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Poster D40, Thursday, November 9, 6:15 – 7:30 pm, Harborview and Loch Raven Ballrooms

Semantic activity differs during comprehension and production of sentences

Clara Scholl1, Alice Jackson1, Michael Wolmetz1;1Johns Hopkins University Applied Physics Laboratory

Research on the characteristics and organization of the cortical semantic network has largely focused on semantics during recognition and comprehension. Experimental paradigms and deficit patterns associated with retrieving semantic information to understand pictures and words have yielded increasingly sharp descriptions of the cortical semantic network, but how these descriptions relate to semantic processing for production and communication is not well understood. To begin to address this gap, we used functional Magnetic Resonance Imaging (fMRI) to compare patterns of semantic activity during sentence production and sentence comprehension. After training to type in the scanner, participants (N = 21, mean age = 28) typed sentences about cued topics (e.g. castles) over the course of three functional runs using an MR-safe keyboard, and then participants read short passages on the same topics over the course of three functional runs. The same twelve topics appeared in each run, in a randomized order. Semantic responses during production were compared with semantic responses during comprehension using Representational Similarity Analysis (RSA). Dissimilarity Matrices (DSMs) were calculated at searchlight locations throughout the brain for data collected during the production condition, and separately for the comprehension condition. These DSMs were directly compared to one another, but also compared to a model of the semantic relatedness between stimulus topics based on behavioral ratings collected on Amazon Mechanical Turk. Using these techniques, we observed semantic neural activity patterns associated with the comprehension condition that was consistent with related studies. Many regions, including bilateral superior temporal gyri, bilateral precentral gyri, left middle temporal gyrus, left inferior frontal gyrus, and left cingulate gyrus, had response patterns that significantly correlated with behavior-based semantic relatedness. Semantic neural activity patterns associated with the production data was substantially more variable across subjects, due in part to variability in behavioral responses. There are many challenges in adapting the methods and analysis techniques built for studying cued recognition and language comprehension to questions about language production and communication. This work represents a first step toward studying more naturalistic modes of communication, and extending models of the cortical semantic network to language production.

Topic Area: Meaning: Discourse and Pragmatics

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