Attention, perception, and performancedavid/courses/perceptionAdvanced...on nput e perception...
Transcript of Attention, perception, and performancedavid/courses/perceptionAdvanced...on nput e perception...
attention
sensory input
respo
nse
perception
Attention, perception, and performance
• Attention: what is it good for?• Fronto-parietal lesions and hemifield neglect.• Behavioral measures of attention.• Neural correlates of attention.• Computational model of attention• Linking physiology and behavior.
Outline
Attention: what is it good for?
Limited resource- Energy metabolism in the brain can support only ~0.1 spikes/sec/neuron on average.- Perform only one action (eye movement, arm movement, etc.) at a time.
Makes downstream processing easier:- Ignore irrelevant neuronal signals.- Boost reliability of the relevant signals.
Working memory/awareness
Fronto-parietal lobe lesions
Symptoms: neglect extinction denial spatial orientation deficit
Cortical areas damaged
Neglect
Model Patient copy
Line bisection(patient: Frederico Fellini)
Patient PP
I knew the word “neglect” was a sort of medical term for whatever was wrong but the word bothered me because you only neglect something that is actually there, don’t you? If it’s not there, how can you neglect it?
I think concentrating is a better word than neglect. It’s definitively concentration. If I’m walking anywhere and there’s something in my way, if I’m concentrating on what I’m doing, I will see it and avoid it. The slightest distraction and I won’t see it.
Neglect
Extinction
Change blindness
Change blindness
• Eye movements• Reaction time vs performance accuracy• Performance vs criterion• Transient vs sustained• Visual search & feature integration theory• Search revisited with signal detection theory
Behavioral measures of attention
Eye movements
Reliability of eye movements
Covert attention
Measuring behavioral improvements with attention:- Reaction time vs accuracy.- Performance improvement vs criterion shift.- Exogenous (transient) vs endogenous (sustained) attention.
Visual search
Feature integration theory
Conjunction search: find vertical rectangle
Set size effect
Rea
ctio
n tim
e (m
s)
Display size
conjunction
single feature
Cueing protocol
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Relevantset size 1
Relevantset size 8
Relevant set size
Cont
rast
incr
emen
t th
resh
old
Target appears at one of the cued locations on half the trials
Signal detection theory
yes no
Decision integration theory
Decision rule: subject monitors all stimulus locations, target present if any response exceeds criterion.
Set size effect: with a large set size, lots of opportunities for false alarm.
Attention is controlled in posterior parietal and prefrontal cortex
- Parietal (LIP) responses depend on behavioral relevance of the stimulus.
- Possible human homolog of monkey LIP.
Neural correlates of attention
Trained to fixate. Small response from parietal lobe neuron when light comes on in periphery.
Trained to fixate until peripheral light comes on, then must move eyes to look at the light. Identical retinal stimulation. Much bigger response (3x).
Trained to move arm instead of eyes. Same result (bigger response), i.e., not an eye movement control signal. Rather more like the neural correlate of attention/salience.
Neural correlates of attention: LIP
Human visual cortical areas
V1
V2
V3
V3A/BV7
IPS1IPS2
V4
LO1LO2
MT
V2V3
V3A/B
V7IPS1
IPS2
V4
MTLO2LO1
IPS1 and IPS2
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0 10 20 30Time (s)
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fMR
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6s
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12s
15s
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0 10 20 30Time (s)
data: mean ± se
model: mean ± sd
delay period
control
Sustained delay-period activity
Neural correlate of sustained attention (or intention)
peripheral target
delay
fixation dimssaccade
returnsaccadecorrective
saccade
A
B
DC
!14 0 +14!11
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+11
Vert
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egre
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Num
ber o
f tria
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total # of trials per session: 96
cont
rol t
rials
Figure 1
FPT
E
target cue ‘go’ correction
time1.5-15s
delay1.5s 1.5s 10.5-15s
return
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10
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Horizontal position (degrees) Delay period (s)3 6 9 12 15
Delayed saccade task
Attentional modulation in visual cortex
optic nerve
LGN
primary visual cortex
Retinogeniculate pathway
opticchiasm
Attention affects responses in visual cortex
- Boosts baseline firing rates in visual cortex.
- Boosts gain of responses in visual cortex.
- Selects one of multiple stimuli.
Attention increases baseline firing rates
cue start of trial
stimulus is presented
Attention increases gain of neural responses
V4
One stimulus within receptive field and the other contralateral.
Selection
Contrast gain & response gain
Reynolds, Pasternak, & Desimone, Neuron, 2000
Williford & Maunsell, J Neurophysiol, 2006
Log Contrast
C
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AttentionalModulation(%)
NormalizedModelResponse
Log Contrast
F
0
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NormalizedModelResponse
Predominantly Response Gain
AttentionalModulation(%)
B
Log Contrast0
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Predominantly Response Gain
NormalizedModelResponse
AttentionalModulation(%)
Log Contrast
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Mixed Attention Effect
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NormalizedModelResponse
AttentionalModulation(%)
Log Contrast
D
Mixed Attention Effect
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NormalizedModelResponse
AttentionalModulation(%)
Predominantly Contrast Gain
Log Contrast
A
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NormalizedModelResponse
AttentionalModulation(%)
Mixed Attention Effect
AttentionField
Stimulus Ignored AttendedAttentionModulation
ReceptiveField
Figure 4
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Attended Preferred
Attended Null
Attention Field
Attentionalmodulation(%)
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FiringRate(Hz)
Attentionalmodulation(%)40
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FiringRate(Hz)
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Stimulus Ignored Attended% AttentionalModulation
ReceptiveField
Figure 4
Log Contrast Log Contrast
Normalization model of attention
Orientationpref
Orientationpref
Attention FieldRF center
RF center
pool overspace andorientation
Orientationpref
RF center
Stimulus
Orientationpref
Stimulus Drive
RF center
Suppressive Drive
XX
Figure 1
Population Response
Receptive fields Normalization
firing rate response÷
Attention
distractors
target
Stimulus
X
XX
X
X
+
Normalization model
Orientationpref
Orientationpref
Attention FieldRF center
RF center
pool overspace andorientation
Orientationpref
RF center
Stimulus
Orientationpref
Stimulus Drive
RF center
Suppressive Drive
XX
Figure 1
Population Response
R(x,θ) = E(x,θ) A(x,θ)S(x,θ) +σ
⎢
⎣⎢
⎥
⎦⎥
E(x,θ) = e(x,θ)∗ I(x, y) = I(ξ,η)e(∫∫ x − ξ, y −η)dξ dη
S(x,θ) = s(x,θ)∗[E(x,θ) A(x,θ)]
Normalization model
Normalization model
Σ( )normalizedresponse
(unnormalized response)2
unnormalized 2responses
+ σ2
=
Surround suppression
CRF
SurroundSurround ck
sk
CRF
Surround
0 < β < 1 surround suppression
Contrast gain vs response gain
Contrast gain change Response gain change
Small stimulus, large attention field
attentional gain affects stimulus drive and suppressive drive equally
γ > 1
r = α cc +σ
r = α γ cγ c +σ
= αc
c +σ / γ
Large stimulus, small attention field
attentional gainγ > 1
0 < β < 1 surround suppression
r = α cc + βc +σ
r = α γ cγ c + βc +σ
For c >> σ r = α 11+ β
For c >> σ r = α γγ + β
Attention protocol
Time(ms)
Neutral InvalidValid
ITI(1050-1550)
Pre-cue(60)
Stimuli(30)
Response cue(100)
ISI (40)
Interval(200)
1/3 each
Manipulating stimulus & attention field size
Large stimulusno spatial uncertainty
Small stimuluswith spatial uncertainty
Psychometric functions
> 9000 trials/observer4 observers
Large stimulussmall attention field
Small stimuluslarge attention field
Contrast (%)
Perf
orm
ance
(d’)
C50 p < .05
d’max p < .05
C50 n.s.
d’max n.s.ValidNeutralInvalid
10 100
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10 100
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Orientationpref
Orientationpref
Attention FieldRF center
RF center
pool overspace andorientation
Orientationpref
RF center
Stimulus
Orientationpref
Stimulus Drive
RF center
Suppressive Drive
XX
Figure 1
Population Response
Attention field sizeAttention field: spatial spread and featural extent of attention gain factors.
Small targets with spatial uncertaintyvs.
No uncertainty (always middle of 5 locations)
Measuring attention field size
De-emphasize stimulus-evoked responses:• Brief (50 ms) stimulus
presentations.• Small stimuli (<1° radius).• Low (10%) contrast.
Distance from the lower vertical meridan (arc deg of visual angle)fM
RI r
espo
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nge
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tens
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fMRI response amplitudeAttention field centerAttention field size
Attention field size no uncertainty(arc deg visual angle)
Atte
ntio
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inty
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ngle
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0 2 4 6 8
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Left hemisphereRight hemisphere
(deg polar angle)0 20 40 60 80 100 120 140 160 180
Sample hemisphere All hemispheres
Attention field size
Microstimulation in FEF improves performance
Microstimulation in FEF boosts gain of V4 responses