Clinical education
From magnet to neurons
A rapidly changing magnetic field induces an electric current — this is Faraday's principle, and it is exactly how rTMS works. When a current passes through the coil held against your scalp, it generates a magnetic field that passes unimpeded through skin, bone and tissue, and in turn induces a small, controlled electrical current in the brain's outer few centimetres.
That induced current briefly depolarises neurons near the surface, causing them to fire. Applied repeatedly — 'repetitive' TMS — these pulses change how the targeted network behaves over time, in ways that depend on the pattern of stimulation.
Clinical education
Excitation, inhibition and network effects
The parameters of stimulation matter enormously. High-frequency stimulation (around 10 Hz) generally increases cortical excitability, while low-frequency stimulation (around 1 Hz) tends to reduce it. More recent patterns such as intermittent theta burst stimulation deliver pulses in brief bursts that achieve effects in a shorter session.
In depression, the usual target is the left dorsolateral prefrontal cortex — a region strongly connected to mood-regulating circuits deep in the brain. Stimulating this 'control tower' appears to influence wider networks whose under-activity is associated with depressive illness.
Clinical education
Why the protocol matters as much as the device
Two patients can sit under the same machine and receive completely different treatments. The target (which scalp position, and how it is located), the frequency, the number of pulses per session, the intensity relative to the individual's motor threshold, and the total number of sessions together define the treatment. Evidence exists for specific protocol families — which is why a specialist plans the protocol rather than defaulting to a machine's menu.
- Target: where stimulation is applied, typically guided by standard scalp measurement systems
- Intensity: set relative to each patient's own motor threshold, measured at first visit
- Protocol: frequency, pattern and duration of stimulation
- Course: number of sessions and schedule
Clinical education
What rTMS is not
rTMS is not a shock treatment, does not involve anaesthesia, does not cause convulsions in normal use, and is not the same as deep brain stimulation — a surgical implant. It is also not a passive therapy: its evidence base is strongest when combined with appropriate medication, psychological treatment and clinical follow-up.
This content is awaiting clinical review and is shown here as an editorial draft.