Combining Transcranial Magnetic Stimulation with (f)MRI

Transcranial magnetic stimulation (TMS) is a noninvasive and painless tool for the electrical stimulation of the human cortex (Barker et al. 1985). TMS depolarizes cortical neurons and can evoke measurable electrophysiological and behavioral effects. TMS is usually applied to one cortical area, but can also be given to two or more areas (i.e., multi-site TMS). Single or paired stimuli and short stimulus trains (i.e., high-frequency bursts) provide a means of transiently disrupting ongoing neuronal processing in the stimulated cortex. Repetitive TMS (rTMS) refers to the application of prolonged trains of stimuli, which are either given continuously as long trains at a constant rate (continuous rTMS), or intermittently as repetitive bursts (i.e., intermittent or burst-like rTMS). rTMS can modify the excitability of the cerebral cortex at the stimulated site and also at remote interconnected brain regions, beyond the time of stimulation. Its neuromodulatory effects make rTMS a valuable tool to study the functional plasticity of neuronal networks and may be used therapeutically in patients with neurological and psychiatric disorders.