Effect of Anodal tDCS on Articulatory Accuracy, Word Production, and Syllable Repetition in Subjects with Aphasia: A Crossover, Double-Blinded, Sham-Controlled Trial

Abstract

IntroductionTranscranial direct-current stimulation (tDCS) has been used to modulate and induce changes in brain function and excitability. tDCS is a promising tool for the treatment of aphasia.ObjectiveTo evaluate whether tDCS improves articulatory accuracy and speech production in patients with aphasia after stroke.Methods and ResultsTwelve right-handed subjects participated in a double-blind, sham-controlled, crossover offline trial. We assessed (1) articulatory accuracy at a naming task, (2) number of words correctly produced, (3) number of syllables repeated correctly, and (4) qualitative assessment of speech. Articulatory accuracy improved when using tDCS over Broca’s area in subjects with aphasia post-stroke (p ≤ 0.05). Qualitative improvement in the naming and syllable repetition tasks was observed, but the difference was not statistically significant (respectively, p = 0.15 and p = 0.79).ConclusionThe current results corroborate the potential of tDCS to be used as an alternative and complementary treatment for individuals with aphasia.

Adjunctive Approaches to Aphasia Rehabilitation: A Review on Efficacy and Safety

“…Similar to stroke motor function parameters, in tDCS studies, the electrode placement aims to restore the interhemispheric unbalance between the residual left language areas and the right hemispheric ones [ 157 , 158 ]. Thus, two broad approaches have been usually adopted: facilitation of activity in lesioned or perilesional areas through anodal stimulation [ 19 , 20 , 21 , 22 , 23 , 24 , 27 , 28 , 30 , 134 , 135 , 136 , 138 , 139 , 141 , 142 , 143 , 144 , 145 , 146 , 149 , 150 , 151 , 153 , 156 ] or inhibition of the intact right hemisphere to diminish abnormal transcallosal inhibition through cathodal stimulation [ 20 , 133 , 137 , 140 , 145 , 152 , 154 ]. There were no reported side effects in any of the studies, even when tDCS was applied in a multiple session paradigm [ 127 , 128 ].…”

“…Studies also included a mix of different types of aphasia classification (reporting either the patients’ scores or classifying their symptoms and/or considering their speech fluency) contributing to their extreme heterogeneity [ 127 ]. The classical modular approach has been most often adopted; thus, positioning the active electrode either over the left Broca’s area [ 19 , 21 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 132 , 135 , 142 , 144 , 145 , 150 , 151 , 156 ], the left Wernicke’s area [ 19 , 21 , 22 , 23 , 28 , 30 , 138 , 139 , 152 , 153 ] or the right homologues [ 20 , 133 , 137 , 145 , 147 , 152 , 154 , 155 ]. Indeed, most of the research has proven that anodal stimulation over these areas combined with language therapy increases different aspects of language.…”

“…More specifically, a significant improvement has been shown in noun naming after anodal tDCS over the left frontal gyrus [ 27 , 29 , 145 , 150 , 151 , 156 ] the left temporal gyrus [ 21 , 22 , 23 , 138 , 139 , 153 ] or the right homologues [ 137 , 145 , 152 , 154 ]. Some other studies have targeted the left inferior frontal gyrus in order to improve verb naming [ 21 , 23 , 27 , 28 , 29 , 148 ], speech fluency [ 27 , 28 , 29 , 30 ], repetition [ 24 , 25 , 26 , 135 ] and reading [ 142 ]. A couple of reports [ 147 , 155 ] have also investigated whether melodic intonation therapy (MIT) combined with anodal stimulation over the right inferior frontal gyrus would increase articulatory difficulties in post-stroke aphasia.…”

“…As reported in Table 3 , the studies were not homogeneous on the number of sessions included varying from one [ 136 , 141 , 143 , 144 , 151 ] to five [ 21 , 22 , 23 , 24 , 25 , 132 , 133 , 135 , 137 , 140 , 142 , 153 , 154 , 156 ] to fifteen sessions [ 26 , 138 , 139 , 147 ]. While for current intensity, there was a substantial agreement to use 1 mA [ 19 , 21 , 22 , 23 , 24 , 25 , 28 , 30 , 133 , 134 , 135 , 138 , 139 , 141 , 143 , 146 , 148 , 149 , 152 , 153 , 156 ] to 2 mA [ 20 , 26 , 27 , 29 , 132 , 133 , 136 , 137 ,…”

“…While for current intensity, there was a substantial agreement to use 1 mA [ 19 , 21 , 22 , 23 , 24 , 25 , 28 , 30 , 133 , 134 , 135 , 138 , 139 , 141 , 143 , 146 , 148 , 149 , 152 , 153 , 156 ] to 2 mA [ 20 , 26 , 27 , 29 , 132 , 133 , 136 , 137 , 140 , 142 , 144 , 145 , 147 , 151 , 154 ]. Unfortunately, almost half of the reported studies did not include follow-up sessions [ 19 , 27 , 30 , 132 , 136 , 141 , 143 , 144 , 148 , 151 , 154 , 155 ] and, in the remaining studies, tDCS effects were measured up to 1–4 weeks after the treatment [ 20 , 21 , 22 , 23 , 25 …”