Table 1

tDCS studies on language functions in healthy individuals

Studies on healthy subjectsSubjectsAge mean±SD yearsEducation yearsPolarityElectrode size (cm)Stimulated areasReference electrodeControl areasIntensity/durationTaskOnline/offlineEffectsFollow-up
Frontal tDCS
 Iyer et al39103 (47 men)37.5±12.9≥12A/C/S5×5Left dorsolateral prefrontal cortexContralateral supraorbital areaNo1 and 2 mA/20 minVerbal fluency (phonemic cue)OfflineAnodal tDCS (2 mA) improves verbal fluencyNo follow-up
 Fertonani et al4112 (4 men)24.1±3.7DNRA/C/S5×7Left dorsolateral prefrontal cortexRight shoulderNo2 mA/8 and 10 minPicture namingOfflineAnodal tDCS reduces latency of responseNo follow-up
12 controls (6 men)21.8±1
 De Vries et al4244 (21 men) 6 excluded22.6±2.1>15A/S5×7Left inferior frontal gyrusContralateral supraorbital areaRight inferior frontal gyrus1 mA/20 minArtificial grammar learning and grammatical decisionOnlineLeft anodal tDCS improves the overall performance in the task of grammatical decisionNo follow-up
10 controls (5 men)23.7±2.4
 Liuzzi et al4330 (12 men)24.97±0.56>12A/C/S5×5Left motor cortexContralateral supraorbital areaLeft dorsolateral prefrontal cortex1 mA/20 minAction/objects word learning paradigmOfflineCathodal tDCS on left motor cortex reduces success rates in action words vocabulary7, 14, 28 days after tDCS
27 controls (A) (12 men)
6 controls (B) (3 men)
 Cattaneo et al4410 (4 men)23.6±3.2>12A/S5×7Left inferior frontal gyrusContralateral supraorbital areaRight inferior frontal gyrus2 mA/20 minVerbal fluency (phonemic and semantic cue)OfflineLeft tDCS improves verbal fluencyNo follow-up
8 controls (3 men)23.8±123.5
 Holland et al4510 (3 men)69±DNRDNRA/S5×7Left inferior frontal cortexContralateral frontopolar cortexNo2 mA/20 minPicture namingOnline and during fMRI studyAnodal tDCS has significant behavioural and regionally specific neural facilitation effectNo follow-up
 Wirth et al4620 (10 men)23.5±3.7>12A/S5×7Left dorsolateral prefrontal cortexRight shoulderNo1.5 mA/30 minSemantic blocking paradigm and picture namingOnline/offline (EEG)Anodal tDCS is capable of enhancing neural processes during and after applicationNo follow-up
Temporal tDCS
 Sparing et al4715 (10 men)26.9±3.7DNRA/C/S5×7Left posterior perisylvian areaVertexRight posterior perisylvian area2 mA/7 minPicture namingOffline/onlineLeft anodal tDCS reduces latency of response5/10 min after the end of tDCS
 Floel et al4819 (10 men)25.36±2.7DNRA/C/S5×7Left posterior perisylvian areaContralateral supraorbital areaNo1 mA/20 minVerbal learningOnlineAnodal tDCS facilitates learning speed and accuracyNo follow-up
 Fiori et al4910 (7 men)55±7.9>12A/S5×7Left posterior perisylvian areaContralateral fronto-polar cortexRight occipitoparietal area1 mA/20 minAssociative verbal learningOnlinetDCS on left posterior perisylvian area reduces naming response latencyNo follow-up
 Ross et al5115 (4 men)25.6±DNRDNRA/S5×7Left anterior temporal lobeContralateral cheekboneRight anterior temporal lobe1.5 mA/15 minPeople and landmark namingOnlineRight tDCS increases naming performance for famous peopleNo follow-up
  • A, anodal tDCS; 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.