Bilateral Transcranial Direct Current Stimulation Language Treatment Enhances Functional connectivity in the Left Hemisphere: Preliminary data from Aphasia.

Several studies have already shown that transcranial direct current stimulation (tDCS) is a useful tool for enhancing recovery in aphasia. However, no reports to date have investigated func- tional connectivity changes on cortical activity because of tDCS language treatment. Here, nine aphasic persons with articulatory disorders underwent an intensive language therapy in two differ- ent conditions: bilateral anodic stimulation over the left Broca’s area and cathodic contralesional stimulation over the right homo- logue of Broca’s area and a sham condition. The language treat- ment lasted 3 weeks (Monday to Friday, 15 sessions). In all patients, language measures were collected before (T0) and at the end of treatment (T15). Before and after each treatment condition (real vs. sham), each participant underwent a resting-state fMRI study. Results showed that, after real stimulation, patients exhibited the greatest recovery not only in terms of better accu- racy in articulating the treated stimuli but also for untreated items on different tasks of the language test. Moreover, although after the sham condition connectivity changes were confined to the right brain hemisphere, real stimulation yielded to stronger func- tional connectivity increase in the left hemisphere. In conclusion, our data provide converging evidence from behavioral and func- tional imaging data that bilateral tDCS determines functional connectivity changes within the lesioned hemisphere, enhancing the language recovery process in stroke patients.