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Cortex. 2017 Aug;93:92-106. doi: 10.1016/j.cortex.2017.04.016. Epub 2017 Apr 29.

Semantic word category processing in semantic dementia and posterior cortical atrophy.

Author information

1
Medical Research Council, Cognition and Brain Sciences Unit, Cambridge, UK; Linguistics Department, College of Humanities and Social Sciences, United Arab Emirates University, United Arab Emirates. Electronic address: zubaida.shebani@uaeu.ac.ae.
2
Medical Research Council, Cognition and Brain Sciences Unit, Cambridge, UK; Department of Clinical Neurosciences, University of Cambridge, UK.
3
German Center for Neurodegenerative Diseases (DZNE), Magdeburg, Germany.
4
Department of Clinical Neurosciences, University of Cambridge, UK; Tecnalia Research and Innovation Center, Health Division, Neurotechnology Unit, Bizkaia Technology Park, Derio, Spain.
5
Department of Clinical Neurosciences, University of Cambridge, UK.
6
Medical Research Council, Cognition and Brain Sciences Unit, Cambridge, UK; Brain Language Laboratory, Department of Philosophy and Humanities, WE4, Freie Universität Berlin, Berlin, Germany; Berlin School of Mind and Brain, Humboldt Universität zu Berlin, Berlin, Germany; Einstein Center for Neurosciences, Berlin, Germany. Electronic address: f.p@fu-berlin.de.

Abstract

There is general agreement that perisylvian language cortex plays a major role in lexical and semantic processing; but the contribution of additional, more widespread, brain areas in the processing of different semantic word categories remains controversial. We investigated word processing in two groups of patients whose neurodegenerative diseases preferentially affect specific parts of the brain, to determine whether their performance would vary as a function of semantic categories proposed to recruit those brain regions. Cohorts with (i) Semantic Dementia (SD), who have anterior temporal-lobe atrophy, and (ii) Posterior Cortical Atrophy (PCA), who have predominantly parieto-occipital atrophy, performed a lexical decision test on words from five different lexico-semantic categories: colour (e.g., yellow), form (oval), number (seven), spatial prepositions (under) and function words (also). Sets of pseudo-word foils matched the target words in length and bi-/tri-gram frequency. Word-frequency was matched between the two visual word categories (colour and form) and across the three other categories (number, prepositions, and function words). Age-matched healthy individuals served as controls. Although broad word processing deficits were apparent in both patient groups, the deficit was strongest for colour words in SD and for spatial prepositions in PCA. The patterns of performance on the lexical decision task demonstrate (a) general lexicosemantic processing deficits in both groups, though more prominent in SD than in PCA, and (b) differential involvement of anterior-temporal and posterior-parietal cortex in the processing of specific semantic categories of words.

KEYWORDS:

Category specificity; Posterior Cortical Atrophy; Semantic Dementia; Semantics; Word processing

PMID:
28624681
PMCID:
PMC5542041
DOI:
10.1016/j.cortex.2017.04.016
[Indexed for MEDLINE]
Free PMC Article

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