Transcranial Magnetic Stimulation (TMS)
Non-invasive brain stimulation
Transcranial magnetic stimulation (TMS) is a noninvasive method to modify the activity of specific brain areas. Weak electric currents are induced in the neural tissue via a rapidly changing magnetic field generated by an induction coil. The shape of the coil determines the geometry of the magnetic field, which in turn determines the distribution of activity in underlying brain areas.
TMS has gained importance in cognitive psychology and neurosciences as a unique tool for testing the causal role of specific brain areas. For example, TMS can be used to generate a temporary 'virtual lesion' in a specific are of the cerebral cortex. The functional role of the targeted area can then be assessed with carefully controlled experimental tests of behaviour. Under some circumstances, TMS can also be used to enhance neural processing by increasing the general excitability of a specific brain area. Finally, TMS is also used to probe the functional integrity of pathways linking specific brain areas. Testing the quality of neural pathways is important for some clinical diagnostic purposes, but also in basic research that aims to understand how the brain is "wired-up". We also combine TMS with simultaneous EEG recordings, allowing us to monitor the neural effects of stimulation, and also to explore the connectivity between areas.