Slide Slam Q13
The relationship between memory and sentence processing in the aging brain
Nicholas Riccardi1, Rutvik Desai1, Sara Sayers2, Sarah Newman-Norlund2, Samaneh Nemati2, Roger Newman-Norlund1, Julius Fridriksson2; 1University of South Carolina, Department of Psychology, 2University of South Carolina, Department of Communication Sciences and Disorders
Introduction: Healthy aging is associated with subtle declines in sentence processing that have been linked to structural and functional properties of the brain. Age is also related to a decline in memory abilities that contribute to sentence processing, providing a useful model to study the relationship between memory, sentence processing, and the brain. Here, we examined the relationship between grey matter volume (GMV) and white matter connectivity measured using diffusion tensor imaging (DTI) with sentence processing, working memory (WM), auditory-verbal memory (AVM), and phonological short-term memory (PSTM) in a group of healthy older adults. Methods: Sixty participants (40 Female, 20 Male) between the ages of 60 and 80 (M = 66.78, SD = 6.98) were recruited as part of the Aging Brain Cohort Study at the University of South Carolina. Participants completed a sentence repetition task with 30 sentences, and three memory tasks from the National Institutes of Health (NIH) cognitive battery. In the WM task, animal and food words and pictures are shown to participants, who must then repeat back the items in order from smallest to largest. In the AVM task, a list of fifteen unrelated words is read aloud to participants, who must then repeat as many words back as they can. In the PSTM test, participants must repeat pronounceable nonwords of increasing length. Structural MRI scans were collected. Voxel-based morphometry (VBM) was used to determine where GMV was associated with memory and sentence processing within a bilateral mask consisting of inferior frontal gyrus pars opercularis and triangularis (IFGoper, IFGtri), supramarginal and angular gyri (SMG, AG), and posterior middle and superior temporal gyri (pMTG, pSTG). Additionally, a connectivity matrix of fiber counts between areas within this network was created for each participant from DTI scans. Structural correlates of sentence and memory tasks were examined first. Next, sentence repetition, controlling for memory, was analyzed by adding all memory tasks as nuisance regressors. All analyses controlled for age and family-wise error (FWE) error corrected (p < .05) unless otherwise noted. Results: All 3 memory tasks were correlated with sentence repetition (p < .05). VBM revealed clusters in right AG, pMTG, and bilateral IFGtri that were associated with worse WM performance (p < .001, uncorrected). A cluster in the right AG was associated with AVM (p < .001, uncorrected). Sentence repetition was associated with clusters in the left SMG and bilateral IFGtri (FWE, p < .05). When controlling for memory tasks, a cluster in the left SMG was associated with sentence repetition performance (FWE, p < .05). DTI revealed greater connectivity between the left SMG and pMTG was related to better sentence repetition, even after controlling for memory tasks. Conclusions: WM, AVM, and PSTM abilities are associated with sentence processing in older adults. VBM and DTI revealed that structural properties of the left SMG are related to sentence repetition independently of memory. We interpret this as reflecting the high sensory-motor integration demands of sentence processing compared to the other tasks, in which the left SMG plays a critical role.