Transcranial Direct Current Stimulation as a Tool to Induce Language Recovery in Patients with Post-Stroke Aphasia : An Overview of Studies

In recent years, possible therapeutic effects of transcranial direct current stimulation (tDCS) have been widely investigated in studies of different types of neural pathologies. Recent reviews of tDCS in patients with post-stroke aphasia did not provide coherent evidence oа its efficiency. There were no uniform protocols of stimulation, patient selection criteria were highly divergent, and the reports of treatment outcomes varied dramatically. In this review, we focus on the reported heterogeneity of tDCS effects trying to disentangle its putative underpinnings rooted in the diversity of lesion types, aphasia severity and recovery stages. Given the current theoretical models suggesting qualitatively different patterns of brain activity which accompany aphasia recovery, various physiological factors should be taken into account to choose optimal tDCS parameters. With this in mind, we assess the results of ten studies applying tDCS in post-stroke aphasia treatment, and suggest directions for further research in this rapidly developing field