Study and modulation of human cortical excitability with transcranial magnetic stimulation

Transcranial magnetic stimulation (TMS) can be applied in different paradig ms to obtain a measure of various aspects of cortical excitability. These d ifferent TMS paradigms provide information about different neurotransmitter systems, enhance our understanding about the pathophysiology of neuropsych iatric conditions, and in the future may be helpful as a guide for pharmaco logical interventions. In addition, repetitive TMS (rTMS) modulates cortica l excitability beyond the duration of the rTMS trains themselves. Depending on rTMS parameters, a lasting inhibition or facilitation of cortical excit ability can be induced. These effects can be demonstrated neurophysiologica lly or by combining rTMS with neuroimaging techniques. The effects do not r emain limited to the cortical area directly targeted by rTMS, but affect a wider neural network transynaptically. Modulation of cortical excitability by rTMS may in the future be useful not only as a research tool but also as a therapeutic intervention in neurology, psychiatry, and neurorehabilitati on.