Task• 3 conditions

• Participants decided whether two pictures both matched the cue or not.

• Event-related design, 40 trials per condition

• Items were presented in a randomized order, with a jittered ITI (3 - 10.5s)

Functional & Behavioral Age-Related Changes in Phonological & Semantic Processes Under Distracting Conditions

Michele T. Diaz1,2, Micah A. Johnson1, Anthony Pecoraro1, Deborah M. Burke3, and David J. Madden1,2

1Brain Imaging & Analysis Center, Duke University Medical Center, 2Department of Psychiatry & Behavioral Sciences, Duke University Medical Center, 3Department of Linguistics and Cognitive Science, Pomona College

1 IntroductionThe pattern of age-related change within the domain of language is marked by both retention and decline. Indices of semantic processing such as vocabulary and general knowledge are stable until very old age. In contrast, older adults have increased difficulty with phonological processes as indicated by increased slips of the tongue and tip of the tongue phenomenon [1,2]. While these behavioral patterns are established, the neurobiological changes associated with these behaviors are less clear. Previously, we have shown that older adults were slower and had more errors on phonological but not semantic trials, and showed different patterns of activation during phonological but not semantic processes. In the present study, we examined phonological and semantic processes in the presence of task-irrelevant information. One general area of cognition that older adults may have increased difficulty is in ignoring task-irrelevant information. But how this interacts with language processes is unclear. We used fMRI to test the hypotheses that age-related differences occur in 1) the neural mechanisms of semantic versus phonological retrieval and 2) the relation between these neural mechanisms and behavior.

2 Participant Demographics

* = p< .01, data presented are mean (SD)

ACKNOWLEDGEMENTS: This research was supported by the Brain Imaging and Analysis Center and NIA grant AG 034138 to MTD, DJM, and DMB.

4 Results Behavioral Analyses We examined behavioral performance using a diffusion model of RT. By including both accuracy and response time, it distinguishes the decision-related component of overall RT, termed drift rate (v), from the encoding and response-related components, termed non-decision time (Ter) [3].

fMRI NetworksOur primary analysis examined regions that were selectively engaged by the phonological and semantic conditions, respectively, in a group level analysis for younger and older participants combined. Networks were defined as Phonological > Semantic, masked by Phonological > all other conditions and Semantic > Phonological, masked by Semantic > all other conditions.

www.biac.duke.edu www.duke.edu

3 Imaging Parameters and Task fMRI Parameters and Analysis

• 3T GE MR 750 scanner, 8-channel head coil• Functional images: inverse spiral (TR=2s, 38 axial slices, 3.8x3.8x4 mm3)• Preprocessing and analysis with FSL (cluster corrected, GRF theory, p<.001)• Results from higher-level comparisons were masked by lower level comparisons

Younger Older

N 19 19

Age* 25 (4.9) 67.5 (5.4)

Education 16.4 (2.1) 17.2 (2.0)

MMSE 29.2 (1.0) 29.3 (0.8)

Depression (HADS) 1.1 (1.6) 1.5 (1.7)

Vocabulary (WAIS II) 57.6 (5.4) 57.4 (4.9)

Verbal Fluency (total) 72.3 (18.5) 66.4 (16.6)

Digit Symbol RT* 1271.5 (239.2) 1867.5 (369.9)

Stroop RT* 492.4 (88.5) 647.4 (167.6)

Speed RT* 283.1 (35.5) 313.9 (43.9)

Immediate Recall 11.7 (3.0) 10.8 (2.7)

Delayed Recall* 10.9 (3.7) 9.0 (3.3)

5 Summary and Conclusions• Behavioral measures revealed age-related differences in reaction time and drift rate in both tasks.• Older and younger adults differed in fMRI activation in the phonological task.• Both groups showed a main effect of Match in which Non-Match trials elicited greater activation than Match trials in all trials. • There was a significant relationship between behavior and fMRI activity in the semantic but not the phonological task. • Our results suggest that additional task-irrelevant information increased activation for older adults in the phonological task, but that this increased activation was not tightly coupled with improved behavioral performance.

Semantic Regions Hemi # Voxels X Y ZMax Z

YoungerMax Z Older

IFG Left 2,588 -44 38 -18 7.52 7.58

IFG Right 661 54 26 10 6.20 6.65

Orbital-frontal Ctx Right 27 44 34 -16 2.00 1.67

MFG, posterior Left 833 -40 16 50 5.32 5.42

SFG, posterior Left 917 -8 30 48 4.94 4.77

ITG, FFG Left 201 -40 -6 -40 3.75 3.36

MTG, posterior Left 2,438 -60 -50 -4 7.89 8.15

Occipital cortex Right 171 42 -72 18 5.09 5.81

Send questions, comments, or feedback to mtd3@duke.edu

Older Younger

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Phonological Semantic Perceptual

L

Semantic > Phonological Network

Phonological > Semantic Network

Phonological Regions Hemi

# Voxels X Y Z

Max Z Younger

Max Z Older

MFG, frontal pole Left 324 -34 38 26 5.99 5.36

MFG, frontal pole Right 521 34 38 32 3.87 4.25

Pre-central gyrus Left 3439 -50 -10 50 6.97 8.93*

Pre-central gyrus Right 488 52 -2 44 3.71 5.73*

Post-central gyrus Left 191 -64 -20 12 3.29 4.66*

Anterior Cingulate Bilat. 4,061 -4 0 54 6.73 8.48*

Anterior Insula Left 1,423 -24 22 4 6.12 6.05

Anterior Insula Right 1,511 28 40 22 4.70 5.54

Angular Gyrus Left 1,603 -30 -48 26 8.43 8.72

Angular Gyrus Right 66 44 -46 46 2.42 2.92

Occipital Cortex Bilat. 13,475 -12 -74 36 11.37 11.40

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Drift Rate Non-Decision Time

Reaction Time Accuracy

Phonological Network Semantic Network

=.42Age +.11fMRI +.06A x f =-.21Age +.41fMRI +.69A x f

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4 Results (Continued)

Age Related Differences in fMRI Activation

Relationships between Behavior, Age, & fMRI ActivationWe used linear regression in which Age Group, the average fMRI activation, and the interaction of Age Group and fMRI activation were independent variables (predictors), and drift rate was the outcome variable. For both networks, the overallmodels were significant. Phonological network: Model R2 = .21 no single predictor was significant.Semantic Network: Model R2 = .41 fMRI activation was a significant predictor.