1. 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. Diaz 1,2, Micah A. Johnson 1, Anthony Pecoraro 1, Deborah M. Burke 3, and David J. Madden 1,2 1 Brain Imaging & Analysis Center, Duke University Medical Center, 2 Department of Psychiatry & Behavioral Sciences, Duke University Medical Center, 3 Department of Linguistics and Cognitive Science, Pomona College 1 Introduction The 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 Networks Our 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 mm 3 ) Preprocessing and analysis with FSL (cluster corrected, GRF theory, p<.001) Results from higher-level comparisons were masked by lower level comparisons YoungerOlder N19 Age*25 (4.9)67.5 (5.4) Education16.4 (2.1)17.2 (2.0) MMSE29.2 (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 Recall11.7 (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 RegionsHemi# VoxelsXYZ Max Z Younger Max Z Older IFGLeft2,588-4438-187.527.58 IFGRight6615426106.206.65 Orbital-frontal CtxRight274434-162.001.67 MFG, posteriorLeft833-4016505.325.42 SFG, posteriorLeft917-830484.944.77 ITG, FFGLeft201-40-6-403.753.36 MTG, posteriorLeft2,438-60-50-47.898.15 Occipital cortexRight17142-72185.095.81 Send questions, comments, or feedback to mtd3@duke.edu Older Younger ** Phonological Semantic Perceptual L Semantic > Phonological Network Phonological > Semantic Network Phonological RegionsHemi # VoxelsXYZ Max Z Younger Max Z Older MFG, frontal poleLeft324-3438265.995.36 MFG, frontal poleRight5213438323.874.25 Pre-central gyrusLeft3439-50-10506.978.93* Pre-central gyrusRight48852-2443.715.73* Post-central gyrusLeft191-64-20123.294.66* Anterior CingulateBilat.4,061-40546.738.48* Anterior InsulaLeft1,423-242246.126.05 Anterior InsulaRight1,5112840224.705.54 Angular GyrusLeft1,603-30-48268.438.72 Angular GyrusRight6644-46462.422.92 Occipital CortexBilat.13,475-12-743611.3711.40 ** Drift Rate Non-Decision Time Reaction Time Accuracy Phonological Network Semantic Network =.42Age +.11fMRI +.06A x f =-.21Age +.41fMRI +.69A x f ** 4 Results (Continued) Age Related Differences in fMRI Activation Relationships between Behavior, Age, & fMRI Activation We 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 overall models were significant. Phonological network: Model R 2 =.21 no single predictor was significant. Semantic Network: Model R 2 =.41 fMRI activation was a significant predictor.