Bihemispheric stimulation over left and right inferior frontal region enhances recovery from apraxia of speech in chronic aphasia

Abstract

Several studies have already shown that transcranial direct current stimulation (tDCS) is a useful tool for enhancing recovery in aphasia. However, all tDCS studies have previously investigated the effects using unihemisperic stimulation. No reports to date have examined the role of bihemispheric tDCS on aphasia recovery. Here, eight aphasic persons with apraxia of speech underwent intensive language therapy in two different conditions: real bihemispheric anodic ipsilesional stimulation over the left Broca's area and cathodic contralesional stimulation over the right homologue of Broca's area, and a sham condition. In both conditions, patients underwent concurrent language therapy for their apraxia of speech. The language treatment lasted 10 days (Monday to Friday, then weekend off, then Monday to Friday). There was a 14-day intersession interval between the real and the sham conditions. In all patients, language measures were collected before (T0), at the end of (T10) and 1 week after the end of (F/U) treatment. Results showed that after simultaneous excitatory stimulation to the left frontal hemisphere and inhibitory stimulation to the right frontal hemisphere regions, patients exhibited a significant recovery not only in terms of better accuracy and speed in articulating the treated stimuli but also in other language tasks (picture description, noun and verb naming, word repetition, word reading) which persisted in the follow-up session. Taken together, these data suggest that bihemispheric anodic ipsilesional and cathodic contralesional stimulation in chronic aphasia patients may affect the treated function, resulting in a positive influence on different language tasks.

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

“…These data seem to contradict previous results by Marangolo et al [15,16] where the improvement in articulation resulted from excitatory stimulation over the left IFG. However, while in those studies tDCS stimulation was combined with a traditional treatment for articulatory disorders [15,16], in the present study, the MIT approach involved both melodic and rhythmic aspects of music which, as previously stated, are likely subserved by right hemispheric structures [30,41,42]. In Combining TMS-EEG with tDCS 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.…”

“…Also, follow-up testing revealed that the improvement in response accuracy persisted up to 2 months after treatment and generalized in different oral and writing tasks (i.e., repetition, reading and writing under dictation). More recently, the authors wondered if similar results would be achieved using bihemispheric tDCS delivered over the left and right IFG [16]. Eight aphasic persons with apraxia of speech (AOS) underwent intensive language treatment in two different conditions: real anodic ipsilesional stimulation over the left Broca's area and cathodic contralesional stimulation over the right homolog of Broca's area, and a sham condition.…”

Current Evidence for Post Stroke Aphasia Treatment

“…Several studies applied anodal tDCS to the left Broca's or Wernicke's areas and another study applied cathodal tDCS to the right homologous Broca's area [32][33][34][35][36]. Another study used dual tDCS with an anodal electrode over the left Broca's area and a cathodal electrode over the right Broca's homologue area [37]. In this systematic 4/7 https://doi.org/10.12786/bn.2017.10.e15…”

Ipsilesional and contralesional regions participate in the improvement of poststroke aphasia: a transcranial direct current stimulation study

“…Dual tDCS was also used in studies regarding the visual and working memory of healthy subjects (Chi, Fregni, & Snyder, 2010;Sandrini, Fertonani, Cohen, & Miniussi, 2012). Recently, bihemispheric stimulation was used successfully in a group of eight patients with apraxia of speech (Marangolo et al, 2013) and in a single-case study, together with a verb anomia training (Manenti et al, 2014). In this last report (Manenti et al, 2014), after 20 sessions of bihemispheric stimulation on dorsolateral prefrontal cortex (DLPFC) (tDCS anodal was placed on the left DLPFC and tDCS cathodal was placed on the right DLPFC), an aphasic patient achieved an improvement in treated and untreated verbs naming and the effect lasted up to 48 weeks after the end of stimulation.…”