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 attentionAsleep 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)
•voluntary
•goal directed
•prior knowledge
•‘top down’
Exogenous (from outside)
•reflexive
•automatic
•naturally salient
•‘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
Virtual Humanoid has a small library of simple visual behaviors (modules):– Follow Sidewalk – Pick Up Blocks– Avoid Obstacles
Each behavior uses a limited, task-relevant selection of visual information from scene.Behaviors have different priority/ reward value.
Sprague, Ballard, & Robinson TAP (2007)
Another way of thinking about how attention is controlled
Modules use visual routinesto update their state information
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?
greenblue
yellowblackbrownpink
What color is the font?
The information that is processed is not entirely under the observer’s control. ie exogenous can trump endogenous inthis case.
But reading a work is clearly not “reflexive”. Need to re-thinkthis simple classification.
Why do we need attention?
• Too much information
• Limited processing resources
• Process behaviorally relevant stimuli
• Filter out the irrelevant stimuli
Processing bottlenecks
Target
Attentional Blink (RSVP rapid serial visual presentation)
11 stimuli per second
What is the likelihood of detecting a second target based on its distance from the first?
Processing bottlenecksAttentional Blink (RSVP)
Target
11 stimuli per second
First
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 resultsfrom 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 attentionDichotic 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
1
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
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 brainste
m
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 (??)
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