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Poster E22, Friday, November 10, 10:00 – 11:15 am, Harborview and Loch Raven Ballrooms

An adaptive semantic matching paradigm for reliable and valid language mapping in individuals with aphasia

Melodie Yen1, Dana K. Eriksson2, Andrew T. DeMarco3, Stephen M. Wilson1;1Vanderbilt University Medical Center, 2University of Arizona, 3Georgetown University

Recovery from aphasia depends on neural plasticity, that is, functional reorganization of surviving brain regions such that they take on new or expanded roles in language processing. A significant roadblock to understanding this process is that it is challenging to identify language regions in individuals with aphasia. Tasks commonly used to engage language processing, such as narrative comprehension and picture naming, are limited in terms of reliability (test-retest reproducibility) and validity (identification of language regions, and not other regions). On the other hand, paradigms that are effective in identifying language regions in people without aphasia (for instance, semantic decision tasks in presurgical patients) are often too challenging for people with aphasia. We designed an adaptive semantic matching task whereby each individual is presented with dynamically selected stimuli that are challenging yet within their competence, so that language processing can be fully engaged in people with and without language disorders. In this study, we evaluated the feasibility, reliability and validity of this adaptive semantic matching paradigm. Experiment 1: Sixteen individuals with chronic aphasia each performed the semantic task, a narrative comprehension task, and a picture naming task, on two separate occasions. We found that all patients succeeded in learning and performing the semantic task. Left-lateralized frontal and temporal regions were robustly activated, except when these regions were lesioned. The consistency of activation patterns across the two sessions were compared in terms of Dice coefficients of similarity. The semantic paradigm resulted in more reproducible patterns of activation (Dice coefficient = 0.59 ± 0.15) than the narrative (0.38 ± 0.15) or picture naming (0.32 ± 0.20) paradigms (both p < 0.0001). Experiment 2: To assess validity (defined as ability to demonstrate left-lateralized language networks in neurologically normal individuals), thirteen healthy controls performed the same three tasks. We found that the adaptive semantic matching paradigm produced much more left-lateralized activation patterns (Lateralization index = 0.75 ± 0.19) than the narrative (0.32 ± 0.36) or picture naming (0.05 ± 0.20) paradigms (both p < 0.0001). Experiment 3: To determine whether different kinds of linguistic processing would highlight different parts of the language network, we developed two adaptive phonological matching tasks (syllable count matching and rhyme judgment) with the same structure as the semantic paradigm. Seven healthy controls performed the semantic task and the two phonological tasks. Core language regions in the left inferior frontal gyrus and left posterior superior temporal sulcus were activated in common by all three tasks. However, there were significant differences between the semantic and phonological tasks, with the semantic task differentially recruiting a broad range of additional left temporal regions (p < 0.05, corrected), while the phonological tasks differentially recruited the left ventral precentral sulcus and supramarginal gyrus (p < 0.05, corrected). Activations for the phonological tasks were not as robust as for the semantic task in individual participants. In sum, the adaptive semantic matching task makes it possible to identify language regions in individuals with aphasia, and will be useful in future studies of neural plasticity in recovery from aphasia.

Topic Area: Language Disorders

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