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11 Attention

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Introduction

I. Attention: State of selectively processing simultaneous sources of information

II. Benefits: Performance of behavioral tasksIII. Brain Imaging – changes in cortical activityIV. Behavioral manifestations

Visual attention; Auditory attention

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Introduction

Functions of attentionA. Concentrate on one object in visual fieldB. Selectively attend to information (while

ignoring other information) C. Preferential processing of sensory

information Attention-deficit hyperactivity disorder

Demonstrates critical nature of intact attentional mechanisms

Brain imaging studies Show that cortical activity is altered by

attention

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Behavioral Attention

Visual attentionA. Move eyes until object imaged on foveaB. Shifting attentionC. Enhanced visual processing

1) Enhanced detection2) Faster reaction times

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Behavioral Attention

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->

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Behavioral Attention

Faster Reaction Times

Enhanced Detection

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Behavioral Attention

Neglect Syndrome as an Attentional DisorderPerson ignores objects, people, and their own

body to one side of the center of the gaze

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Physiological Attention

Shifting attentionA. What happens to neural activity?B. What brain areas are involved?

Observed in high-level cognitive and numerous sensory arease.g., Area V1 to visual cortical areas in the parietal and temporal lobes

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Physiological Attention

I. Functional MRI Imaging of Attention to Location

A. Subjects view stimulus

B. Change location of attended sector

C. Brain activity shifts retinotopically

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Physiological Attention

PET Imaging of Attention to Features

A. Same-different discrimination task

1. Features: Color, shape, speed

2. (A) Selective attention: one feature

3. (B) Divided attention: all features

4. Subtract B from A shows brain activity associated with attention to one feature

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Physiological Attention

PET Imaging Attention to Features

Speed

Color

Shape

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Physiological Attention

Enhanced Neuronal Responses in Parietal CortexA. Attention: Experimental vs. Normal

conditionsB. What happens to attention under normal

conditions?C. Test the Hypothesis:

Attention changes location prior to eye movement

D. Wurtz, Goldberg, and Robinson: Record neural activity from Posterior Parietal

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Physiological Attention

Enhanced NeuronalResponses in Parietal Cortex A Posterior parietal cortex

neuronsB Directing eye

movementsC Response significantly

enhanced neuronal response when eyes went to target

Its either an attention shift or a premotor signal

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Physiological Attention

Receptive Field Changes in Area V4

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How is Attention Directed?

I. Cortical, subcortical areasA. Modulate the activity of neurons in sensory cortex

areasII. The Pulvinar Nucleus

A. In humans: Damage to the PN results in slow responses to stimuli on the contralateral side

B. Muscimol (GABA agonist;suppresses activity) inmonkey PN results in impairment of attention shifting

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How is Attention Directed?

I. Attention and Eye MovementsA. Eye moves to attended objectB. Eye movements & attention closely

relatedC. Recent experiments

1. Brain circuitry: Directing eyes to objects of interest

D. Frontal Eye Fields (FEF)1. Cortical area2. FEF neurons

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How is Attention Directed? Attention and Eye Movements (Cont’d)

Experiment1. Train monkeys to look at

display of small light spots2. Place electrode in FEF and

determine motor field of neurons at the tip

3. Small electrical stimulation enhancement?

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How is Attention Directed?

Attention and Eye Movements (Cont’d)Results

FEF involved in directing attention; Enhancing visual performance

ConclusionGuidance of attention

Integrated with system to move eyes

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Concluding Remarks

I. Studies of attentionA. Point to flexibility of the human brain

II. More mental energy to one locationA. Enhanced sensitivity & reaction timeB. Ignoring competing stimuli

III. Need for attentionA. e.g.,- Cannot process ALL information in

area V1B. Selects what information should access

the limited processing resources

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End of Presentation