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Interactive Simulation

See How TMS Targets the Brain

Transcranial magnetic stimulation uses focused electromagnetic fields to stimulate specific cortical regions. Explore the science below.

How TMS Works

A step-by-step explanation of what happens during a TMS session.

Step 1

Targeting

A figure-8 coil is positioned over the target brain region — typically the left dorsolateral prefrontal cortex (DLPFC) for depression.

Step 2

Magnetic Pulse

Rapidly alternating current in the coil produces a magnetic field (1.5–3 Tesla) that painlessly penetrates the skull and scalp.

Step 3

Neuron Activation

The changing magnetic field induces an electric current in cortical neurons, causing depolarization and downstream neurotransmitter effects.

Treatment Targets by Condition

Different TMS protocols target different brain regions depending on the condition being treated.

Major Depressive Disorder

FDA-cleared 2008
Target: Left DLPFC
10 Hz (high-frequency)
36 sessions over 9 weeks

Anxiety & Depression

Off-label
Target: Right DLPFC
1 Hz (low-frequency)
30–36 sessions

OCD

FDA-cleared 2018
Target: mPFC / ACC
20 Hz intermittent theta burst
29 sessions over 6 weeks

Smoking Cessation

FDA-cleared 2020
Target: Left DLPFC / Insula
10 Hz
13 sessions over 3 weeks

Migraine

FDA-cleared
Target: Motor Cortex
Single-pulse (MagStim)
Variable protocol

PTSD

Off-label (research)
Target: Right DLPFC / mPFC
1 Hz low-frequency
36 sessions

The E-Field: Where the Magic Happens

The electric field (E-field) induced by TMS is what actually stimulates neurons. Its strength and spatial distribution depend on coil geometry, stimulation intensity (expressed as % of motor threshold), and the conductivity of overlying tissue.

1
Peak intensity near the coil
E-field strength decays rapidly with distance — typically 50–80% reduction 1–2 cm from the cortex.
2
Focality vs. depth tradeoff
Figure-8 coils are most focal. H-coils (BrainsWay) reach deeper regions but with less focality.
3
Individual anatomy matters
Skull thickness, CSF depth, and cortical folding all affect field distribution — SimNIBS head models account for this.
E-Field Quick Facts
Typical TMS intensity 100–120% Motor Threshold
Peak E-field at cortex 40–80 V/m
Pulse duration ~200 microseconds
Spatial resolution ~0.5–1 cm² cortical area
Peak magnetic field 1.5–3 Tesla
Pulse frequency range 1–50 Hz
Medical Disclaimer

This is an educational visualization only — it does not represent real patient data or real-time simulation results. For actual TMS treatment planning, tools like SimNIBS are used to compute subject-specific E-fields. Always consult a qualified TMS provider for treatment decisions. Find a TMS specialist →