Participants

Right-handed, community-dwelling individuals; 16 younger adults (19-28 years; 8 female); 16 older adults (60-82 years; 8 female). Participants were screened for major health problems and use of psychotropic medication.

Imaging Parameters

Structural: T1-weighted near-axial gradient-echo images, 21 contiguous slices, parallel to AC-PC, 5 mm thick; TR = 450 ms; TE = 3.5 ms.

Functional: T2* Spiral-out gradient echo, co-registered to T1s, TR = 1500 ms, TE = 40 ms, flip angle = 90o; in-plane resolution = 3.75 mm2. Six functional runs.

Regions of Interest (ROIs):

INTRODUCTION

David J. Madden1,2, Julia Spaniol1,2, Wythe L. Whiting6, Barbara Bucur1, James M. Provenzale3, Roberto Cabeza5, and Scott A. Huettel1,2,4

1Center for the Study of Aging and Human Development, Departments of 2Psychiatry, 3Radiology, and the 4Brain Imaging and Analysis Center, Duke University Medical Center; 5Center for Cognitive Neuroscience, Duke University; and 6Department of Psychology, Washington and Lee University

METHOD and RESULTS

CONCLUSIONS

Correlation Between Activation Magnitude and Search Performance (Target Type Effect)

Across task conditions, age-related increases in activation occurred primarily in frontal and parietal regions.

Top-down attention led to increased event-related activation in parietal regions.

In the Guided condition, on singleton target trials, event-related activation was correlated with search performance (the target type effect), and this correlation varied as a function of age group. The activation-performance relation involved the frontoparietal network for older adults and the fusiform gyrus for younger adults.

Adult Age Differences and Similarities in the Functional Neuroanatomy of Visual Attention: Evidence From fMRI

Supported by NIA grants R37 AG02163 and R01 AG11622

TASK CONDITION MEANS

Error rate < 2.0% for each age group.

Reaction time: Age x Condition x Target Type significant, p < .0001.

Separate Trial Blocks Guided Condition: Singleton = target on 75% of trials Baseline Condition: Singleton = target on 25% of trials

Response 1

E

Response 2

REH

K X

EH

K X

EH

K X

Display: 1,000 ms (Younger Adults)

1,500 ms (Older Adults)

Mask: 1,000 ms (Younger Adults)

500 ms (Older Adults)

#

#

##

# #R

N

PK

RN

PK

RN

PK

Superior Parietal Lobule

Target Type Effect (Percentage Difference in Response Time)

r = .52

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.10

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.30

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.50

.60

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.80

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urve

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Frontal Eye Field Fusiform Gyrus

0 4 8 12 16 20 24 28 32 36 0 4 8 12 16 20 24 28 32 0 4 8 12 16 20 24 28 3236 36

r = .57 r = .66

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Frontal Eye Field Fusiform Gyrus Superior Parietal Lobule

Target Type Effect (Percentage Difference in Response Time)0 4 8 12 16 20 24 28 32 36 0 4 8 12 16 20 24 28 32 0 4 8 12 16 20 24 28 3236 36

Mixed Blocked/Event-Related Design

Reaction Time Results

Activation Magnitude

Visual Search Task

TARGET TYPE EFFECT

Percentage target type effect (nonsingleton RT – singleton RT)/nonsingleton RT In Guided Condition, older > younger, p < .01.In Neutral Condition, younger = older.

Time(seconds)

Search task trials Search task trials

Fixation

One Task-Fixation Sequence

Six Task-Fixation Sequences per Scanner Run

= Nonsingleton= Singleton

Time (seconds)

Fixation

++

0

5

10

15

20

25

30

Neutral Guided

Tar

get

Typ

e E

ffec

t (%

)

Younger Adults

Older Adults

Rea

ctio

n T

ime

(ms)

400

500

600

700

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900

1000

1100

Singleton Nonsingleton Singleton Nonsingleton400

500

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Singleton Target

NonsingletonTarget

Neutral Condition

Singleton Target

NonsingletonTarget

Guided Condition

Younger Adults

Older Adults

FRONTALRAC = rostral anterior cingulate CAC = caudal anterior cingulateMFG = middle frontal gyrus FEF = frontal eye field

DEEP GRAY MATTERCAU = caudate PUT = putamen THA = thalamus OCCIPITALFFG = fusiform gyrus LOG = lateral occipital gyrus CUN = cuneus

PARIETAL ANG = angular gyrus SMG = supramarginal gyrusSPL = superior parietal lobule

Age-related changes in the functioning of a frontoparietal attentional network have been reported previously, using tasks that combine top-down and bottom-up attentional components. We used functional magnetic resonance imaging (fMRI) to test the hypothesis that normal aging alters this frontoparietal network through changes in the use of top-down attention. To isolate top-down attentional effects, we compared blocks of visual search trials in which the probability of a target-defining feature (color) was either relatively low (neutral condition) or relatively high (guided condition). We hypothesized that the specific form of the difference between the age groups would be an increased magnitude of activation for older adults in the frontoparietal network, especially frontal regions. In addition, we predicted that this activation would be more highly correlated with search performance for older adults than for younger adults.

]

]

]

Sustained Effects: Initial Component Sustained Effects: Steady-State Component

Sustained Effects: Age Group

Transient Effects: Age Group Transient Effects: Task Condition

Frontal Parietal Parietal

Younger Older

Younger Older Neutral Guided

Are

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DR

(x

100

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ANG SMG SPL

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]

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DR

(x

100

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RAC CAC FEF MFG

]

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ANG SMG SPLAre

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DR

(x

100

)

RAC CAC FEF MFG .00

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HD

R

Frontal

]

] Parietal

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ANG SMG SPL

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HD

R

] ]

]

Are

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R

RAC CAC FEF MFG .00

.02

.04

.06

.08 Frontal

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]

] ]

]

]

Parietal

ANG SMG SPL .00

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Reliance on top-down guidance of attention during search is more pronounced for older adults than for younger adults.

Both sustained and transient activation of frontoparietal network is greater for older adults than for younger adults.

The correlation between activation and performance is a top-down effect limited to the Guided condition. The age-related increase in the activation of the frontoparietal network may be a compensatory mechanism responding to decreased efficiency of visual cortical regions.

Younger Adults Older Adults