Participants

1. Six Task-Fixation Sequences per Scanner Run One Task-Fixation Sequence H E Search task trials Search task trials Time (seconds) K X + + Fixation Fixation Younger Younger Older Older R N = Singleton = Nonsingleton K Time (seconds) P Mask: 1,000 ms (Younger Adults) 500 ms (Older Adults) R E Display: 1,000 ms (Younger Adults) H H E E Response 2 Response 1 # 1,500 ms (Older Adults) # # K K X X R R Neutral Guided # N N # # K K P P Separate Trial Blocks Guided Condition: Singleton = target on 75% of trials Baseline Condition: Singleton = target on 25% of trials Older Adults Older Adults Younger Adults Younger Adults 1100 1100 Guided Condition Neutral Condition 30 1000 1000 25 900 900 Frontal Eye Field Fusiform Gyrus Superior Parietal Lobule Frontal Eye Field Fusiform Gyrus Superior Parietal Lobule 20 800 800 r = .52 .80 r = .66 r = .57 .80 Reaction Time (ms) .70 .70 .60 .60 Target Type Effect (%) 15 700 700 .50 .50 Area Under HDR Curve (x 100) Area Under HDR Curve (x 100) .40 .40 600 600 .30 .30 10 .20 .20 .10 .10 500 500 .00 .00 5 0 4 8 12 16 20 24 28 32 36 0 4 8 12 16 20 24 28 32 36 0 4 8 12 16 20 24 28 32 36 0 4 8 12 16 20 24 28 32 36 0 4 8 12 16 20 24 28 32 36 0 4 8 12 16 20 24 28 32 36 Target Type Effect (Percentage Difference in Response Time) Target Type Effect (Percentage Difference in Response Time) 400 400 Singleton Singleton Nonsingleton Nonsingleton Singleton Singleton Nonsingleton Nonsingleton 0 Target Target Target Target Neutral Guided Adult Age Differences and Similarities in the Functional Neuroanatomy of Visual Attention: Evidence From fMRI 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 INTRODUCTION Mixed Blocked/Event-Related Design Activation Magnitude • 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. 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: Age Group Sustained Effects: Initial Component Sustained Effects: Steady-State Component ] ] .05 .05 Parietal Frontal Parietal Frontal .08 Area Under HDR .08 Area Under HDR Area Under HDR Area Under HDR .04 Visual Search Task .04 ] .06 .06 ] .03 ] .03 ] ] ] .04 .04 ] ] ] .02 .02 .02 .02 .01 .01 .00 .00 .00 .00 ANG SMG SPL RAC CAC FEF MFG METHOD and RESULTS ANG SMG SPL RAC CAC FEF MFG Transient Effects: Task Condition Transient Effects: Age Group • 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): Area Under HDR (x 100) Frontal Parietal Parietal Area Under HDR (x 100) Area Under HDR (x 100) .60 .60 .60 ] ] ] ] ] .40 .40 .40 ] ] .20 .20 .20 Reaction Time Results .00 .00 .00 ANG SMG SPL ANG SMG SPL RAC CAC FEF MFG 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. TASK CONDITION MEANS Error rate < 2.0% for each age group. Reaction time: Age x Condition x Target Type significant, p < .0001. Correlation Between Activation Magnitude and Search Performance (Target Type Effect) • 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. Older Adults Younger Adults FRONTAL RAC = rostral anterior cingulate CAC = caudal anterior cingulate MFG = middle frontal gyrus FEF = frontal eye field DEEP GRAY MATTER CAU = caudate PUT = putamen THA = thalamus OCCIPITAL FFG = fusiform gyrus LOG = lateral occipital gyrus CUN = cuneus PARIETAL ANG = angular gyrus SMG = supramarginal gyrus SPL = superior parietal lobule CONCLUSIONS • 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. • Reliance on top-down guidance of attention during search is more pronounced for older adults than for younger adults. Supported by NIA grants R37 AG02163 and R01 AG11622