The White Matter Module-Hub Network of Semantics Revealed by Semantic Dementia

Martina Sundqvist (1, 2, 3, 4, 5, 6) , Alexandre Routier (2, 1) , Bruno Dubois (1, 7) , Olivier Colliot (2) , Marc Teichmann (1, 7)

1 FRONTlab - Equipe Fonctions et dysfonctions de systèmes frontaux [ICM Paris]
2 ARAMIS - Algorithms, models and methods for images and signals of the human brain = Algorithmes, modèles et méthodes pour les images et les signaux du cerveau humain [ICM Paris]
3 INRAE - Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement
4 Institut Curie [Paris]
5 PSL - Université Paris sciences et lettres
6 MIA Paris-Saclay - Mathématiques et Informatique Appliquées
7 CHU Pitié-Salpêtrière [AP-HP]

2AbstractCognitive neuroscience exploring the architecture of semantics has shown that coherent supra-modal concepts are computed in the anterior temporal lobes (ATL) but it is unknown how/where modularinformation implemented by posterior cortices (word/object/face forms) is conveyed to the ATL hub. We investigated the semantic module-hub network in healthy adults (N = 19) and in semantic dementia patients (N = 28) by combining semantic assessments of verbal and non-verbal stimuli and MRI-based fiber tracking usingseeds in three module-related cortices implementing i) written word forms (‘Visual Word Form Area’), ii) abstract lexical representations (posterior-superior temporal cortices), and iii) face/object representations (‘Face Form Area’).Fiber tracking revealed three key tracts linking the ATL with the three module-related cortices. Correlation analyses between tract parameters and semantic scores indicated that the three tracts subserve semantics, transferring modular verbal or non-verbal object/face information to the left and right ATL, respectively. The module-hub tracts were functionally and micro-structurally damaged in semantic dementia whereas damage to non-module specific ATL tracts (inferior longitudinal fasciculus, uncinate fasciculus) had more limited impact on semantic failure. These findings identify major components of the white matter module-hub network of semantics and they corroborate/materialize claims of cognitive models positing direct links between modular and semantic representations. In combination with modular accounts of cognition, they also suggest that the currently prevailing ‘hub-and-spokes’ model of semantics could be extended by incorporating an intermediate module level containing invariant representations, in addition to ‘spokes’ which subserve the processing of a near-unlimited number of sensori-motor and speech-sound features.

Mots clés: Semantic dementia; Semantics; Diffusion MRI; Tractograghy

Domaines: Imagerie médicale

Martina Sundqvist, Alexandre Routier, Bruno Dubois, Olivier Colliot, Marc Teichmann. The White Matter Module-Hub Network of Semantics Revealed by Semantic Dementia. Journal of Cognitive Neuroscience, 2020, pp.1-18. ⟨10.1162/jocn_a_01549⟩. ⟨hal-02554966⟩