Table 2.
tDCS studies on language functions in patients with aphasia
| Studies on aphasic patients | Subjects | Age (mean±SD years) | Education years |
Time post stroke in months | Type of aphasia | Polarity | Electrode size (cm) | Stimulated areas | Reference electrode | Control areas | Intensity/duration | Task | Online/offline | Concomitant speech rehabilitation | Effects | Follow-up |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Frontal tDCS | ||||||||||||||||
| Monti et al52 | 8 chronic patients (4 men) | 60.37±11.99 | ≥5 | 47.13±22.89 | 4 Global 4 Broca's |
A/C/S | 5×7 | Left frontotemporal cortex | Right shoulder | Left occipital cortex | 2 mA, 10 min/single session | Picture naming | Offline | No | Cathodal tDCS improves accuracy | No follow-up |
| Hesse et al54 | 10 (5 with aphasia) sub-acute patients (3 men) | 63.3±DNR | DNR | 1–2 | 3 Global 2 Wernike's |
A | 5×7 | Left motor cortex | Contralateral supraorbital area | Right motor cortex | 1.5 mA, 7 min/30 sessions | Aachener aphasia test | Online | Yes | Anodal tDCS improves performance testing for 4 out of 5 aphasics | No follow-up |
| Baker et al55 | 10 chronic patients (5 men) | 65.50±11.44 | ≥12 | 64.60±68.42 | 6 Anomic 4 Broca's (plus AOS in 5) |
A/S | 5×5 | Left frontal cortex | Right shoulder | No | 1 mA, 20 min/5 sessions | Picture naming | Online | Yes | Anodal tDCS increases accuracy | 1 week post-treatment (the effect persisted for 1 week after treatment) |
| Marangolo et al56 | 3 chronic patients (2 men) | 66±2.65 | ≥13 | 22.33±22.67 | Non-fluent plus AOS | A/S | 5×7 | Left inferior frontal cortex | Contralateral supraorbital area | No | 1 mA, 20 min/5 sessions | Syllables, words repetition | Online (20 min) | Yes | tDCS 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 al57 | 10 chronic patients (8 men) | 61.9±2.7 | ≥9 | 52.4±21.9 | 3 Global 4 Broca's 2 Anomic 1 Transcortical |
C/S | 5×5 | Right inferior frontal gyrus | Contralateral supraorbital area | No | 2 mA, 20 min/5 sessions | Picture naming | Online | Yes | Cathodal tDCS increases accuracy 1 h following the last session | No follow-up |
| Vines et al58 | 6 chronic patients (6 men) | 55.67±16.16 | DNR | 54.17±38.03 | Broca's | A/S | 4×4 (6×5 reference) | Right inferior frontal gyrus | Contralateral supraorbital area | No | 1.2 mA, 20 min/3 sessions | Automatic speech, picture description, picture naming | Online (20 min) | Yes | Anodal tDCS improves fluency of speech | No follow-up |
| Jung et al59 | 37 sub-acute and chronic patients (26 men) | 62.4±12.9 | DNR | 27 patients≤3 10 patients>3 |
10 Fluent 26 Non fluent (not specify) |
C | 6×6 | Right inferior frontal gyrus | Contralateral supraorbital area | No | 1 mA, 30 min/10 sessions | Korean Western version of Western aphasia battery | Offline | Yes | Cathodal tDCS improves the aphasia quotient | No follow-up |
| Temporal tDCS | ||||||||||||||||
| Fiori et al49 | 3 chronic patients (3 men) | 61.33±14.84 | ≥13 | 44±25.24 | Non fluent (1 mild, 1 moderate, 1 severe) | A/S | 5×7 | Left posterior perisylvian area | Contralateral fronto-polar cortex | No | 1 mA, 20 min/5 sessions | Picture naming | Online | Yes | Anodal tDCS increases accuracy | 1 and 3 weeks post-treatment (the effect persists for 3 weeks after treatment) |
| Fridriksson et al60 | 8 chronic patients (DNR) | 68.13±10.40 | DNR | 58.38±44.60 | Fluent (anomic) | A/S | DNR | Left posterior cortex | Contralateral forehead | No | 1 mA, 20 min/5 sessions | Picture naming | Online | Yes | Anodal tDCS reduces reaction time | 3 weeks post-treatment (the effect persists for 3 weeks after treatment) |
| You et al61 | 21 subacute patients (12 men) | 66.57±10.76 | ≥6 | about 1 (25.71±7.07 days) | Global | A/C/S | 5×7 | A and S: left superior temporal gyrus C: right superior temporal gyrus |
Contralateral supraorbital area | No | 2 mA, 30 min/10 sessions (5 times/week for 2 weeks) | Auditory verbal comprehension | Offline | Yes | Cathodal tDCS improves auditory verbal comprehension | No follow-up |
| Floel et al62 | 12 chronic patients (7 men) | 52.25±8.75 | ≥5 | 84.17±65.35 | 1 Global 7 Broca's 2 Amnestic 1 Wernicke's 1 Not classified |
A/C/S | 5×7 (10×10 reference) | Right temporoparietal junction | Contralateral supraorbital area | No | 1 mA, 20 min/3 sessions | Picture naming | Online (first 20 min of treatment) | Yes | Anodal tDCS increases accuracy | 2 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.