Abstract :
Functional neuroimaging with PET, SPECT, and fMRI has allowed important insights into the brain regions that are important in a variety of neuropsychiatric diseases. However, apart from surgery, there has been no way to translate this new-found neuroanatomical knowledge into therapy. Recently a new technology, transcranial magnetic stimulation (TMS), has been refined. TMS involves rapidly passing an electrical current through a coiled wire and creating a powerful, localized and transient magnetic field. When placed on the scalp, this magnetic field proceeds unimpeded through the skull and soft tissues, depolarizing superficial cortical neurons. Rapid stimulation (rTMS) can continuously fire a group of neurons, making them metabolically active yet unavailable for communication with other neurons. This produces a transient ‘functional lesion.’ TMS can thus augment other forms of neuroimaging to map brain-behavior relationships. It has been used to investigate vision, language, movement, memory and mood. rTMS has also been shown to transiently improve reaction time in Parkinsonʹs Disease. Further, several groups have now begun to investigate whether prefrontal rTMS might be used as a potential treatment for depression. By combining rTMS with functional neuroimaging, and expanding on knowledge that stimulation at different frequencies can have widely divergent and in fact opposite effects on neurons, rTMS may prove to be a valuable tool in understanding, and potentially treating, a wide variety of neuropsychiatric diseases - from epilepsy and dementia to depression and OCD.
