Attention I
Attention
Wolfe et al Ch 7
Dana said that most vision is agenda-driven. He introduced the slide where the people attended to the many weird
surrounding objects before the test (including the upside-down cow). However, during the test, they only attended
to the purple blocks (when they had an agenda), though there was still some attention given to other objects. Is it
possible to completely ignore the other objects? Also, if the screen were blank until the absolute beginning of the
test and the subject was told to only attend to "the purple blocks," would they be able to consciously ignore the
other objects without first getting a survey of the entire image?
We know that processing stimuli is limited; we simply cannot (or do not) see everything in a scene. However, is this
something that can be trained (and the processing availability increased), in, for example, people that are private
detectives or military jobs, etc.?
Top-down and bottom-up signals of attention control are not totally separated, and my question is where are they
integrated? A paper by Thompson et al. (2005) shows that FEF has a salience map that topologically integrate
those signals as revealed by error signals. Do you know any other regions also have similar or different
mechanisms that integrate bottom-up and top-down signals?
What is attention?
• Arousal: a global state, ‘alertness’
Asleep
Awake
drowsy
alert
hyper
• Attention: selective allocation of resources to certain
stimuli, normally at the expense of other stimuli
Selective attention
Asleep
Awake
drowsy
alert
hyper
What guides attention?
What guides attention?
What guides attention?
Why do we need attention?
• Process behaviorally relevant
stimuli
• Filter out the irrelevant stimuli
• Limited processing resources
• Too much information
Why do we need attention?
• Process behaviorally relevant
stimuli
• Filter out the irrelevant stimuli
• Limited processing resources
• Too much information
What guides attention?
Endogenous (from within)
Exogenous (from outside)
•voluntary
•reflexive
•goal directed
•automatic
•prior knowledge
•naturally salient
•‘top down’
•‘bottom up’
Endogenous cues (Posner paradigm)
Endogenous cues (Posner paradigm)
Faster reaction
times for validly
cued trials →
benefit of attention
being directed to
target location
Another way of thinking about how attention is controlled
Virtual Humanoid has a small library of simple visual behaviors (modules):
– Follow Sidewalk
– Pick Up Blocks
– Avoid Obstacles
Modules use visual routines
to update their state information
Sprague, Ballard, & Robinson TAP (2007)
Each behavior uses a limited, task-relevant selection of visual information from
scene.
Behaviors have different priority/ reward value.
Why do we need attention?
• Too much information
• Limited processing resources
• Process behaviorally relevant
stimuli
• Filter out the irrelevant stimuli
Stroop Effect
What color is the font?
green
blue
yellow
black
brown
pink
What color is the font?
green
blue
yellow
black
brown
pink
The information that is processed is not entirely under the
observer’s control. ie exogenous can trump endogenous in
this case.
But reading a work is clearly not “reflexive”. Need to re-think
this simple classification.
Why do we need attention?
• Too much information
• Limited processing resources
• Process behaviorally relevant
stimuli
• Filter out the irrelevant stimuli
Processing bottlenecks
Attentional Blink (RSVP rapid serial visual presentation)
Target
11 stimuli per
second
What is the likelihood of
detecting a second target
based on its distance from
the first?
Processing bottlenecks
Attentional Blink (RSVP)
First
Target
Second
11 stimuli per
second
Processing of first target
interferes with the ability to
process the second
Is “limited processing resources” the right way to think about it?
Fundamental sequential nature of processing perhaps results
from the sequential nature of actions.
When does attention exert its influence?
• Early selection - low level gating mechanism that
filters (or attenuates) irrelevant information before
completion of perceptual analyses
Broadbent model - gating early based on fundamental
physical characteristics (e.g., color, frequency, location)
determining what needs to be processed
Auditory selective attention
Dichotic listening
At what stage of
stimulus processing
does attention come
into play?
ERPs a good index
shadowing
When does attention exert its influence?
• Early selection - low level gating mechanism that
filters (or attenuates) irrelevant information before
completion of perceptual analyses
Triesman model - adaptive filter that attenuates
irrelevant information in a flexible manner (some
unattended information would make it through)
When does attention exert its influence?
• Late selection - all stimuli are processed through
completion before attentional selection occurs
Hybrid model - filtering at various processing levels
depending on the needs for the task where perceptual
load influences how much is filtered
Attention and the brain
• Dynamic interaction between attentional control
network and stimulus processing regions
• Attention modifies the way you perceive the world and
your behavior
2
1
Auditory ERPs to a tone
Early brainstem (10 ms):
Auditory brainstem nuclei
Early cortical (10-50 ms):
Primary auditory cortex
Late cortical (>100 ms):
Auditory association areas
Compare ERPs
for attended vs.
unattended ear at
these different
stages
Early vs. late selection in audition
* Deviant tone
Early vs. late selection in audition
* Deviant tone
Between Ears → Early Selection
Early vs. late selection in audition
* Deviant tone
Between Ears → Early Selection
Within Attended → Late Selection
Early vs. late selection in audition
No
brainstem
Early vs. late selection in audition
Early
cortical
Effects on stimulus processing
• Enhancing the gain
(increasing activity)?
• Extending the duration
of the processing?
• Narrowing the tuning
curves of relevant
neurons?
1
Effect on V4 neurons
Reduced activity
even though an
effective stimulus in
receptive field
Effect on V4 neurons
Tuning curve
unaffected
Spike rate
increased → affect
on gain
Attentional effects on features
Attend to moving or attend to stationary
Attention to motion enhances MT+ signal
Summary
• Attention is the selective allocation of resources to certain
stimuli and the ability to filter out distracting ones
•
Endogenous and exogenous factors influence attention
•
Attention modulates the activity of multiple brain regions
(evidence for early and late effects)
•
Attention mainly affects the gain (the amplitude) of
sensory regions (??)