Attention A classic definition: Everyone knows what attention is. It is the taking possession by the mind, in clear and vivid form, of one out of what

Attention

• A classic definition:Everyone knows what attention is. It is the taking possession by

the mind, in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of thought. Focalization, concentration of consciousness are of its essence. It implies withdrawal from some things in order to deal effectively with others…

William James

James’ Attention• “Taking possession of the mind…”

– Attention has a voluntary aspect

• “…of one out of what seem several simultaneous possible objects or trains of thought…”– Attentional capacity is limited– Attention involves a process of selection– Attention is not only focusing but also ignoring

• “…withdrawal from some things in order to deal effectively with others…”– Ignoring is an active process

Early Research Demonstrating Limited Capacity

• E.C. Cherry (1953)• Selective auditory

attention• “Dichotic listening”

procedure• Subjects given different

inputs to each ear• Subject asked to report

input from one ear first then other ear second

• Subjects unable to report unattended channel

Early Research Demonstrating Selection and Inhibition:The Cocktail Party Effect

• A relevant conversation can be attended to in spite of a welter of background conversation…

• But attention can be captured by some meaningful stimulus event occurs in that background

What is attention??

• Traditional information processing views: Based on limits to simultaneous processing.

• Mechanisms exist to filter, gate, select or inhibit.

• Prevailing view for years: Broadbent Bottleneck

• A basic conversion from massive parallel input to a limited or serial processing mode.

The brain and attention

• Processing models (stone ages)• Biological theories

Cortex!!• Parietal• Frontal

Neurochemistry!!• Ach• NA• DA





Broadbent’s Filter Theory of Attention

• An “early selection” model (1958)

The Early Selection Model fell, due to its inability to account for many experimental results.

The answer to this: “Late Selection”

• All stimuli processed to a “semantic” level, then selected on the basis of task relevance

Problem with Information Processing View: It doesn’t account for the brain.

Sequel to information processing:

• Hi degree of parallel processing

• Flexible allocation of resources

• Attention interacts with motor output.



Cortex!!• Parietal (neglect)• Frontal




Cortex!!• Parietal (neglect, cued orienting, biased competition)

• Frontal

Neurochemistry!!• Ach

• NA

• DA

Early Research in the field of perception had already addressed a more “modern view”

• Hermann von Helmholtz• Electric spark randomly

illuminated part of the screen

• Centrally-fixed gaze• Moved attention to a part

of the screen• Found he could discern

letters in the illuminated part if his attention was fixed there PRIOR to the spark

Discovered “covert attention”

Along came Posner and Boies

• Attention is not a unitary phenomenon.

• Alertness or Readiness to take in information (concentration, vigilence)

• Selective Attention – search a display or an environment for a particular target.

Selective Attention Was Divided a Fluid Process With Three Components

• Engage

• Disengage

• Move– A Visuospatial Attention Task Was devised to

test this hypothesis and begin to map attention on to “visual” areas of the brain.

The Typical Result is:A “benefit” of valid cuing (faster reaction times and more accurate responding) and a “cost” of invalid cuing (slower reaction times and less accurate responding).

ENGAGE

MOVE

DISENGAGE

An early mapping of visuospatial attention by Posner

Classic Effect of Right Posterior Parietal Cortex Damage on Covert Orienting Task




Neurochemistry!!• ACh• NA• DA

Basal Forebrain Projections

Voytko

Selective lesions of the cholinergic neurons in the basalforebrain of rats produces the same increased cost – What does this say for Posner’s Theory???



Cortex!!• Parietal (neglect, cued orienting, biased competition)

• Frontal

Neurochemistry!!• Ach

• NA

• DA

James’ Attention• “Taking possession of the mind…”

– Attention has a voluntary aspect

• “…of one out of what seem several simultaneous possible objects or trains of thought…”– Attentional capacity is limited– Attention involves a process of selection– Attention is not only focusing but also ignoring

• “…withdrawal from some things in order to deal effectively with others…”– Ignoring is an active process





Classic Task Examining Inhibition of Classic Task Examining Inhibition of attention: Negative priming (Tipper) taskattention: Negative priming (Tipper) task

• One picture is superimposed upon another.– One is printed in red the other in green ink.– Participants are told to name one (always red

ink) and to ignore the other (green ink).– Before each trial a prime is presented briefly.– Naming a red trumpet is affected when the

prime is a red kite and a green trumpet (ignored) compared to when the prime is a red kite and a red anchor.

– Ignored information must be actively suppressed.

• The Stroop effect in psychology is a demonstration of interference. When color words such as blue, green, red, etc. are printed in various colors and someone is asked to say the color the words are printed in rather than reading the words, it is very difficult to do, at least at first. The effect is named after its discover, John Ridley Stroop, who wrote an article on it in 1935.

Stroop effect- another classic Test of Attentional Inhibition OR Impaired

Response Inhibition

Green

Yellow

Red

Purple

Blue

Red

Black

Yellow

Orange

Blue

Purple

Red

Green

Black

Blue

Yellow

Green

Red

Purple

Blue

Blue

Brown

Blue

Red

Green

Green

Yellow

Red

Yellow

Orange

Blue

Red

Green

Yellow

Black

Yellow

Orange

Red

Purple

Blue

Purple

Red

Green

Black

Blue

Yellow

Green

Red

Purple

Blue

Green

Yellow

Red

Yellow

Orange

Blue

Brown

Blue

Red

Green

Who has trouble with Negative Priming and Stroop??

• Patients with Frontal Lobe Damage

• Patients with Frontal Dementia

• Children

• Chronically Stressed Patients





A principled model of attention?

“ we have shown that the orientation of attention - specifically, the disengagement or movement of attention- is mediated by acetylcholine”

(Phillips et al, 2000)

Schultz, Dayan & Montague 1997

Expected Reward

v = wu

v : expected reward w : weight (association) u : stimulus (binary)

Rescorla-Wagner Rule

Association update rule: w w + αδuw : weight (association)

α : learning rateu : stimulus

Prediction error: δ = r - vr : actual reward

v : expected reward

Uncertainty (σi²)

Kakade, Montague & Dayan, 2001

The cholinergic basal forebrain

A role of uncertainty in attention?

Is this uncertainty mediatedby acetylcholine?

Kalman weight update rule:

wi wi + αiδ

With associability:

α i = i² ui

jj² uj +E

wi wi + αiδ

dopamine?acetylcholine?

α i = i² ui

jj² uj +E

Documents

Attention A classic definition: Everyone knows what attention is. It is the taking possession by the mind, in clear and vivid form, of one out of what