audition, touch
• X
• Balint’s syndrome.
  
  • Bilateral occipito-parietal lesions (severe)
• Three cardinal symptoms:
  
  • Reduced spatial localization: optic ataxia
    
    • Ex. tell the patient to grab your finger on the LS; patients struggles
  • Simultanagnosia: only see 1 thing at a time
    
    • Ex. If you provide a superimposed image (ex. moon and cloud), they say they only see a moon
  • Reduced eye movements: ocular apraxia.
    
    • Glued to 1 object, struggle to move their eyes to somewhere else
• Humphreys & Riddoch (1992)
  
  • Told Balint syndrome patients to report colors
  • Show LS panel (all red) -> patient sees red
  • Shows centre panel (all green) -> patient sees green
  • Shows RS panel (red + green) -> patient ONLY sees red
  • But if you connect the red and green dots (gestalt principle of connectedness)
    
    • -> red + green dots => an object
    • Patients sees red + green
    • IOW: gestalt principles can modulate Balint syndrome’s simultanagnosia
• Illusory conjunctions:
  
  • Last lec –
    
    • # 1: present colored letters briefly
    • # 2: report what you see
      • You can report the colors only OR letters only correctly
      • When asked if you saw a specific combo of letter + color (conjoined) -> incorrect
      • Ex. there’s a blue T -> you say you saw a red T
  • Friedman-Hill et al. (1995):
    
    • # 1: showed Balint patient 2 colored letters for unlimited time
    • # 2: Patient made illusory mistakes 10% of the time
    • Balint’s patient R.M. shows difficulties with binding under free viewing conditions!
    • • This is consistent w/ the search theory (antrisman and laid??)
  • Preattentive stage
  • Attentive stages
    
    • You need spatial attention to conjoin features like color and shape
  • Balint patients have severe spatial attention deficit -> cannot conjoin those features
• Loss of global perception
  
  • When shown hierarchical figures (Ex. an L composed of letter Ks), patients struggle to the L