SimTMS
TREN

TMS training simulator · runs in the browser

Find the motor hotspot. Measure the motor threshold.

simHotpoint, the first module of the SimTMS family, teaches the two core skills of transcranial magnetic stimulation (TMS), one step at a time: placing a figure-of-eight coil on a holder to find the motor hotspot of a hand muscle, and determining the resting motor threshold (rMT) the way clinical guidelines describe it. All before you work with a real person.

Open simHotpoint → Read the guide

Turkish and English · nothing to install · electric fields computed with SimNIBS

Head from above: Cz, a hotspot over the left motor cortex with a figure-of-eight coil and holder on it; an MEP recording in the corner Cz C3 Nasion Inion EMG · APB p-p 2.1 mV
Hand-area hotspot over the left motor cortex (around C3), handle 45° backward and lateral; the MEP on the right is measured peak to peak.

How a session runs

Each step builds on the previous one. Every new virtual subject has a different hotspot and threshold, so you find them by method, not by memory.

  1. PreparationChoose the target muscle (APB, FDI, ADM, biceps, tibialis anterior) and place the EMG electrodes.
  2. Find CzMark the vertex, then check and correct it with a tape measure along the nasion–inion and tragus lines.
  3. Starting pointMove the coil to the textbook starting point for the chosen muscle (around C3 for the right hand).
  4. Coil orientationTurn the handle about 45° backward and lateral so the induced current flows posterior to anterior (PA).
  5. Hotspot searchFire single pulses at any site and intensity, read each MEP, build a map and lock the best site.
  6. Motor thresholdDetermine rMT with the relative-frequency rule: ≥ 50 µV in at least half of the trials.
  7. EvaluationSee your score, your errors, and the field your locked coil pose produces in a real SimNIBS head model.

Why the hotspot and threshold matter

Every dose is a percentage of threshold

rTMS intensity is prescribed as a percentage of motor threshold; the pivotal multisite depression trial used 120% of rMT (O'Reardon et al., 2007). A threshold measured away from the hotspot comes out too high, and the treatment dose rises with it.

Watching for a twitch is not enough

Setting threshold by watching for a muscle twitch gave values on average 11.3% higher than the EMG threshold; dosing rTMS from it would have exceeded safety limits in more than half of the subjects (Westin et al., 2014).

The reference for everything else

MEP amplitude, input–output curves and paired-pulse measures are all recorded at the hotspot, and coil orientation is at least as critical as position (Rossini et al., 2015). Details and a comparison of methods are in the guide.

Real physics, stated assumptions

Electric fields from SimNIBS

The evaluation step and the E-field explorer show fields computed by finite-element modelling in SimNIBS 4.6 (Thielscher et al., 2015; Saturnino et al., 2019): the "ernie" example head model (Puonti et al., 2020) and the MagVenture MC-B70 model from the validated coil database (Drakaki et al., 2022). The coil is drawn on the scalp in the exact pose the simulation used.

MEP model

The MEP is a sigmoid input–output function of effective stimulation (Devanne et al., 1997) with trial-to-trial variability (Kiers et al., 1993). Responses depend on coil orientation (Mills et al., 1992; Brasil-Neto et al., 1992). Spatial fall-off is calibrated from a SimNIBS sensitivity analysis: a 10 mm shift lowers the field at the target by about 13%.

Limits

SimTMS is a teaching tool, not for clinical decisions, diagnosis or certification. The virtual subject's anatomy is simplified. The SimNIBS card covers one example head and coil positions around the hand area (C3).

Who it is for

  • Neurology residents
  • Clinical neurophysiology trainees
  • Psychiatry rTMS teams
  • TMS researchers and technicians
  • Medical and neuroscience students

Author

SimTMS is developed by Prof. Dr. Burhanettin Uludağ.

How to cite

Uludağ B. SimTMS · simHotpoint: TMS motor hotspot and motor threshold training simulator [software]. 2026. https://burhanettinuludag.com.tr/simtms/en/

References

Guidelines and methodological standards

  1. Rossini PM, Burke D, Chen R, et al. Non-invasive electrical and magnetic stimulation of the brain, spinal cord, roots and peripheral nerves: basic principles and procedures for routine clinical and research application. An updated report from an I.F.C.N. Committee. Clin Neurophysiol. 2015;126(6):1071-107. PMID 25797650 · doi:10.1016/j.clinph.2015.02.001

Safety and treatment dosing

  1. O'Reardon JP, Solvason HB, Janicak PG, et al. Efficacy and safety of transcranial magnetic stimulation in the acute treatment of major depression: a multisite randomized controlled trial. Biol Psychiatry. 2007;62(11):1208-16. PMID 17573044 · doi:10.1016/j.biopsych.2007.01.018

Physiology and MEP measurement

  1. Brasil-Neto JP, Cohen LG, Panizza M, Nilsson J, Roth BJ, Hallett M. Optimal focal transcranial magnetic activation of the human motor cortex: effects of coil orientation, shape of the induced current pulse, and stimulus intensity. J Clin Neurophysiol. 1992;9(1):132-6. PMID 1552001
  2. Devanne H, Lavoie BA, Capaday C. Input-output properties and gain changes in the human corticospinal pathway. Exp Brain Res. 1997;114(2):329-38. PMID 9166922 · doi:10.1007/pl00005641
  3. Kiers L, Cros D, Chiappa KH, Fang J. Variability of motor potentials evoked by transcranial magnetic stimulation. Electroencephalogr Clin Neurophysiol. 1993;89(6):415-23. PMID 7507428 · doi:10.1016/0168-5597(93)90115-6
  4. Mills KR, Boniface SJ, Schubert M. Magnetic brain stimulation with a double coil: the importance of coil orientation. Electroencephalogr Clin Neurophysiol. 1992;85(1):17-21. PMID 1371739 · doi:10.1016/0168-5597(92)90096-t

Motor threshold methods

  1. Westin GG, Bassi BD, Lisanby SH, Luber B. Determination of motor threshold using visual observation overestimates transcranial magnetic stimulation dosage: safety implications. Clin Neurophysiol. 2014;125(1):142-7. PMID 23993680 · doi:10.1016/j.clinph.2013.06.187

Electric-field modelling and SimNIBS

  1. Drakaki M, Mathiesen C, Siebner HR, Madsen KH, Thielscher A. Database of 25 validated coil models for electric field simulations for TMS. Brain Stimul. 2022;15(3):697-706. PMID 35490970 · doi:10.1016/j.brs.2022.04.017
  2. Puonti O, Van Leemput K, Saturnino GB, Siebner HR, Madsen KH, Thielscher A. Accurate and robust whole-head segmentation from magnetic resonance images for individualized head modeling. Neuroimage. 2020;219:117044. PMID 32534963 · doi:10.1016/j.neuroimage.2020.117044
  3. Saturnino GB, Puonti O, Nielsen JD, Antonenko D, Madsen KH, Thielscher A. SimNIBS 2.1: a comprehensive pipeline for individualized electric field modelling for transcranial brain stimulation. In: Makarov S, Horner M, Noetscher G, editors. Brain and Human Body Modeling: Computational Human Modeling at EMBC 2018. Cham (CH): Springer; 2019. p. 3-25. PMID 31725247 · doi:10.1007/978-3-030-21293-3_1
  4. Thielscher A, Antunes A, Saturnino GB. Field modeling for transcranial magnetic stimulation: a useful tool to understand the physiological effects of TMS? Annu Int Conf IEEE Eng Med Biol Soc. 2015;2015:222-5. PMID 26736240 · doi:10.1109/EMBC.2015.7318340