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Abstract

Word finding difficulties are common in Alzheimer’s disease (AD) and are a defining feature of primary progressive aphasia. Using fMRI we examined the underlying pathogenetic mechanisms based on a modified version of the Pyramids and Palm Trees test. In more than 100 cognitvely intact older adults we first defined the network structure by means of graph analysis. Next we evaluated which nodes are most vulnerable from the preclinical  (as defined based on amyloid imaging) over the amnestic MCI to the early dementia stage of Alzheimer’s disease: the posterior third of the left superior temporal sulcus and the middle temporal gyrus are the areas of predilection. In contrast, anterior temporal cortex is mainly affected in PPA semantic variant. We further examined the contribution of this region to semantic processing in the intact brain:  in left perirhinal cortex, overlapping with the region affected in PPA SV, semantic similarity between concrete entities represented as words was reflected by the cosine similarity between fMRI response patterns to these words, indicative for a role in semantic coding. High-level mathematical approaches and the application of a common fMRI paradigm across different populations provides novel insights in the associative-semantic network.

Hosts: Celine Gillebert and Kia Nobre

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