Table 2

tDCS studies on language functions in patients with aphasia

Studies on aphasic patientsSubjectsAge (mean±SD years)Education
years
Time post stroke in monthsType of aphasiaPolarityElectrode size (cm)Stimulated areasReference electrodeControl areasIntensity/durationTaskOnline/offlineConcomitant speech rehabilitationEffectsFollow-up
Frontal tDCS
 Monti et al528 chronic patients (4 men)60.37±11.99≥547.13±22.894 Global
4 Broca's
A/C/S5×7Left frontotemporal cortexRight shoulderLeft occipital cortex2 mA, 10 min/single sessionPicture namingOfflineNoCathodal tDCS improves accuracyNo follow-up
 Hesse et al5410 (5 with aphasia) sub-acute patients (3 men)63.3±DNRDNR1–23 Global
2 Wernike's
A5×7Left motor cortexContralateral supraorbital areaRight motor cortex1.5 mA, 7 min/30 sessionsAachener aphasia testOnlineYesAnodal tDCS improves performance testing for 4 out of 5 aphasicsNo follow-up
 Baker et al5510 chronic patients (5 men)65.50±11.44≥1264.60±68.426 Anomic
4 Broca's (plus AOS in 5)
A/S5×5Left frontal cortexRight shoulderNo1 mA, 20 min/5 sessionsPicture namingOnlineYesAnodal tDCS increases accuracy1 week post-treatment (the effect persisted for 1 week after treatment)
 Marangolo et al563 chronic patients (2 men)66±2.65≥1322.33±22.67Non-fluent plus AOSA/S5×7Left inferior frontal cortexContralateral supraorbital areaNo1 mA, 20 min/5 sessionsSyllables, words repetitionOnline (20 min)YestDCS increases accuracy both in sham and anodal condition, but the effect persists only after anodal condition.1 week, 1 month and 2 months post-treatment (generalisation of the recovery at language examination tests persists for 2 months after treatment)
 Kang et al5710 chronic patients (8 men)61.9±2.7≥952.4±21.93 Global
4 Broca's
2 Anomic
1 Transcortical
C/S5×5Right inferior frontal gyrusContralateral supraorbital areaNo2 mA, 20 min/5 sessionsPicture namingOnlineYesCathodal tDCS increases accuracy 1 h following the last sessionNo follow-up
 Vines et al586 chronic patients (6 men)55.67±16.16DNR54.17±38.03Broca'sA/S4×4 (6×5 reference)Right inferior frontal gyrusContralateral supraorbital areaNo1.2 mA, 20 min/3 sessionsAutomatic speech, picture description, picture namingOnline (20 min)YesAnodal tDCS improves fluency of speechNo follow-up
 Jung et al5937 sub-acute and chronic patients (26 men)62.4±12.9DNR27 patients≤3
10 patients>3
10 Fluent
26 Non fluent
(not specify)
C6×6Right inferior frontal gyrusContralateral supraorbital areaNo1 mA, 30 min/10 sessionsKorean Western version of Western aphasia batteryOfflineYesCathodal tDCS improves the aphasia quotientNo follow-up
Temporal tDCS
 Fiori et al493 chronic patients (3 men)61.33±14.84≥1344±25.24Non fluent (1 mild, 1 moderate, 1 severe)A/S5×7Left posterior perisylvian areaContralateral fronto-polar cortexNo1 mA, 20 min/5 sessionsPicture namingOnlineYesAnodal tDCS increases accuracy1 and 3 weeks post-treatment (the effect persists for 3 weeks after treatment)
 Fridriksson et al608 chronic patients (DNR)68.13±10.40DNR58.38±44.60Fluent (anomic)A/SDNRLeft posterior cortexContralateral foreheadNo1 mA, 20 min/5 sessionsPicture namingOnlineYesAnodal tDCS reduces reaction time3 weeks post-treatment (the effect persists for 3 weeks after treatment)
 You et al6121 subacute patients (12 men)66.57±10.76≥6about 1 (25.71±7.07 days)GlobalA/C/S5×7A and S: left superior temporal gyrus
C: right superior temporal gyrus
Contralateral supraorbital areaNo2 mA, 30 min/10 sessions (5 times/week for 2 weeks)Auditory verbal comprehensionOfflineYesCathodal tDCS improves auditory verbal comprehensionNo follow-up
 Floel et al6212 chronic patients (7 men)52.25±8.75≥584.17±65.351 Global
7 Broca's
2 Amnestic
1 Wernicke's
1 Not classified
A/C/S5×7 (10×10 reference)Right temporoparietal junctionContralateral supraorbital areaNo1 mA, 20 min/3 sessionsPicture namingOnline (first 20 min of treatment)YesAnodal tDCS increases accuracy2 weeks post-treatment (the effect persists for 2 weeks after treatment)
  • A, anodal tDCS; AOS, apraxia of speech; C, cathodal tDCS; DNR, data not reported; mA, milliampere; offline, the subject executes the task before and after stimulation; online, the subject executes the task during stimulation; S, sham tDCS; SD, standard deviation; tDCS, transcranial direct current stimulation.