tDCS over the left inferior frontal cortex improves speech production in aphasia

Abstract

In this study, we investigated the combined effect of transcranial direct current stimulation (tDCS) and an intensive Conversational therapy treatment on discourse skills in 12 persons with chronic aphasia. Six short video clips depicting everyday life contexts were prepared. Three videoclips were used to elicit spontaneous conversation during treatment. The remaining three were presented only before and after the therapy. Participants were prompted to talk about the contents of each videoclip while stimulated with tDCS (20 min 1 mA) over the left hemisphere in three conditions: anodic tDCS over the Broca's area, anodic tDCS over the Wernicke's area, and a sham condition. Each experimental condition was performed for 10 consecutive daily sessions with 14 days of intersession interval. After stimulation over Broca's area, the participants produced more Content Units, verbs and sentences than in the remaining two conditions. Importantly, this improvement was still detectable 1 month after the end of treatment and its effects were generalized also to the three videoclips that had been administered at the beginning and at the end of the therapy sessions. In conclusion, anodic tDCS applied over the left Broca's area together with an intensive “Conversational Therapy” treatment improves informative speech in persons with chronic aphasia. We believe that positive tDCS effects may be further extended to other language domains, such as the recovery of speech production.

The effect of lexical deficits on narrative disturbances in fluent aphasia

“…Indeed, the analysis of their lexical skills showed that they produced significantly more phonological errors and more semantic paraphasias than the controls. This is not a new finding, as failure to spontaneously produce fluent and informative speech is the most persistent disabling consequence in persons with aphasia (e.g., Fergadiotis, Wright, & West, 2013;Marangolo et al, 2013;Taylor-Sarno, 1998). Interestingly, a qualitative inspection of the phonological errors showed that these were mostly false starts with fewer phonological paraphasias and neologisms.…”

Combining TMS-EEG with transcranial direct current stimulation language treatment in aphasia

“…In contrast, cathodal tDCS decreases cortical excitability, shifting the resting membrane potential toward hyperpolarization and reducing the firing rate of neurons [7][8][9]. A small but growing body of evidence has already indicated that tDCS may provide a supplementary treatment approach for different language deficits in patients with chronic stroke-induced aphasia, such as word-finding difficulties [10][11][12][13], non-fluent speech [12,14] and articulatory disorders [15][16][17][18][19]. In fact, in a preliminary study on a small sample of chronic patients, Marangolo et al [15] showed that repetitive anodal tDCS over the left inferior frontal gyrus (IFG), coupled with language training helped patients to recover from their articulatory disturbances.…”

Use of Computational Modeling to Inform tDCS Electrode Montages for the Promotion of Language Recovery in Post-stroke Aphasia

“…Thus, the design and interpretation of most of the research addressed only the current delivered over the targeted region. This led to two neuromodulation strategies: either increasing excitability through anodal stimulation over the left hemisphere [5][6][7][8][9]11,[13][14][15][16]20,21] or by decreasing excitability in the contralesional language homologue areas using cathodal stimulation in order to attenuate the inhibition from the intact right hemisphere [10,12,15,[17][18][19][20]. Indeed, while in the context of acute or subacute lesions of the left hemisphere language network there appears to be greater tendency for reallocation of language function into the right-hemisphere perisylvian circuits, many studies have shown that, over time, there is, for a number of patients at least, diminished recruitment of right hemisphere structures for language tasks with a redistribution of language processing back to the left hemispheric perisylvian areas [22][23][24].…”

“…While the first published study [4] that documented tDCS use for aphasia rehabilitation did not include a behavioral treatment protocol, studies since then have combined tDCS with speech-language therapy [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. These initial studies generally included behavioral treatment for anomia and implemented noun retrieval as the outcome measure; more recent studies have included additional behavioral treatments for the recovery of verbs [5,7,13], articulation [9] and discourse productivity [6,8]. However, although the behavioral treatment component has progressed from its initial focus on word retrieval, the electrode montages implemented for the administration of tDCS have remained consistent over time.…”