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 (??)