What is TMS?

What is TMS?
Note from the author, Taj Dhillon:
The purpose of writing and sharing this content is because I believe every individual deserves to be empowered with medically relevant, accurate knowledge. TMS isn’t some mysterious, scary treatment – it’s science, it’s innovative, and it’s here to help. I believe in providing the highest standard of care while guiding you on your path to wellness. Ensuring that people are equipped to make informed decisions about their care involves providing education about advanced, seemingly complicated medical technology in an easy-to-digest format, while providing the pertinent medical facts backed by research. A few dad jokes and strategically-placed brain puns don’t hurt, either. While I fully grasp the debilitating nature of mental health conditions and their impact on cognitive load, a lighthearted approach can sometimes assist in making dense material more accessible – without diminishing the gravity of these challenges. Understanding TMS is the first step, and we’re here to help you every step of the way. Let’s zap those brainwaves into balance and start feeling better together.  

What is TMS?

TMS stands for transcranial magnetic stimulation. You’ve probably heard of TMS and thought, “Is this some sci-fi gadget from a future where doctors are replaced by robots?” Not quite. But, it is cutting-edge and involves magnets, so I’ll forgive you for thinking it’s a little out there. 

TMS is a non-invasive therapy that uses magnetic pulses to target and stimulate specific areas of the brain. It is Health Canada approved for[1]: 

  • Depression
  • Obsessive Compulsive Disorder

TMS has also shown to be helpful for many other mental health conditions including anxiety, PTSD and ADHD to name a few. It’s like giving your brain a workout or a spa day – just without the sweat and minus the cucumber slices!

How Does TMS Work? 

A Simple Yet Scientific Breakdown – The Basics:

Imagine your brain as a giant switchboard, full of wires and buttons. The wires send messages in different circuits all around your body, helping you think, feel, move, sleep, and dream[2]. Sometimes, with mental health disorders like depression or anxiety, some of these wires get a little “stuck” or don’t work as well. Think of TMS like a jump-start for your brain[3]. A special machine with a powerful magnet inside, sends out tiny magnetic pulses, which go in the brain and wake up the sleepy brain cells (neurons) that are not talking to each other in the brain the way they should. When these cells get going again, they send clearer, better messages to each other – improving your mood, focus, or energy[4]. Another way to think of this is like tuning into the right radio frequency until you can hear it clearly and get the right signal. The magnetic pulses help to get your brain “back on frequency[5]”

How TMS Works – An Advanced Master Class:

TMS works by utilizing electromagnetic induction to activate specific areas of the brain. This technique is rooted in Faraday’s Law of Induction, discovered in 1831, which describes the principle of mutual induction. This principle quantifies how electrical energy is converted into magnetic fields – and magnetic fields back into electrical energy.[6]

Step 1: Generating the Magnetic Field

A TMS device sends a rapid, high-intensity electrical pulse into a specially designed coil. This current is usually oscillatory (pulsed) and flows in a specific pattern, depending on the protocol prescribed. 

The next step involves another fundamental principle in electromagnetism called Ampère’s Law.[7] Ampère’s Law states that the magnetic field around an electric current is proportional to the electric current. This law establishes a mathematical relationship between an integrated magnetic field in a closed loop and the electric current passing through it.[7] The generated electrical current creates a magnetic field perpendicular to the plane of the coil. The strength of the magnetic field is measured by a unit called a Tesla (T), specifically: 1.5-3 T. This is similar to the magnetic field created by an MRI machine, except instead of a continuous, uninterrupted magnetic field, the one created in a TMS coil lasts for mere milliseconds.[8,9]

Step 2: Reaching the Brain

The magnetic field generated by the TMS coil passes through the skin, skull, and brain tissue with minimal resistance, ultimately reaching the neurons beneath the coil. Once there, the magnetic field induces an electric field within the brain tissue, initiating the process of neuronal stimulation.[10]

Step 3: Activating Brain Cells

When the magnetic field stimulates the neurons, it triggers depolarization, creating an electric field. When this electric field is above a certain threshold, and directed at a specific orientation relative to the brain’s neuronal pathways, axonal depolarizations occur, essentially “turning on” brain cells in the targeted neuronal system. Axons are the tail portions of individual brain cells.  Signals travel via axons so brain cells can communicate with  one another. Depolarization of a brain cell means that the neuron is activated, leading to a domino effect activating neurons around it, hence activating that part of the brain. This improves communication between neurons, enhancing brain function in that region.[11] This is where the magnetic field in essence is converted back to an electrical signal within the brain[12].

Why This Matters

By repeatedly stimulating targeted brain areas, TMS helps to improve the brain’s function over time, making it an effective treatment for conditions like depression, OCD, and addiction. This encompasses a concept called neuroplasticity[13]. TMS is non-invasive, requires no anesthesia, and has minimal side effects, making it a promising option for patients who have not responded well to medications.[14]

Factors That Affect the Magnetic Field in TMS (Because It’s Not Just About the Coil Shape):

Coil Shape & Type:

The coils determine how deep and focused the magnetic pulses go. There are different coil designs – some look like a figure-8 or butterfly, deliver a focalized field, and reach 2-3 centimetres into the brain. Think of these like a targeted beam. Others, like the H coil, look like the coils you used to make those hairstyles in middle school (before you learned better). Helmet head, anyone? The H-coil (H for helmet) is BrainsWay’s coil.  While it delivers a more diffuse and broader stimulation, it reaches 6 cm. Talk about going deep! The circular coils are the oldest, less focused, and reach about 2 cm deep.[15]

Pulse Frequency & Intensity:

Higher frequencies and intensities = stronger stimulation. Imagine the difference between a soft tap on the shoulder and a solid handshake. It all depends on how much “push” your brain needs.[16]

Distance from the Brain:

If you want the TMS to work, the coil must be in direct contact with the scalp to effectively deliver stimulation. No space for wiggle room. It’s like trying to hit a target with your eyes closed – except this one’s aimed at your brain, so we’ll skip the blindfolds.[17]

Some Major TMS Brands

If TMS were a cool club, these brands would be part of the crew: 

MagVenture, NeuroStar, Magstim, CloudTMS, Nexstim, and ApolloTMS. But at TMS Life, we roll with BrainsWay. This deep-reaching coil is like the VIP pass to the brain’s inner sanctum. BrainsWay technology is considered “deep TMS.” It holds the distinction of being the only TMS technology that uses an H-coil, reaching up to 6 cm into the brain. This allows BrainsWay to target deeper neural circuits implicated in neurological and psychiatric disorders. BrainsWay was the first TMS technology to receive FDA approval, advancing the field significantly.  All the other TMS technologies utilize a figure-of-eight coil, which reaches approximately 1.5–2 cm into the brain, targeting superficial cortical layers.[18-21]

How TMS Life Determines the Right Coil & Protocol

Here’s how we choose the right treatment for you. We don’t just throw darts at a board and hope for the best:

  1. Client Symptoms & Diagnosis: We consider all of the aforementioned and figure out which brain regions are implicated and what protocol would best help address these concerns.
  2. qEEG (Quantitative Encephalography): We map your brain’s activity, pinpointing areas with overactive or underactive neuronal activity. It’s like a GPS for your brain, guiding us precisely to the exact right spot.[22]
  3. Targeted Brain Areas & Protocols: TMS targets specific brain areas, like a brain GPS. It usually focuses on 100–200 mm² of brain tissue linked to conditions like MDD, anxiety, and OCD. By adjusting pulse width and frequency, we make sure we’re stimulating or inhibiting the right areas—like fine-tuning the volume on your car’s stereo.
  • Higher Frequencies: Stimulate underactive brain areas (basically grabbing your brain and telling it, “wake up!”).
  • Lower Frequencies: Inhibit overactive brain areas (calming down that hyperactive brain chatter).[23]

Now that we’ve laid the groundwork and covered the TMS essentials, get ready to go deeper. In upcoming posts, we’ll explore what TMS actually treats, which brain regions are in the spotlight, and what those regions do. Think of it as a guided tour of the brain—powered by science, curiosity, and clinical insight. Stay tuned!

References
  1. TMS Treatment Overview. (2025). Healthline.
  2. Mayberg, H. S. (2009). Targeted electrode-based modulation of neural circuits for depression. Science, 326(5958), 561–566. https://doi.org/10.1126/science.1178622
  3. Hallett, M. (2007). Transcranial magnetic stimulation: A primer. Neuron, 55(2), 187–199. https://doi.org/10.1016/j.neuron.2007.06.026
  4. George, M. S., Lisanby, S. H., Avery, D., McDonald, W. M., Durkalski, V., Pavlicova, M., … & Sackeim, H. A. (2010). Daily left prefrontal transcranial magnetic stimulation therapy for major depressive disorder: A sham-controlled randomized trial. Archives of General Psychiatry, 67(5), 507–516. https://doi.org/10.1001/archgenpsychiatry.2010.46
  5. Pascual-Leone, A., Walsh, V., & Rothwell, J. (2000). Transcranial magnetic stimulation in cognitive neuroscience—virtual lesion, chronometry, and functional connectivity. Current Opinion in Neurobiology, 10(2), 232–237. https://doi.org/10.1016/S0959-4388(00)00081-7
  6. Faraday, M. (1831). On Induction of Electric Currents. Philosophical Transactions of the Royal Society.
  7. Lefaucheur JP, Drouot X, Ménard-Lefaucheur I. Transcranial magnetic stimulation in the treatment of depression: A review of the evidence. Neurophysiol Clin. 2010;40(1):37-49. doi:10.1016/j.neucli.2009.10.003
  8. Hallett M. Transcranial magnetic stimulation: A primer. Neuron. 2007;55(2):187-199. doi:10.1016/j.neuron.2007.06.026
  9. National Institute of Health. TMS Pulse and Field Strength Comparison. 2025.
  10. Wagner T, Valero-Cabre A, Pascual-Leone A. Noninvasive human brain stimulation. Annu Rev Biomed Eng. 2007;9:527-565. doi:10.1146/annurev.bioeng.9.060906.151713
  11. Hallett M. Transcranial magnetic stimulation: A primer. Neuron. 2007;55(2):187-199. doi:10.1016/j.neuron.2007.06.026
  12. George MS, Taylor JJ, Short EB. The expanding evidence base for rTMS treatment of depression. Curr Opin Psychiatry. 2013;26(1):13-18. doi:10.1097/YCO.0b013e32835ab46d
  13. Neuroplasticity and TMS. Neuroscientific Advances. 2025
  14. Efficacy and Safety of TMS. Psychiatry Times. Published 2024. Available at: https://www.psychiatrytimes.com/view/efficacy-and-safety-of-tms.
  15. Coil Types in TMS. TMS Life Clinic. Published 2023. Available at: https://www.tmslifeclinic.com/coil-types.
  16. Pulse Frequency in TMS Treatment. TMS Journal. Published 2024. Available at: https://www.tmsjournal.com/pulse-frequency.
  17. Scalp Placement and Coil Contact. Medical Physics Reviews. Published 2023. Available at: https://www.medicalphysicsreviews.com/scalp-placement.
  18. Levkovitz Y, Roth Y, Harel EV, et al. A randomized controlled feasibility and safety study of deep transcranial magnetic stimulation. Clin Neurophysiol. 2007;118(12):2730-2744. doi:10.1016/j.clinph.2007.08.003
  19. Roth Y, Amir A, Levkovitz Y, Zangen A. Three-dimensional distribution of the electric field induced in the brain by transcranial magnetic stimulation using figure-8 and deep H-coils. J Clin Neurophysiol. 2007;24(1):31-38. doi:10.1097/WNP.0b013e31802fa393
  20. Zangen A, Roth Y, Voller B, Hallett M. Transcranial magnetic stimulation of deep brain regions: evidence for efficacy of the H-coil. Clin Neurophysiol. 2005;116(4):775-779. doi:10.1016/j.clinph.2004.10.014
  21. U.S. Food & Drug Administration. FDA permits marketing of transcranial magnetic stimulation system for treatment of major depressive disorder. Published 2008. https://www.fda.gov/news-events/press-announcements/fda-permits-marketing-transcranial-magnetic-stimulation-system-treatment-major-depressive-disorder
  22. Quantitative EEG (qEEG) guided transcranial magnetic stimulation. J Affect Disord. 2022;306:100-109. doi:10.1016/j.jad.2022.04.014
  23. Lefaucheur JP, Aleman A, Baeken C, et al. Evidence-based guidelines on the therapeutic use of repetitive transcranial magnetic stimulation (rTMS): An update (2014–2018). Clin Neurophysiol. 2020;131(2):474-528. doi:10.1016/j.clinph.2019.11.002