Transcranial Magnetic Stimulation Lab
Department of Psychology
Social Sciences Building
Ground floor, Room DG22
Tel: +44 (0)20 7040 4561
An Introduction to TMS
What is TMS?
Transcranial magnetic stimulation, or TMS, is a relatively recent technique for stimulating the outer layer of the brain, particularly the cerebral cortex. Brain cells, known as neurones, pass messages by generating spikes of electrical activity, known as action potentials. In TMS, a rapidly changing magnetic field is induced in a hand-held coil in order to electrically activate the neurones in a small area of cortex located under the coil.
What different kinds of TMS are there?
Broadly speaking, TMS comes in three varieties. In single-pulse TMS, stimulation is delivered once every few seconds. In paired-pulse TMS, two TMS pulses are fired very close together in time to see how they interact. Finally, in repetitive TMS or rTMS, a train of pulses are delivered at a rate varying from once per second to 50 or even 100 times per second.
What is TMS used for?
TMS is used for both clinical and research purposes. Clinically, TMS can be used as a diagnostic tool to assess whether the nervous system is working properly. TMS is applied to the part of the brain that sends commands to the muscles of the body (the primary motor cortex) and the speed with which a muscular response occurs is measured. TMS has also been used to treat conditions such as depression. Research investigating the usefulness of TMS for treating neurological and psychiatric conditions is ongoing, but please note that we do not run clinical trials or provide TMS as a therapy/treatment at City.
In cognitive neuroscience research, TMS is used to determine how the brain controls our behaviour. Paired-pulse TMS is used to figure out the ways in which different parts of the brain are connected together. Single-pulse TMS is used to activate muscles of the body and assess the state of the motor system in different experimental conditions. Finally, both single-pulse and repetitive TMS can be used to briefly interfere with the activity of a small area of the brain, so we can see how behaviour is affected. By temporarily turning off a small part of the brain, this approach yields insights that are similar to those obtained by neuropsychologists, who study patients with lesions (damage) to particular areas. Hence TMS is sometimes described as a "virtual lesion" technique.
What does TMS feel like?
TMS feels a little like being tapped on the head. Most people don't really notice it after the first few pulses. However, because TMS can activate muscles on the scalp, it is sometimes experienced as being uncomfortable. In these cases, it may give rise to a short-lived headache. Our participants are encouraged to tell us immediately if they don't feel comfortable.
Are there any risks associated with receiving TMS?
TMS has a good safety record, and is not believed to have any long-term health effects. The biggest concern for most participants is that at high intensities and high stimulation rates there is a possibility of inducing a seizure akin to those experienced by epileptic patients. There are published safety guidelines about what levels of stimulation are safe, and we adhere to these guidelines closely. We discuss the risks associated with TMS with our participants, and we ask a series of questions to make sure that these risks are not elevated for them.
Should I participate in a TMS study?
TMS is generally safe, but there are some people who should never have TMS, and there are some people who should only have it in special cases where there is a potential benefit for them, like a clinical trial. We will generally not test you if:
- You have a pacemaker, or any other electronic device inserted in your body
- You have any kind of neurological history, for example a stroke or a serious head injury
- You have epilepsy, or a family history of epilepsy
- You are currently taking prescription medication (with the exception of the contraceptive pill)
- You are pregnant.
What will a TMS study involve?
In a typical experiment, you will be seated in front of a computer doing a straightforward (but sometimes challenging) task. Examples include reacting as fast as possible to lights or sounds, or making judgements about things like whether a weak light has been presented, or how long it was presented for. Before you begin the task, we will apply some pulses of TMS to work out the right strength and location of stimulation for you. During the task, we will apply TMS from time to time to see how it affects your performance.
Experiments may last anywhere from one to three hours. You will have opportunities to take breaks, and you will be paid for your participation at a rate of around £7.50 per hour. We are happy to talk about the purpose of the experiment, although we may withhold some details until afterwards to keep you "naïve". Unfortunately, we cannot pay transport costs.
If you would like to participate in a TMS experiment or have any queries regarding participation, please send an email to:
- or the CNRU lab