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Poster D28, Thursday, November 9, 6:15 – 7:30 pm, Harborview and Loch Raven Ballrooms

Sentence Repetition Impairment in Primary Progressive Aphasia: A Voxel-Based Morphometry (VBM) study

Sladjana Lukic1, Maria Luisa Mandelli1, Ariane Welch1, Yann Cobigo1, H. Isabel Hubbard1, Maria Luisa Gorno-Tempini1;1Memory and Aging Center, Department of Neurology, University 
of California San Francisco

Introduction: During repetition tasks, humans engage their speech production system, retaining phonemes, syntax and semantics in short-term memory. Previous studies indicate that repetition is affected in patients with primary progressive aphasia (PPA), particularly in the logopenic variant PPA, and it is associated with atrophy in the left posterior temporal and parietal regions [1-3]. However, repetition deficits may result from breakdown at any level of processing, and have not yet been thoroughly investigated. The purpose of this study was to examine how gray matter (GM) atrophy contributes to sentence repetition performance in PPAs with non-fluent (nfvPPA), logopenic (lvPPA) and semantic variant (svPPA). Of particular interest was evaluating how processing long or short and meaningful or non-meaningful phrases, contribute to repetition performance in PPAs. Method: 86 PPAs (25 nfvPPA, 42 lvPPA, and 19 svPPA; Age range = 51 – 84, mean = 64.9; 52 females) were classified into three subtypes based on published criteria [4]. All performed the repetition task comprised of 20 phrases that varied in length and meaning (a shorter version of Bayles test [5]). The patients’ T1 images were pre-processed using a standard VBM procedure: segmentation (gray and white matter), normalization, modulation, and 8mm Gaussian kernel smoothing. Using regression models, we tested: (1) the effects of length and meaning on repetition performance in PPA variants, (2) the relation between GM volume and repetition performances across PPA variants, and (3) group differences in GM volume in regions-of-interest (ROIs) where PPAs showed a significant relation between GM volume and repetition performances. Age, total intracranial volume, and sex were included as covariates in the model. Significance was set at p < 0.05 corrected for multiple comparisons. Results: The regression analyses revealed: (1) poorer performance for longer and non-meaningful phrases across PPA variants. LvPPA performed worst across all phrases, svPPA in long phrases, and nfvPPA did not show any repetition deficits. (2) Decreased performance on long meaningful phrases was associated with atrophy in the bilateral planum temporale (PT), superior and middle temporal gyri (STG, MTG). Left-lateralized PT, MTG, STG, and thalamus atrophy were associated with poor performance on non-meaningful phrases, short or long. No areas were associated with performance on short meaningful phrases. (3) Finally, ROI analysis showed decreased GM volume in the bilateral PT and STG for lvPPA when compared to nfvPPA or svPPA variants. Also, lvPPA showed decreased GM volume in the bilateral MTG and the right thalamus when compared to nfvPPA and svPPA, respectively. No differences in GM volume were found between the latter two. Conclusions: The data showed that longer and non-meaningful phrases were the hardest across PPAs. Decreased GM volume within the bilateral temporal regions contributed to impairment on repetition tasks in lvPPA, providing direct evidence that these regions are implicated in the phonological anatomical network. This study showed that specific neuroanatomical and linguistic features of repetition tasks could inform the diagnosis of logopenic and semantic variant PPA. Eventually, these findings may provide some insights to distinguish the different processes, such as semantics or phonology that underlie repetition.

Topic Area: Language Disorders

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