Changing brain activity from outside the skull: transcranial magnetic stimulation for research and depression, weak electrical currents (tDCS) and their hype, and the history and modern reality of electroconvulsive therapy.
Tools & Methods
Intermediate
Brain Stimulation: TMS, tDCS and ECT
The Editors
August 10, 2026
3 min read
In plain English
Brain stimulation techniques change brain activity from outside the head. TMS uses magnetic pulses to briefly activate or disrupt a small area — useful for research and approved to treat depression and OCD. tDCS uses very weak electrical currents with much smaller, debated effects. ECT, done under anaesthesia, remains a highly effective treatment for severe depression.
Intermediate level: Builds on the basics. Introduces the real vocabulary and the mechanisms behind it.
Concepts to know first
Transcranial magnetic stimulation
In 1985 Anthony Barker and colleagues in Sheffield demonstrated transcranial magnetic stimulation (TMS): a coil held against the head passes a brief, strong current, generating a rapidly changing magnetic field that passes painlessly through the skull and induces small electrical currents in the cortex beneath. A single pulse over the motor cortex makes a hand muscle twitch; over the visual cortex it can produce flashes of light (phosphenes).
In research, TMS can create a temporary "virtual lesion", briefly disrupting a region to test whether it is necessary for a task — for example, a pulse over the occipital cortex at the right moment can stop people seeing a briefly flashed letter. Combined with EEG, TMS measures how the brain responds to a perturbation, used to assess consciousness.
In treatment, repeated pulses (rTMS) can change cortical excitability for longer periods. The US FDA cleared rTMS for treatment-resistant depression in 2008, usually targeting the left dorsolateral prefrontal cortex in daily sessions over several weeks; "deep TMS" was cleared for OCD in 2018 and for smoking cessation in 2020. Accelerated protocols using brain-imaging-guided targeting and many sessions per day (such as the SAINT protocol, cleared in 2022) aim for faster responses.
Transcranial direct current stimulation
tDCS passes a weak constant current (typically 1–2 milliamps) between electrodes on the scalp, nudging neurons slightly toward or away from firing. It's cheap and portable, and consumer devices have been marketed for focus and learning. However, results have been inconsistent, much of the current is shunted through the scalp, and many effects have not replicated well. It remains an active research tool, with some evidence for specific clinical uses.
Electroconvulsive therapy
ECT was introduced in 1938 by the Italian psychiatrists Ugo Cerletti and Lucio Bini. Early ECT, given without anaesthesia, could cause fractures and fear, and its portrayal in films such as One Flew Over the Cuckoo's Nest shaped public views. Modern ECT is done under general anaesthesia with muscle relaxants, deliberately inducing a brief seizure. It is one of the most effective treatments for severe, treatment-resistant or psychotic depression and catatonia, often working faster than medications. Side effects include temporary confusion and memory problems, particularly for events around the treatment period.
Everyday examples & things to try
Real world
A virtual lesion in seconds
In TMS experiments on speech, a few seconds of stimulation over Broca's area can make a fluent speaker stumble — temporarily and harmlessly reproducing a mild version of what a stroke there might cause. That's how TMS tests whether a region is needed for a task.
Key takeaways
- TMS (1985) uses magnetic pulses to activate or disrupt cortex; rTMS is approved for depression and OCD.
- tDCS uses weak currents with inconsistent, debated effects.
- Modern ECT under anaesthesia is highly effective for severe depression.
Explore further
Search YouTube for…
Tap a phrase to copy it, then paste it into YouTube's search box. This site doesn't link to other websites — pick channels from universities, hospitals and established science educators.
Tagsmethodstmstdcsectdepression
Keep reading
Tools & Methods
Intermediate
EEG and MEG
Recording the brain's electrical rhythms through the scalp, from Hans Berger's alpha waves in the 1920s to event-related potentials, sleep studies, epilepsy diagnosis and wearable magnetoencephalography.
August 6, 2026 · 3 min read
Tools & Methods
Intermediate
Animal Models in Neuroscience
Why neuroscience studies worms, flies, fish, mice, rats, songbirds and monkeys; what each species offers; the limits of translating animal findings to humans; brain organoids; and the ethics of the 3Rs.
December 8, 2025 · 3 min read
Tools & Methods
Advanced
Connectomics: Mapping Every Connection
From the 302-neuron worm in 1986 to a complete fruit-fly brain in 2024, a cubic millimetre of human cortex and mouse visual cortex in 2025: how scientists map neural wiring synapse by synapse, and what the maps reveal.
November 13, 2025 · 3 min read