Transcranial magnetic stimulation (TMS) is the use of powerful rapidly changing magnetic fields to induce electric fields in the brain by electromagnetic induction without the need for surgery or external electrodes.
TMS was originally developed as a tool in brain research, and has been used to stimulate or suppress brain activity in experiments on human subjects.
TMS is currently under study as a treatment for severe depression and auditory hallucinations. It is particularly interesting as it may provide an viable treatment to certain aspects of drug resistant mental illness, particularly as an alternative to electroconvulsive therapy. TMS is also under investigation for the treatment of drug-resistant epilepsy.
When properly combined with MRI and EEG, TMS becomes a brain mapping tool. By stimulating different points of the cortex and recording responses, e.g., from muscles, one may obtain maps of functional brain areas. By measuring EEG, one may obtain information about the healthiness of the cortex (its reaction to TMS) and about area-to-area connections.
Although research in this area is in its infancy, there is now strong evidence that TMS is an effective treatment for both depression and auditory hallucinations, with more symptoms and disorders being researched.
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