Table 1.

Clinical Studies of Transcranial Direct Current Stimulation and Aphasia

Study authors and design	Subjects	tDCS polarity	Targeted hemisphere and electrode location	tDCS procedures per condition or per arm	Concurrent Behavioral treatment	Results
Monti et al, 200818 Crossover study; 4 subjects received anodal/sham conditions and 4 subjects received cathodal/sham conditions	N=8 Chronic Nonfluent aphasia (4 global, 4 Broca’s).	Anodal/sham Cathodal/sham	Left Fronto-temporal area	Single session 10 minutes at 2 mA.	None	Significantly improved naming accuracy with cathodal stimulation
Fiori et al, 201026 Crossover study with 2 conditions	N=3 Chronic Nonfluent aphasia classified as mild, moderate and severe.	Anodal/sham	Left Wernicke’s area.	5 Consecutive Daily sessions 20 minutes at 1mA	Associative picture naming training of 2 different word lists	Improved naming accuracy in both conditions, but greater improvement in the anodic versus sham condition.
Baker et al, 201024 Crossover study with 2 conditions	N=10 Chronic 6 fluent and 4 nonfluent aphasia	Anodal/sham	Left Frontal cortex	5 Consecutive Daily sessions 20 minutes at 1mA.	Self-administered Computerized Anomia Treatment consisting of spoken word picture matching	Significantly improved naming of treated items after anodal tDCS vs sham tDCS.
Fridiriksson et al, 201127 Crossover study with 2 conditions	N=8 Chronic Fluent aphasia with posterior cortical or subcortical lesions.	Anodal/sham	Left Posterior cortex	5 Consecutive Daily sessions 20 minutes at 1 mA.	Self-administered Computerized Anomia Treatment consisting of spoken word-picture matching	Greater reduction of RT for naming trained nouns after anodal tDCS vs sham tDCS on immediate post-testing and at 3 weeks follow-up.
Kang et al, 201121 Crossover study with 2 conditions	N=10 Chronic 3 global, 4 Broca’s, 1 transcortical motor, 2 anomic.	Cathodal/sham	Right Broca’s homologue area.	5 Consecutive Daily sessions 20 minutes at 2 mA.	Word-retrieval Training provided by SLP	Improved response accuracy of picture naming relative to baseline with cathodal tDCS; sham stimulation had little effect.
You et al, 201120 RCT with 3 arms	N= 21 Subacute (TPO: 16 – 38 days) Global aphasia.	Anodal Cathodal Sham	Both Left and Right (this RCT had three different study arms) Anodal tDCS to L superior temporal gyrus Cathodal tDCS to R superior temporal gyrus Sham tDCS to L superior temporal gyrus,	10 Consecutive sessions, 5 times a week for 2 weeks 30 minutes at 2 mA	“Conventional speech-language therapy”	Cathodal tDCS to right superior temporal area showed significantly greater improvements in auditory verbal comprehension than other arms.
Marangola et al, 201125 Crossover study with 2 conditions	N=3 Chronic Nonfluent aphasia with severe apraxia of speech.	Anodal/sham	Left Inferior frontal gyrus	5 Consecutive Daily sessions 20 minutes at 1 mA	Repetition of syllables and words.	Significant effect of training i.e. improvement in both anodal and sham conditions. Retention of achieved improvement only for the anodal condition.
Vines et al, 201123 Crossover study with 2 conditions	N=6 Chronic Moderate - severe nonfluent Broca’s aphasia	Anodal/sham	Right Posterior inferior frontal gyrus	3 Consecutive Daily sessions 20 minutes at 1.2mA	Melodic Intonation Therapy	Significantly greater improvement in verbal fluency with anodal tDCS than sham tDCS. condition.
Floel et al, 201122 Crossover study with 3 conditions	N=12 Chronic 7 Brocas, 1 Wernickes, 2 amnestic, 1 global and 1 not classified	Anodal, cathodal and sham	Right Temporoparietal cortex	Two times each day for 3 days 20 minutes at 1 mA	Computer assisted naming therapy - 1 set of 15 objects trained in each condition 2 hours per day; the first 20 minutes of each hour was concurrent with tDCS	Main effect of stimulation with greatest improvement on anodal tDCS. Cathodal tDCS showed greater gains compared to sham immediately after treatment but effect not maintainedat follow-up.

L = left; RT = response time; R = right; RCT = randomized controlled trial; SLP = speech-language pathologist; TPO = time post onset.