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PLoS One. 2016 Feb 22;11(2):e0148707. doi: 10.1371/journal.pone.0148707. eCollection 2016.

The Brain Network of Naming: A Lesson from Primary Progressive Aphasia.

Author information

1
Institut du Cerveau et de la Moelle Epinière, UMR INSERM-CNRS-UPMC 1127, Frontlab, Paris, France.
2
Department of Neurology, National Reference Center for « PPA and rare dementias », Pitié Salpêtrière Hospital, AP-HP, Paris, France.
3
Centre de Neuro-imagerie de Recherche (CENIR), Institut du Cerveau et de la Moëlle Epinière, Paris, France.
4
Université Pierre et Marie Curie, INSERM, UMR-S 678, Paris, France.
5
Service de Neuroradiologie Diagnostique et Fonctionnelle, Hôpital de la Pitié-Salpêtrière, AP-HP, Paris, France.
6
Department of Neurology, Hôpital Saint Antoine, AP-HP, Paris, France.

Abstract

OBJECTIVE:

Word finding depends on the processing of semantic and lexical information, and it involves an intermediate level for mapping semantic-to-lexical information which also subserves lexical-to-semantic mapping during word comprehension. However, the brain regions implementing these components are still controversial and have not been clarified via a comprehensive lesion model encompassing the whole range of language-related cortices. Primary progressive aphasia (PPA), for which anomia is thought to be the most common sign, provides such a model, but the exploration of cortical areas impacting naming in its three main variants and the underlying processing mechanisms is still lacking.

METHODS:

We addressed this double issue, related to language structure and PPA, with thirty patients (11 semantic, 12 logopenic, 7 agrammatic variant) using a picture-naming task and voxel-based morphometry for anatomo-functional correlation. First, we analyzed correlations for each of the three variants to identify the regions impacting naming in PPA and to disentangle the core regions of word finding. We then combined the three variants and correlation analyses for naming (semantic-to-lexical mapping) and single-word comprehension (lexical-to-semantic mapping), predicting an overlap zone corresponding to a bidirectional lexical-semantic hub.

RESULTS AND CONCLUSIONS:

Our results showed that superior portions of the left temporal pole and left posterior temporal cortices impact semantic and lexical naming mechanisms in semantic and logopenic PPA, respectively. In agrammatic PPA naming deficits were rare, and did not correlate with any cortical region. Combined analyses revealed a cortical overlap zone in superior/middle mid-temporal cortices, distinct from the two former regions, impacting bidirectional binding of lexical and semantic information. Altogether, our findings indicate that lexical/semantic word processing depends on an anterior-posterior axis within lateral-temporal cortices, including an anatomically intermediate hub dedicated to lexical-semantic integration. Within this axis our data reveal the underpinnings of anomia in the PPA variants, which is of relevance for both diagnosis and future therapy strategies.

PMID:
26901052
PMCID:
PMC4764674
DOI:
10.1371/journal.pone.0148707
[Indexed for MEDLINE]
Free PMC Article

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