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. 2020 Aug 8;10(8):531. doi: 10.3390/brainsci10080531

Table 2.

Partial parameters and results of auditory process studies.

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 Results
Ladeira, et al., 2011 [61] 11 tDCS: anodal/cathodal/sham Simultaneous
T3 and T4,
35 cm2
Contralateral deltoid muscle 35 cm2 2.0 mA for 10 min Three stimulation sessions unspecified Random gap detection test Anodal tDCS enhanced temporal resolution and cathodal diminished temporal resolution
Heimrath, et al., 2014 [62] 15 tDCS: anodal/sham T7, T8, 25 cm2 Contralateral C4, C3, 50 cm2 1.5 mA for 13 min Two stimulation sessions unspecified Between channel gap detection task Anodal tDCS over the left auditory cortex diminished temporal resolution
Baltus, et al., 2018 [65] 26 IGF ± 4 Hz tACS Left hemispheric: FC5 and TP7/P7
Right hemispheric: FC6 and TP8/P8
Each hemispheric two round electrodes (2.5 cm diameter)
unspecified 1.0 mA for 7 min Each participant had one stimulation session within two days Day 1: 40 min in the IGF estimation.
Day 2: 1.5 min in the aftereffect estimation.
Between channel gap detection task Participants in Group A (tACS frequency above IGF) performed significantly better during tACS compared to participants in Group B (tACS frequency below IGF)
Both groups had significant relative changes in the amplitude of ASSR
Baltus, et al., 2020 [66] 16 IGF + 3 Hz tACS
or IGF − 4 Hz tACS
Left hemispheric: FC5 and TP7/P7
Right hemispheric: FC4 and TP8/P8
Each hemispheric two round electrodes (2.5 cm diameter)
unspecified 1.0 mA for 8.5 ± 1.7 min Each participant had two stimulation sessions within two days Day 1: 20 min in the IGF estimation. Between channel gap detection task The IGF was significantly related to the gap detection performance under the condition that the baseline and tACS frequency were higher than IGF 3 Hz
Under the condition that the tACS frequency was higher than IGF 3 Hz, tACS could modulated gap detection performance
Rufener, et al., 2017a [67] 20 HF-tRNS (100–640 Hz)/sham Over T7 and T8 35 cm2 unspecified 1.5 mA for 40 min Two stimulation sessions. Stimulation twice in each session. Record EEG during gap task and pitch task. Unspecified time. Between channel gap detection task and pitch discrimination task. Auditory tRNS only increased the detection rate in the temporal domain, no such effect on the discrimination of spectral features
The facilitation effect of tRNS was limited to the processing of stimuli near the threshold
Rufener, et al., 2017b [68] 18 tRNS/sham unspecified frequency LAC, RAC, BAC unspecified size unspecified 1.5 mA for 30 min Four stimulation sessions. tRNS simultaneous EEG
About 30 min
Between channel gap detection task and pitch discrimination task. The application of tRNS on LAC and BAC was related to task performance
LAC had functional relevance when dealing with temporal features, and this effect was modulated by the the inter-tone interval between the tone triplets
Lewald 2016 [70] 74 tDCS: anodal and cathodal/sham (1) superior temporal gyrus (STG, n = 24)
(2) inferior parietal lobule (IPL, n = 28)
(3) somatosensory-motor cortex (SMC, n = 22).
Two round electrodes (diameter 21 mm, 3.5 cm2)
unspecified 0.4 mA for 12 min Each participant had one stimulation session at a different stimulation site unspecified Simulated “cocktail-party” situation The tDCS over superior temporal gyrus could enhance the accuracy of target localization in left hemispace
TDCS over IPL and off-target active stimulation over SMC found no significant effects
Lewald 2019 [71] 24 tDCS: anodal/sham Midpoint between C5 and T7 locations and C6 and T8 locations 35 cm2 over the contralateral shoulders 7 × 14 cm 1.0 mA for 32 min Two stimulation sessions unspecified Simulated “cocktail-party” situation TDCS over the region of posterior STG, significantly improved the performance in localizing a target speaker
Compared with sham tDCS, the average increase in correct responses by 3.7% after active tDCS
Hanenberg, et al., 2019 [72] 39 tDCS: anodal/cathodal/sham Midpoint between C6 and T8 35 cm2 over the contralateral shoulder(left) 7 × 14 cm 1.0 mA for 16 min Three stimulation sessions. Whole session about 91 min; Simulated “cocktail-party” situation The amplitude of the response of the N2 component on the contralateral (left) increased significantly within 15 min after tDCS
At the same point in time, the posterior parietal cortex (PPC) electrical activity reduced on the same side (right)
Malte, et al., 2018 [78] 20 10 Hz tACS and sham or 47 Hz tACS and sham FC5 and TP7 Round electrodes of 3 cm diameter unspecified 1.0 mA for 25 min Each participant received two sessions, each session included one sham and one real tACS unspecified Dichotic listening task Unihemispheric α-tACS relatively reduced the recall of targets contralateral to stimulation, increased recall of ipsilateral targets
Contrary to α-tACS, γ-tACS relatively increased the recall of targets contralateral to stimulation, decreased recall of ipsilateral targets
Deng, et al., 2019 [79] 38 10 Hz HD-tACS/6 Hz HD-tACS/sham P2 ring electrode unspecified size CP2, P4, Pz, PO4 ring electrode unspecified size 1.5 mA for 20 min Each participant received one sham and one HD-tACS unspecified Selective auditory attention task RIPS’ α-HD-tACS disrupts auditory spatial attention for leftward
No effect on performance in the myriad control conditions (i.e., gender, continuous/switching experiment, theta stimulation)
Rufener, et al., 2018 [82] 20 HF-tRNS (100–640 Hz)/sham F3 25 cm2 right shoulder 35 cm2 1.5 mA for 30 min executed twice per session Two stimulation sessions. tRNS simultaneous EEG
About 60 min
Oddball paradigm (target tone recognition) TRNS regulates the excitability of the left DLPFC
TRNS reduced the subject’s response time to identify the target sound, and fastened up the latency of the P3 component