Table 1.

Methodological characteristics of included studies

Study	Design	NiBS	SLT	Sessions	Stimulation parameters	Stimulation target	Linguistic test(s)	Post-treatment evaluation	Follow-up(s) evaluation(s)
Cotelli et al. (2014)	Parallel	tDCS	Picture-naming training	10 daily sessions(× 2 weeks)	5 × 5 ${\text{cm}}^2$ electrodes; 2 mA, 20 min	Anode: 8 cm frontally and 6 cm laterally with respect to Cz Cathode: right arm	Picture naming, AATg, grammar comprehension (BADAh), phonemic fluency, semantic fluency	Immediate post-treatment	12 weeks from baseline
McConathey et al. (2017)	Crossover	tDCS	None (narrative task only)	10 daily sessions (× 2 weeks)	5 × 5 ${\text{cm}}^2$ electrodes, 1.5 mA, 20 min	Anode: F7 Cathode: O1	Sentence repetition, grammar comprehension (TROGi), semantic fluency, picture naming (BNTj), semantic associations (PPTk)	Immediate post-treatment	6 and 12 weeks post- treatment
Roncero et al. (2017)	Crossover	tDCS	Picture-naming training	10 daily sessions (× 3 weeks)	5 × 7 ${\text{cm}}^2$ electrodes, 2 mA, 30 min	Anode: TP9 Cathode: right fronto-orbital area	Picture naming	Immediate post-treatment	2 weeks post-treatment
Ferrucci et al. (2018)	Crossover	tDCS	None	5 daily sessions (× 1 week)	5 × 7 ${\text{cm}}^2$ electrodes, 2 mA, 20 min	Anode: F7 and F8 Cathode: right deltoid	Phonemic fluency, picture naming	Immediate post-treatment	1 and 4 weeks post-treatment
Hosseini et al. (2019)	Crossover	tDCS	None (narrative task only)	10 daily sessions (× 2 weeks)	5 × 5 ${\text{cm}}^2$ electrodes, 1.5 mA, 20 min	Anode: F7 Cathode: O1	Semantic fluency, grammar comprehension (TROG), semantic associations (PPT), picture naming (BNT)	Immediate post-treatment	6 and 12 weeks post-treatment
Benussi et al. (2020)	Parallel	tDCS	None	10 daily sessions (× 2 weeks)	5 × 7 ${\text{cm}}^2$ electrodes, 2 mA, 20 min	Anode: F3 Cathode: right deltoid	Phonemic fluency, semantic fluency	Immediate post-treatment	3 and 6 months from baseline
de Aguiar et al., (2020a, 2020b)	Parallel	tDCS	Picture-naming training	12 daily sessions on average (± 2) (× 3 weeks)	5 × 5 ${\text{cm}}^2$ electrodes, 2 mA, 20 min	Anode: F7 Cathode: right cheek	Written picture naming	Immediate post-treatment	2 weeks and 2 months post-treatment
Pytel et al. (2021)	Mixed	rTMS	None	15 daily sessions (× 3 weeks)	20 Hz, 20-s inter-train, 1500 pulses, 100% RMTa	Personalized target: LIFGb (9 patients), LSFGc (3 patients), LDLPFCd (6 patients), RSFGe (1 patient), LATLf (1 patient)	Story description, picture naming, story reading, repetition	Within the first 2 weeks post-treatment	None
Nissim et al. (2022)	Crossover	tDCS	Constraint-induced language therapy (CILT)	10 daily sessions (× 2 weeks)	1-cm diameter round electrodes, 1.5 mA, 20 min	Anode: FT7 Cathodes: F7, T7, FC5, FT9	Western aphasia battery-revised (WAB-R)	Immediate post-treatment	6 weeks post-treatment
Wang et al. (2022)	Parallel	tDCS	Picture-naming training	Approximately 12 daily sessions (× 3 weeks)	5 × 5 ${\text{cm}}^2$ electrodes, 2 mA, 20 min	Anode: F7 Cathode: right cheek	Semantic and phonemic fluency	Immediate post-treatment	2 weeks and 2 months post-treatment
Borrego-Ecijia et al. (2023)	Crossover	tDCS	Unspecified SLT type	10 daily sessions (× 2 weeks)	1-cm radius round electrodes, max 4 mA, 26 min	Anodes: F7, FC1, FC5, P7 Cathodes: PO8, C1, FPZ	Phonemic fluency, semantic fluency, picture naming, single-word comprehension, semantic associations (Camel and Cactus test, PPT), reading	Immediate post-treatment	1 and 3 months post-treatment
Huang et al. (2023)	Parallel	rTMS	None	20 daily sessions (× 4 weeks)	10 Hz, 2-s inter-train, 1000 pulses, 120% RMT	LDLPFC	Picture naming, WAB	1-month post-treatment	3 and 6 months post-treatment

^aRMT resting motor threshold

^bLIFG left inferior frontal gyrus

^cLSFG left superior frontal gyrus

^dLDLPFC left dorsolateral prefrontal cortex

^eRSFG right superior frontal gyrus

^fLATL left anterior temporal lobe

^gAAT Aachener Aphasie Test

^hBADA battery for the analysis of the aphasic deficit

ⁱTROG Penn-Test for reception of grammar

^jBNT Boston Naming Test

^kPPT Pyramids and Palm Trees Test