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Poster C57, Thursday, November 9, 10:00 – 11:15 am, Harborview and Loch Raven Ballrooms

The intensity of sensory-perceptual features regulates conceptual processing in the anterior temporal lobe’s semantic hub

Jet M. J. Vonk1,2, H. Isabel Hubbard2, Maria Luisa Mandelli2, Roel Jonkers3, Adam M. Brickman4, Bruce L. Miller2, Maria Luisa Gorno-Tempini2, Loraine K. Obler1;1The Graduate Center of the City University of New York, 2Memory and Aging Center, University of California San Francisco, 3University of Groningen, 4The Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Columbia University

The components of semantic representations include sensory-perceptual information. In the hub-and-spoke model these representations emerge from a central trans-modal hub, based in the anterior temporal lobe (ATL), that incorporates input from sensory-perceptual regions (e.g., Patterson et al., 2007). Little is known about the influence of sensory-perceptual features on the intensity of semantic processing in this region. Structural MRI allowed us to investigate whether the involvement of the ATL is dependent on the degree of semantic association with sensory-perceptual information by assessing the relation between regional volume and behavioral lexical-semantic performance in individuals with primary progressive aphasia (PPA). Individuals with the semantic variant (svPPA; atrophy in ATL), generally show a wide-spread semantic deficit, while individuals with the non-fluent variant (nfvPPA; atrophy in premotor cortex) and logopenic variant (lvPPA; atrophy in temporo-parietal cortex) are characterized by intact single-word processing and no semantic impairment. From a set of 350 words—controlled on a broad range of psycholinguistic and semantic variables—the 22 highest and 22 lowest associated words (rated by 242 healthy adults) on each of six noun and six verb sensory-perceptual features were selected. Features for nouns were visual motion, sound, color, manipulation, smell/taste, and shape and those for verbs were mouth use, hand use, leg use, change of state, visual motion and sound. Lexical decision performance and T1-weighted MR images of 37 individuals with nfvPPA (N = 11), lvPPA (N = 13), and svPPA (N = 13), as well as 17 age-matched controls, were analyzed with voxel-based morphometry (VBM) to identify the association between cortical volume and performance on high- and low-association words. Behaviorally, individuals with svPPA showed no differences between high- and low-association items on any of the noun features and performed significantly worse than controls on all high-association noun- and verb-features, demonstrating a general trans-modal semantic impairment. In contrast, those with nfvPPA and lvPPA displayed moderate sensory-perceptual specific impairments, especially for motor-actions and sound words, respectively. Performance on high- and low-association items for eleven of the twelve sensory-perceptual features was associated with lower volume in the left and/or right ATL(s), while there was no other brain region that was similarly consistently involved across features. For nine of the sensory-perceptual features, the involvement of the ATL remained significant after the VBM statistical map of the high-association words was masked by the VBM statistical map of the low-association words. This masking eliminated effects of equivalent properties of the high- and low-association words, isolating the specific influence of each feature. Hence, the results indicate a stronger correlation of the ATL with impairment on high-association words than low-association words. This study supports the central trans-modal hub role of the ATL, impaired in individuals with svPPA in contrast with the specific sensory-perceptual impairments in individuals with nfvPPA and lvPPA. Results demonstrate that the processing intensity of semantic representations in the ATL is regulated by a concept’s degree of association with sensory-perceptual information. This finding expands the idea of the ATL as an active hub that integrates the variable input from sensory-perceptual regions into holistic conceptual representations.

Topic Area: Meaning: Lexical Semantics

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