Table 2.
Reported stimulation parameters in studies on acute/short-term tVNS.
| References | Device | Electrode(s) | Stimulus intensity | Pulse width | Hz | Alternating stimulation | Stimulus | Electrode placement | Stimulation length | Task | Pre-task stimulation period |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Sclocco et al. (2019) | Model S88x, Grass Instruments, Astro-Med, Inc, West Warwick, RI, USA | Custom ergonomic electrodes, Bionik Medical Devices, Bucaramanga, Colombia | eRAVANS: 1.6 ± 2.3 mA; iRAVANS: 1.7 ± 2.4 mA; GANctrl: 1.4 ± 1.1 mA |
450 μs | 25 | Gated to respiratory cycle (1 s per cycle) | Biphasic rectangular pulse trains | Left cymba concha; Left earlobe | 8 min per condition | Brainstem fMRI (no task) | None |
| Sclocco et al. (2020) | UROstim, schwa-medico GmbH, Ehringshausen, Germany | Custom ergonomic electrodes, Bionik Medical Devices, Bucaramanga, Colombia | 2 Hz: 7.18 ± 0.95 mA; 10 Hz: 6.46 ± 1.30 mA; 25 Hz: 5.93 ± 1.21 mA; 100 Hz: 5.57 ± 1.18 mA |
300 μs | 2, 10, 25, 100 | Gated to exhalation (1.5 s per respirator cycle) | Monophasic rectangular pulse trains | Left cymba concha | 8.5 min per condition | Brainstem fMRI (no task) | None |
| Borges et al. (2019) | Nemos®, Cerbomed, Erlangen, Germany | Two titanium electrodes, positioned on top of a silicon earplug | M = 2.3 mA (SD = 0.08 mA) | 200–300 μs | 25 | 30-s waves of electrical stimulation alternated by 30-s breaks | Cymba conchae of the left ear | 10 min | None | None | |
| Borges et al. (2020) | Nemos®, Cerbomed, Erlangen, Germany | Two titanium electrodes, positioned on top of a silicon earplug | M = 2.19 mA (SD = 0.93) | 200–300 μs | 25 | 30-s waves of electrical stimulation alternated by 30-s breaks | Cymba conchae of the left ear | 9–17 min, depending on the task | Modified Flanker task, Spatial Stroop task, Number Letter task, and Dimension Change Card Sorting task | 4 min before each task | |
| Leutzow et al. (2013) | Nihon Kohden MEB 9200 | Customa | 8 mA | 0.1 ms duration | 0.5 | Electrical square impulses | Right tragus | VSEP simultaneously measured before and after Total Intravenous Anesthesia (TIVA) | |||
| Schulz-Stübner and Kehl (2011) | NMS 300; Xavant Technology, Pretoria, South Africa | 6 mA | 1 | Stimulated at a frequency of 1 Hzfor 30 s and then a brief tetanic stimulus was applied |
Left interscalene groove | 30 s | |||||
| Kox et al. (2015) | Medtronic model 37022 | Stimulation catheter with eight electrodes on a circular distal loop (Achieve Medtronic model 990063-20, Medtronic, Heerlen, The Netherlands) |
2–10 V | 1 ms | 20 | Continuous | C5–C7 spinal level | 30 min | Continuous physio up to 8 h following stim onset and 2 days post; 10 min before LPS administration and assess temp/symptoms every 30 min for 8 h and 2 days post | ||
| Burger et al. (2019a) | Nemos®, Cerbomed, Erlangen, Germany | Two titanium electrodes, positioned on top of a silicon earplug | 0.5 mA | 250 μs | 25 | 30-s waves of electrical stimulation alternated by 30-s breaks | Cymba concha of left ear | Across 3 tasks, this current task is 15 min (30 min + more for other tasks) | Breathing Focus Task | 15 min | |
| Hyvärinen et al. (2015) | Tinnoff Inc. | Clip electrode | 0.5 mA | 500 μs | 25 | Biphasic rectangular pulse | Left tragus | 6 min | MEG | 1 min | |
| Sellaro et al. (2015b) | CM02, Cerbomed, Erlangen, Germany | Two titan electrodes fastened on a gel frame | 0.5 mA | 200–300 μs | 25 | Alternated between on and off periods every 30 s | Outer auditory canal of the left ear |
75 min | Flanker and CRT, mood and physio assessed 45 and 75 min post | 15 min | |
| Verkuil and Burger (2019) | Nemos®, Cerbomed, Erlangen, Germany | Two titanium electrodes, positioned on top of a silicon earplug |
0.5 mA | 250 μs | 25 | 30-s waves of electrical stimulation alternated by 30-s breaks | Cymba conchae of the left ear | Across 3 tasks + 15 min | Exogenous cuing task | 15 min to first task | |
| Jacobs et al. (2015) | TENSTem dental; Schwa-medico BV, Woudenberg, The Netherlands | Ear clip using a circular electrode of 10 mm diameter connected as an anode | 5.0 mA | 200 μs | 8 | Left external acoustic meatus on the inner side of the tragus | 17 min | Continuous physio data and retrieval task post-stim | Continuous, 17 min | ||
| Burger et al. (2018) | Nemos®, Cerbomed, Erlangen, Germany | Two titanium electrodes, positioned on top of a silicon earplug | 0.5 mA | 250 μs | 25 | 30-s waves of electrical stimulation alternated by 30-s breaks | Concha of the left outer ear | 26 min | Extinction | 12 min | |
| Finisguerra et al. (2019) | NEMOS® device (CM02 Cerbomed, Erlangen, Germany) | Two titan ear electrodes that are mounted on a gel frame |
0.5 mA | 200–300 μs | 25 | Alternated between On/Off periods of 30 s each |
Cymba conchae of the left ear | 60 min | IATS | 15–20 min | |
| Colzato et al. (2018b) | NEMOS® | 0.5 mA | 200–300 μs | 25 | Alternated between on and off periods every 30 s |
Outer auditory canal of the left ear |
50 min | Emotion Regulation Task and assessed flow at the end | 20 and 50 min | ||
| Jongkees et al. (2018) | CMO2, Cerbomed, Erlangen, Germany | Titan electrodes mounted on a gel frame | 0.5 mA | 200–300 μs | 25 | Active stimulation for 30 s, followed by a break of 30 s | Outer auditory canal of left ear | 45 min | SRT | 15 min | |
| Steenbergen et al. (2015) | CM02, Cerbomed, Erlangen, Germany | Two titan electrodes mounted on a gel frame | 0.5 mA | 200–300 μs | 25 | 30 s, followed by a break of 30 s | Outer auditory canal of left ear |
45 min | Task test phase 25 minutes into stim and HR post-stim | 25 and 45 min | |
| Sellaro et al. (2018) | NEMOS® | Two titan electrodes mounted on a gel frame | 0.5 mA | 200–300 μs | 25 | On and off periods of stimulation alternated every 30 s | Auricle with the titan electrodes placed either in contact with the concha of left ear | 35 min | Emotion regulation | 20 min | |
| Colzato et al. (2018a) | NEMOS | 0.5 mA | 200–300 μs | 25 | Alternated between on and off periods every 30 s | Concha in the left ear | 40 min | Creativity tasks and personality and HRV | 15 min | ||
| Fischer et al. (2018) | CMO2, Cerbomed, Erlangen, Germany | Two titan electrodes mounted on a gel frame | M = 1.3 mA (0.4–3.3 mA) | 200–300 μs | 25 | Continuous | Left cymba conchae |
36 min | Oddball then Simon task, physio/mood/ EEG/saliva post | Simultaneous with 2 tasks, 28 min before task of interest, 36 min | |
| Keute et al. (2019a) | Digitimer DS7 and Arduino Uno circuit board |
Medical Ag/AgCl electrodes (Ambu Neuroline3), cut to a size of 4 × 4 mm and mounted on a piece of silicone at a center-to-center | 3 mA | 200 μs | 25 | Stimulation cycle of 30 s stimulation at 25 Hz, followed by a 30 s break | Cymba conchae of the left ear; anode was placed more rostral | 40 min | 10-min online task | 30 min | |
| distance of 1 cm were used |
|||||||||||
| Laqua et al. (2014) | TNS SM 2 MF device (Schwa-Medico GmbH, Germany | Anode: silver disk EEG electrode 5 mm in diameter, Schuler Medizintechnik Freiburg, Germany Cathode: (Blue Sensor PECG electrode, Ambu, Germany) |
Intensity of stimulation was set individually to maximal but non-painful | 0.2 ms impulse duration | Changing frequency between 2 and 100 Hz | Burst-stimulation mode | Anode: bilateral cavum conchae Cathode: mastoid area of the ear |
35 min (5 min adaptation + 30 min constant) | Physio measures 15, 30, 40, and 60 min after onset | ||
| Brock et al. (2017) | GammaCore; electroCore LLC; Basking Ridge, NJ, USA | Two steel contact electrodes | (1) left cervical vagal nerve and (2) to the right cervical vagus nerve | 120 s to each site | Measured 90 min and 24 h after tVNS | ||||||
| Peng et al. (2018) | TENS200, HUATUO GmbH, Hangzhou, China | Silver plate (5 mm in diameter) and an elongated cylindrical silver stimulation electrode (8 mm in length, 3 mm in diameter) | Around 5 mA on the acupuncture points (varied individually between 4 and 8 mA) |
250 μs | 20 | Monophasic-modified rectangle impulse | Area of the acupuncture points CO10-12 and TF4b OR anterior wall of the auditory canalc | First stimulation period of 30 s and a break/baseline of 60 s. Four alternating stimulation and baseline sequences were performed in total | Simultaneous MRI | ||
| Warren et al. (2019, p. 20) | NEMOS®, Cerbomed, Germany | 0.5 mA | 200–300 μs | 25 | Alternating between on and off periods every 30 s | Cymba conchae region | 80 min | Saliva 45 min and post-tVNS, and pupilometry 20 and post-tVNS, EEG simultaneous, stimulus discrimination 20 min after tVNS onset | 20 min | ||
| Burger et al. (2016) | Nemos_, Cerbomed, Erlangen, Germany | Two titanium electrodes, positioned on top of a silicon earplug |
0.5 mA | 25 | 30-s waves of electrical stimulation alternated by 30-s breaks | Concha of the left outer ear | ~3 min (8 s*20) | During extinction | 10 min | ||
| Busch et al. (2013) | STV02, Cerbomed, Erlangen, Germany | Bipolar stimulation electrode | 0.25 and 10 mA | 250 μS | 25 | Continuous | Modified monophasic rectangle impulse | Left concha at the inner side of the tragus | 1 h | Continuous ANS, pain assessment | 20 min |
| Burger et al. (2019b) | CM02, Cerbomed, Erlangen, Germany | Two titan electrodes mounted on a gel frame | 0.5 mA | 250 μs | 25 | Active for 30 s, followed by a break of 30 s | Cymba concha of the left outer ear | 30 min | Fear generalization and extinction | 10 min | |
| Capone et al. (2015) | Twister—EBM | Two Ag–AgCl electrodes (5 mm in diameter) | 8 mA | Pulse duration = 0.3 ms | 20 | Trains lasting 30 s and repeated every 5 min for 60 min | Trains composed by 600 pulses (intra-train pulse frequency = 20 Hz; pulse duration = 0.3 ms) | Left external acoustic meatus at the inner side of the tragus | 60 min | Cortical excitabity TMS post-tVNS | 60 |
| Sclocco et al. (2017) | Ergonomically-shaped Ag/AgCl electrodes | Low and medium 0.10 ± 0.08 mA and 0.26 ± 0.15 mA | 15 ms pulse width | 25 | Duration of 1 s, delivered at 25 Hz during each exhalation phase of respiration. |
Rectangular pulses | Left ear | 2 min | Simultaneous with paced breathing and ECG | ||
| Genheimer et al. (2017) | NEMOS cerbomed GmbH (Erlangen, Germany) | 1.2 (1.1) MA | 250 μS | 25 | 30 s on and 30 s off phases | Cymba concha left ear | 60 min (20 min + 40 min during task) | During extinction and during entering office for extinction; assess reinstatement next day | 20 min | ||
| Usichenko et al. (2017b) | DoloBravo Dual Channel Neurostimulator (MTR GmbH, Germany) | Self-manufactured electrode, sized 9 × 9 × 2.1 mm; contact surfaces of each electrode, containing the silver wires wrapped in wool, were moistened with 0.9% NaCl solution |
7.6 mA (range 5.0–11.5) | Impulse duration of 200 μs | 8 | Continuous | Square impulses | Concha of the auricle bilateral |
~6 min | Simultaneous with heat pain during fMRI and threshold assessed post-tDCS | |
| Cha et al. (2016) | ES-420, Ito Co., Ltd., Tokyo, Japan |
Ball-type electrode | 2–7 mA across sites/2 days | 200 μs | 30 | Cymba, the cavum, and the outer surface of the tragus (Right and Left) | 4 min per site | N | Assessed dizziness after tVNS | ||
| Yakunina et al. (2017) | Custom-made stimulator connected with silver wires to six electrodes | 99.99% pure silver (four stimulation and two reference electrodes) |
The stimulation intensities at electrodes A, B, C, and D ranged from 0.2–1.8 mA with means ± SD of 0.77 ± 0.42, 0.81 ± 0.48, 0.91 ± 0.47, and 0.81 ± 0.38 mA, respectively |
500 μs | 25 | Monophasic rectangular impulse | 4 locations in the left ear: (A) inner surface of the tragus, (B) inferoposterior wall (cartilaginous part) of the ear canal, (C) cymba conchae, and (D) earlobe. The reference electrode for electrodes A, B, and C were placed at the outer surface of the tragus, whereas the reference electrode for electrode D (sham) was placed at the backside of the earlobe |
Each location was stimulated in two runs with 30 s of stimulation followed by 1 min of rest; this cycle was repeated four times in a run. Each subject underwent eight 6-min fMRI runs total, with up to 90 s of rest in between run | Simultaneous MRI | ||
| Clancy et al. (2014) | Transcutaneous Electrical Nerve Stimulation (TENS) device (V-TENS Plus, Body Clock Health Care Ltd, UK) |
Modified surface electrodes | Level of sensory threshold (10–50 mA) | 200 μs | 30 | Continuous | Inner and outer surface of the tragus of the ear | 15 min | Simultaneous physio and over 15 min following recording | ||
| Antonino et al. (2017) | (TENS) device consisted of a small stimulation unit (V-TENS Plus, Body | Surface electrodes bilaterally placed | 45 ± 1 mA | 200 μs | 30 | Continuous | Inner and outer surface of the tragus | 15 min | Simultaneous physio and during 10 min period post-tVNS | ||
| Clock Health Care Ltd, UK) | |||||||||||
| Lamb et al. (2017) | Ag/AgCl disk electrode | 80% of comfort threshold of 5.6 mA (range 3–11.3 mA) | 100 μS | 20 | Alternating polarity pulse | Left external auditory meatus and the posterior face of the left tragus | Startle blink and ANS tests | Simultaneous | |||
| Lerman et al. (2016) | Two stainless steel contact surfaces and conductive gel | M intensity ranged from 21.3 to 22.59 across the 6 stimulations | 25 | 5-kHz sine wave series that occurred for 1 ms and repeated every 40 ms |
Under the angle of the mandible, lateral to the trachea and medial to the sternocleidomastoid (right then left ear 3 times each) |
2 min (90 s with 30 s ramp up | N | Blood draw 90 min after first stim and next day | |||
| Badran et al. (2018b) | Digitimer DS7a | Custom developed round, unipolar stimulation Ag/AgCl electrodes 1 cm in diameter, affixed to the 3D-printed clamps using cyanoacrylate | Mean ± SD: 3.14 ± 0.99 mA | 500 μs | 25 | Three stimulation “on” periods were modeled (onset times: 30, 150, 270 s; duration 60 s) | Monophasic square waves | Left tragus | 5.5 min (270 s onset time + 60 s) | Simultaneous MRI | |
| Frøkjaer et al. (2016) | NEMOS, Cerbomed, Erlangen, Germany | Bipolar stimulation electrode | 0.1–10 mA readjusted throughout experiment; mean ranged from 1.07 mA to 1.46 across time points | 250 μs | 30 | Left concha | 60 min | Cardiac derived parameters obtained at baseline and after 10, 20, and 30 min of tVNS; Quantitative sensory testing assessed at baseline and after 10 and 25 min of tVNS; Conditioned pain modulation Assessment was performed after 40 min of tVNS; Drink test for assessment of | 15 min (deep breathing) | ||
| gastroduodenal motility performed after 50 min of tVNS | |||||||||||
| Garcia et al. (2017) | S88X GRASS stimulator, Astro-Med, Inc, West Warwick, RI | 8 mm diameter, Astro-Med, Inc, West Warwick, RI | Exhalatory-gated taVNS (eRAVANS) mean ± SD: 1.22 ± 1.33 mA Inhalatory-gated taVNS (iRAVANS) mean ± SD: 0.85 ± 1.07 mA |
450 μs | 30 | Pulse train duration of 0.5 s gated, with 0.5-s delay, after peak inhalation (i.e., during exhalation, for eRAVANS) or after peak exhalation (i.e. during inhalation, for iRAVANS) | Biphasic rectangular pulses | Auricle of the left ear [(1) the cymba concha and (2) the slope between the antihelix and cavum concha] | 360 s | Airpuff stimulation was applied over the right supraorbital region of the forehead in fMRI scans pre- and post-stimulation | |
| Rufener et al. (2018) | NEMOS tVNS device (Cerbomed, Erlangen, Germany) | 0.5 mA | 250 μs | 25 | Alternating on/off phases of 30 s | Concha cymbae of the left ear |
100.5 min | Oddball task | 90 min | ||
| Burger et al. (2017) | NEMOS® stimulator unit (Cerbomed, Erlangen, Germany) | 0.5 mA | 250 μs | 25 | Each CS was presented for 30 s, followed by a 40 s inter trial interval (ITI). Stimulation (sham) with the tVNS device occurred concurrently with each CS for 30 s |
Monophasic square wave pulses | Concha of the left ear | Twenty unreinforced presentations of the CS+ and CS– | Fear extinction | Simultaneous with extinction task; Assessed retention 24 h later | |
| Stavrakis et al. (2015) | Grass S88 stimulator | Flat metal clip | 50% below threshold for slowing sinus rate of 39.8 ± 25.7 V | 1-ms duration | 20 | Continuous | Square wave | Right ear, tragus cathode, earlobe anode | 1 h | Post-tVNS blood draw and atrial fibrillation induction | |
| Yu et al. (2017) | S20, Jinjiang, Chengdu City, China |
50% below threshold for slowing sinus rate of 5.8 ± 3.1 mA | 1-ms duration | 20 | Duty cycle of 5 s on and 5 s off |
Right Tragus | 155 ± 6 min | Holter Recording | 24 h recording post tDCS and daily follow ups for 1 week | ||
| Paleczny et al. (2019) | IMER Systems, Wroclaw, Poland |
Custom-made electrode | Mean amplitude= 722 ± 92 μA | 1,000 μs/phase | 25 | Continuous or Synchronizing the stimulation with the inspiratory or expiratory phase | Rectangular, biphasic, symmetrical pulses (1,000 μs/phase, interphase interval 30 μs) | Medial of the tragus at the entry of the acoustic meatus | 2 min each | Simultaneous physio | |
| Fallgatter et al. (2003) | Two conventional bipolar electrode wires were soldered to single-sided copper claddings upon epoxy resin; At the output side two very flexible fine copper stranded wires ~10 cm in length and with a diameter of 0.05 mm, cut from a radio coil, were soldered to the copper claddings |
Epoxy resin (dimension about 1 × 1 cm) | 8 mA | 0.1 ms duration | Interstimulus interval of 2 s | Electrical square impulses | Cathode of this bipolar stimulation electrode was placed at the inner side of the tragus at the outer ventral edge of the meatus acusticus externus. The anode was also placed at the inner side of the tragus 5 mm more distal. Alternative stimulation sites at the right ear outside the innervation of the auricular branch were tested in the single subject (lobulus auriculae, the scapha, the crus antihelices superior and the top of the helix). The distance between cathode and anode was always kept at 5 mm |
Simultaneous VSEP | |||
| Polak et al. (2009) | Two conventional bipolar electrode wires soldered to single-sided copper claddings at the input side. At the output side, two very flexible fine copper stranded wires were soldered to the copper claddings. The other end of these wires was fixed to the skin with GRASS paste |
Stimulation electrode was a piece of epoxy resin with two conventional bipolar electrode wires soldered to single-sided copper claddings at the input side |
5, 8, and 10 mA in randomized sequence |
0.1 ms duration | Interstimulus interval of 2 s | Electrical square impulses | Cathode of the bipolar stimulation electrode was placed at the inner side of the tragus at the outer ventral edge of the internal auditory meatus, the anode 5 mm away right and left ear | Simultaneous VSEP | |||
| Lewine et al. (2019) | gammaCore device | 12–20 V | 25 | Two 120-s long bursts of stimulation applied over a 5 min period |
5 kHz sine-wave stimulus for 1 ms |
Left carotid sheath | 5 min | EEG | 15 min after active or sham tcVNS, (3) 120 min after stimulation, and (4) 240 min after stimulation | ||
| Napadow et al. (2012) | Cefar Acus II (Cefar Medical, Lund, Sweden) | 0.20 × 1.5 mm modified press-tack electrodes (DBC, Korea and Vinco, China) | RAVANS [M (SD) = 0.43 (0.25 mA)] |
450 μS | 30 | 0.5 s and was gated to the exhalation phase of respiration |
Rectangular pulses | (1) the cymba concha (+) and (2) the slope between the antihelix and cavum concha (–) |
30 min | Deep-tissue pain intensity | 15 and 30 min and 14 min after tVNS onset |
| Ventura-Bort et al. (2018) | CMO2, Cerbomed, Erlangen, Germany | Two titan electrodes mounted on a gel frame | M = 1.3 mA (0.4–3.3 mA) | 200–300 μs | 25 | Continuous | Left cymba conchae |
35 min | Oddball and Simon task | 0 min; simultaneous | |
| De Couck et al. (2017) | Cerbomed, Germany | Double ball point electrodes | Mean intensity of 0.7 mA in study 1 and 1 mA in study 2 | 250 μs | 25 | Alternating pulse series of 30 s duration followed by 30 s stimulation pause |
Rectangular pulses | Cymba conchae area of the outer ear; Left ear and right ear in Study 1 and Right ear in Study 2 |
10 min each in Study 1 and 1 h in Study 2 | HRV | Study 1: simultaneous HRV Study 2: HRV was measured during the first 5 min, between minutes 30–35 and between minutes 55–60 of the 1 h stimulation |
| Janner et al. (2018) | Transcutaneous electrical nerve stimulation device PuntoBravo (Medizintechnik Rostock GmbH, Rostock, Germany) |
Self-manufactured electrodes; electrodes' contact surfaces, wrapped in wool, were moistened with 0.9% sodium chloride solution |
M (SD) = 6.8 mA (1.3) for left ear and M (SD) = 8.3 mA (3.9) for right ear | 200 μs | Mixed frequency pattern of 100/2 Hz | 9 impulses with a frequency of 100 Hz emitted twice per second | Electrical square impulses | Bilateral cymbas conchae | 25 min | Heat stimulation | 20 min heat stimulation starts, physio and anxiety assessed 20 and 25 min after tVNS onset |
| Beste et al. (2016) | CM02, Cerbomed, Erlangen, Germany). | Two titan electrodes mounted on a gel frame | 0.5 mA | 200–300 μs | 25 | Active for 30 s, followed by a break of 30 s |
Left inner ear | 60 min | Backward Inhibition Task | Simultaneous | |
| Hong et al. (2019) | Transcutaneous, bipolar stimulation probe (Stimulationssonde 522,015, Inomed) | Bipolar stimulation probe | 10 mA | 250 μs | 25 | Cymba conchae of the right ear | 10 min | Simultaneous physio and blood draw 1 and 3 h post-tVNS | |||
| Colzato et al. (2017) | NEMOS® tVNS | Two titan electrodes mounted on a gel frame | 0.5 mA | 200–300 μs | 25 | Alternated between on and off periods every 30 sec | Outer auditory canal of left ear | 35 min | Reading the Mind in the Eyes Test and physio | 20 min start Reading the Mind in the Eyes Test and physio 20 and 35 min after tVNS onset | |
| Gancheva et al. (2018) | Cerbomed NEMOS® (Cerbomed, GmbH, Erlangen, Germany) | 0.6–1.4 mA for the taVNS cymba conchae condition (0.9 ± 0.1 mA, mean ± SEM) |
0.25 ms duration | 25 | Continuous | Continuous biphasic square pulses | Cymba conchae of the left external ear | 14 min | Physio | Simultaneous physio and up to 2 h post-tVNS | |
| Kraus et al. (2013) | Voltage source (Digitimer Type DS7A, serial D127A) | MRI compatible silver plate (5 mm in diameter) |
Mean stimulation intensity in the active group was 32.6 V (min 14 V, max 57 V, SD 13.4) | 20 ms | 8 | Constant | Left external acoustic meatus on the inner side of the tragus |
Four stimulation periods of 30 s were applied, each followed by a resting period of 1 min | N | Simultaneous MRI | |
| Tobaldini et al. (2019) | TENS device (NEMOS® Cerbomed, Erlangen, Germany) | Surface electrodes | 1–6 mA | 200 ms | 25 | Continuous | Left cymba conchae of the external ear | 25 min | Physio | Simultaneous physio | |
| Yakunina et al. (2018) | Custom-made stimulator (Yakunina et al., 2017) | 0.1 mA weaker than the intensity corresponding to the pain threshold means (SD)= 0.71 (0.43) for tragus and means (SD)= 0.80 (0.47) for the concha |
500 μs | 25 | Each location was stimulated in two runs with 30 s of stimulation followed by 30 s of rest; this cycle was repeated five times in a run. Each subject underwent a total of six 5-min fMRI runs, with up to 90 s of rest between run |
Monophasic rectangular impulse | Inner tragus and cymba conchae of the left ear | 25 min runs per location | MRI | Simultaneous MRI | |
| Kraus et al. (2007) | EMP2 Expert, schwa-medico GmbH, Ehringshausen, Germany | Silver plate (5 mm in diameter) | Mean intensity for LOW was 4.0 mA (SD 1.0) while for HIGH it was 5.0 mA (SD 1.0) | 20 ms | 8 | Three stimulation sequences were applied, each of which consisted of a stimulation period of 30 s, followed by a resting period of 2 min. The first two sequences were performed with low stimulation intensity (LOW) and the last one with high intensity (HIGH) |
Left external acoustic meatus on the inner side of the tragus | 30 s | MRI | Simultaneous MRI | |
| Keute et al. (2018) | Medical stimulation device (Digitimer DS7, UK) | Two conventional neurostimulation electrodes Ambu Neuroline, DK 4 × 4 mm | 8 mA, if tolerable for the subject, and else individually adjusted below pain threshold 5.9 ± 1.6 mA |
200 μs | 25 | Trains of 30 s, each followed by 30 s without stimulation | Monophasic square pulses |
Cymba conchae of the left ear; anode being more rostral | 25 min | Negative compatibility effect (NCE) task and EEG | 25 min; not simultaneous |
| Sellaro et al. (2015a) | CM02, Cerbomed, Erlangen, Germany | Two titan electrodes fastened on a gel frame | 0.5 mA | 200–300 μs | 25 | On/Off periods every 30 s | Outer auditory canal of the left ear | 30 min | Measured mood/physio data and started cyberball 20 min into stimulation and at the end of stim | ~20 and 30 min | |
| Dietrich et al. (2008) | Stand-alone electrical nerve stimulator connected with carbon fiber wires to an acrylic electrode array housing a sterling silver stimulation electrode and a reference electrode | Sterling silver stimulation electrode and a reference electrode; The array was attached to the skin with an adhesive tape |
Varied individually between 4 and 8 mA | 250 μs. | 25 | The experiment lasted 700 s and was started with a baseline lasting 100 s. This was followed by a first stimulation period of 50 s and a break/baseline of 100 s. Four alternating |
Monophasic-modified rectangle impulse | Inner side of the left tragus | 700 s | Simultaneous MRI | Simultaneous MRI |
| stimulation and baseline sequences were performed | |||||||||||
| Frangos and Komisaruk (2017) | Hand-held battery-operated stimulation device | A pair of non-ferromagnetic stainless steel surface electrodes (1 cm diameter) |
23.9 ± 12.3 V | 200 μs (1/5,000 Hz = pw in s) | 25 | 1-ms duration bursts of 5 sinusoidal wave pulses; continuous | Right antero-lateral surface of the neck | 2 min | MRI | Simultaneous MRI and rest up to 15 min after tVNS offset | |
| Frangos et al. (2015) | Cerbomed NEMOS | Two hemispheric titanium electrodes | Earlobe: 0.3–0.9 mA Cymba conchae: 0.3–0.8 mA |
25 | Continuous | 0.25 m-duration monophasic square wave pulse | Left cymba conchae, left earlobe | 7 min | |||
| Juel et al. (2017) | Nemos® cerbomed GmbH, Erlangen, Germany | Bipolar stimulation electrode | Ranged from 0.1 to 10 mA | 250 μs | 30 | Continuous | Left concha | 60 min | Quantitative sensory testing (QST) Conditioned pain modulation (CPM) paradigm Gastroduodenal motility parameters Vagal Tone Deep Slow Breathing |
15- and 30-min after tVNS onset-start DSB for 10 min; Vagal and QST 10 and 25 min after tVNS onset and CPM 40 min post tVNS onset and motility 50 min after tVNS onset | |
| Fallgatter et al. (2005) based on Fallgatter et al. (2003) | Two conventional bipolar electrode wires soldered to single-sided copper claddings at the input side. At the output side, two very flexible fine copper stranded wires (length |
Stimulation electrode was a piece of epoxy resin (about 1 × 1 cm) | 8 mA | 0.1 ms duration | 0.1 ms duration, the interstimulus interval was 2 s |
Electrical square impulses | Cathode of this bipolar stimulation electrode was placed at the inner side of the tragus at the outer ventral edge of the internal auditory meatus. The anode was placed 5 mm | Vagus sensory evoked potential (VSEP) | Concurrent VSEP | ||
| ~10 cm, diameter (0.05 mm) were soldered to the copper claddings. The other end of these wires was fixed to the skin with a very small amount of Grass paste | more distal at the inner side of the tragus | ||||||||||
| Tran et al. (2019) | Transcutaneous electrical nerve stimulation (TENS) unit | Ear clip electrode (Parasym device, Parasym Health, Inc., London, UK) |
1 mA below the discomfort threshold | 200 μs | 20 | Tragus of the ear | 1 h | ECG | HRV after 55 min of tVNS and Echocardiography 40 min after tVNS onset | ||
| Szeska et al. (2020) | CMO2, Cerbomed, Erlangen, Germany | Two titan electrodes mounted on a gel frame | Active tVNS: average 2.28 mA Sham: average 2.53 mA |
200–300 μs | 25 Hz | 30 s on, 30 s off | Active tVNS: cymba conchae Sham: center of earlobe |
8 min | Multiple-day single-cue fear conditioning and extinction paradigm | 3 min | |
| Giraudier et al. (2020) | CMO2, Cerbomed, Erlangen, Germany | Two titan electrodes mounted on a gel frame | Active tVNS: 0.5–3.5 mA, average 1.48 Sham: 0.5–2.5 mA, average 1.31 |
200–300 μs | 25 Hz | 30 s on, 30 s off | Left cymba conchae |
23 min | Lexical decision task and recognition memory task | 5 min; simultaneous; 5 min. (post) | |
| Neuser et al. (2019) | NEMOS, Cerbomed GmbH, Erlangen, Germany | Titanum electrode | Active tVNS: 0.2–3.1 mA Sham: 0.5–3.1 mA N = 81 N = 41 completed task during left side taVNS N = 40 completed task during right-sided taVNS |
25 Hz | 30 s on, 30 s off | Biphasic impulse frequency | Active tVNS: cymba conchae Sham: earlobe |
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| Bretherton et al. (2019) Study 1, 2 |
TENS machine (V-TENS Plus, Body Clock Health Care Ltd, United Kingdom) | Auricular electrode clips attached on the inner and outer surface of the tragus of the ear (Auricular Clips, Body Clock Health Care Ltd, UK) | 2–4 mA | 200 μs | 30 Hz | Inner and outer surface of the tragus of the ear (Auricular Clips, Body Clock Health Care Ltd, UK) | 15 min | ||||
| (Teckentrup et al., 2020) | NEMOS, Cerbomed, Erlangen, Germany | Individually adapted stimulus intensity (see Frangos et al., 2015) | 25 Hz | 30 s on, 30 s off | Biphasic impulse frequency | taVNS: left cymba conchae Sham: left earlobe |
30 min | ||||
| Zhang et al. (2019) | MRI compatible Electronic Acupuncture Treatment Instrument (SDZII, Huatuo, Suzhou, China) | 1.5–3 mA | 0.2 ms | 1 Hz | Continuous wave 20 s on vs. 30 or 20 s off block design of intermittent taVNS | taVNS: left cymba conchae Sham: left tail of the helix |
13 min |
a
Electrode consisting of two stainless steel straps, wrapped with wool fiber and stapled to a 9 × 9 mm piece of silicon rubber.
b
Silver plate was placed in the left ear triangular fossa; the cylindrical electrode was placed in the left cymba concha.
c
Plate electrode was placed in the left external acoustic meatus on the inner side of the tragus; the cylindrical electrode was placed on the left lower limb (left middle shank).