Table 3.
Partial parameters, paradigm and results of tES effects in syllables classification and right ear advantage.
| Reference | Sample Size | Stimulation Types | Stimulation Position and Electrode Size | Reference Electrode Position and Size | Stimulation Parameters | The Number of Stimulation Sessions | EEG Recording Time | Auditory Paradigm | CV Syllables | Results |
|---|---|---|---|---|---|---|---|---|---|---|
| Heimrath et al., 2016 [84] | 13 | tDCS: anodal/cathodal/sham | Simultaneous T7 and T8, 25 cm2 | Cz 50 cm2 |
1.5 mA for 22 min. | Three stimulation sessions | Record EEG during CV-task II. Unspecified time. | Phoneme categorization task (CV-task I, II) | I: /da/ or /ta/ II: /ba/, /da/, /ga/ or /pa/, /ta/, /ka/ |
Cathodal tDCS improved the speech classification ability of CV-syllables in a VOT continuum After the anodal tDCS, the amplitude of the P50 component of all syllables increased |
| Rufener et al., 2016a [87] | Group 1: n = 21 Group 2: n = 17 |
Group 1: 6 Hz-tACS/40 Hz-tACS Group 2: no stimulation |
Simultaneous T7 and T8, 35 cm2 | Unspecified | 1.0 mA for 18 min | Two stimulation sessions | Unspecified | Phoneme categorization task (CV-task). | /da/ or /ta/ | Application of 40 Hz-tACS selectively reduced the repetition-induced improvement of phoneme categorization abilities |
| Rufener et al., 2016b [89] | Young subjects: n = 25 Older subjects: n = 20 | 6 Hz-tACS/40 Hz-tACS | Simultaneous T7 and T8, 35 cm2 | Unspecified | 1.0 mA for 8 min | Two stimulation sessions | Unspecified | Phoneme categorization task (CV-task). | /da/ or /ta/ | 40-Hz tACS on the bilateral auditory cortex, it was diminished task accuracy in young adults, older adults improved the accuracy of phonetic categorization |
| Jan et al., 2019 [94] | 26 | 40 Hz-HD-tACS/sham | Bilateral AC eight Ag/AgCl electrodes 12 mm diameter | Unspecified | 1.0 mA for 20 min | Two stimulation sessions | 5 min before and after stimulation; | Phoneme categorization task (CV-task) | Distinguish between /ba/, /da/, /ga/, /pa/, /ta/, /ka/ | The 180° tACS during DL at group level did not affect the right ear advantage The phase asymme-tries inherent in the sham-tACS process determined the directionality of behavioral modulations |
| Prete et al., 2018 [97] | Group 1: n = 50 Group 2: n = 24 |
Group 1: bilateral HF-tRNS and sham Group 2: unilateral HF-tRNS and sham |
Group 1: Simultaneous T3 and T4. 5 × 9.5 cm2 and 5 × 5 cm2 Group 2: T3, T4. 5 × 5 cm2 |
Group 1: unspecified Group 2: contralateral shoulder 5 × 9.5 cm2 | 1.5 mA for 20 min | Two stimulation sessions | Unspecified | Dichotic pairs of CV syllables | Pairs /ba/, /da/, /ga/, /pa/, /ta/, /ka/ | The right ear advantage during sham-stimulation and HF-tRNS The HF-tRNS of the bilateral AC was significantly enhanced the right ear advantage effect compared with the sham stimulation |