• Charlotte Rosso, R Valabregue, C Arbizu, S Ferrieux, P Vargas, F Humbert, Y Attal, A Messé, C Zavanone, S Meunier, L Cohen, C Delmaire, A Thielscher, D M Herz, H R Siebner, Y Samson, and S Lehéricy.
• CRICM - Centre de Recherche de l'Institut du Cerveau et de la Moelle épinière, UPMC Paris 6, Paris, France; Inserm, U975, CNRS, UMR 7225 Paris, France; COGIMAGE, UPMC Paris 6, Paris, France; APHP, Urgences Cérébro-Vasculaires, Hôpital Pitié-Salpêtrière, Paris, France; Univ Paris 11, IFR49, DSV/I2BM/NeuroSpin, Bat 145, Gif-sur-Yvette 91191, France. Electronic address: charlotte.rosso@gmail.com.
• Brain Stimul. 2014 Jan 1;7(1):122-9.

BackgroundCathodal transcranial direct current stimulation (tDCS) of the right frontal cortex improves language abilities in post-stroke aphasic patients. Yet little is known about the effects of right frontal cathodal tDCS on normal language function.Objective/HypothesisTo explore the cathodal tDCS effects of the right-hemispheric homologue of Broca's area on picture naming in healthy individuals. We hypothesized that cathodal tDCS improves picture naming and that this effect is determined by the anatomical and functional connectivity of the targeted region.MethodsCathodal and sham tDCS were applied to the right inferior frontal gyrus in 24 healthy subjects before a picture-naming task. All participants were studied with magnetic resonance imaging at pre-interventional baseline. Probabilistic tractography and dynamic causal modeling of functional brain activity during a word repetition task were applied to characterize anatomical and functional connectivity.ResultsSubjects named pictures faster after cathodal relative to sham tDCS. The accelerating effect of tDCS was explained by a reduced frequency of very slow responses. tDCS-induced acceleration of picture naming correlated with larger volumes of the tract connecting the right Broca's area and the supplementary motor area (SMA) and greater functional coupling from the right SMA to the right Broca's area.ConclusionsThe results support the notion that the after-effects of tDCS on brain function are at least in part determined by the anatomical and functional connectivity of the targeted region.Copyright © 2014 Elsevier Inc. All rights reserved.

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