Repetitive transcranial magnetic stimulation (rTMS) is a tool that enables clinicians and neuroscientists to modulate cortical activity in a non-invasive way. High-frequency rTMS has predominantly an activating effect on the stimulated brain region while low-frequency rTMS has an inhibitory effect. In addition to its usefulness as a research tool and in neurological diagnostics, rTMS may prove useful as a therapeutic option in psychiatry, especially in disorders that are associated with regional changes in cortical activity. For instance, rTMS is under current investigation in the treatment of depression and negative symptoms of schizophrenia. A hypofrontality or a fronto-limbic imbalance associated with both syndromes could be corrected by activating, high frequency rTMS. Conversely, a regional hyperactivity in the temporo-parietal cortex has been described in subjects suffering from auditory hallucinations and tinnitus. Low frequency, inhibitory rTMS is currently evaluated as a therapeutic option in these subjects. In addition to the effects on the directly stimulated brain area, other biological effects of rTMS may exert a beneficial influence on brain function. Amongst these are a modulation of cortico-cortical circuits (e. g. fronto-cingular and fronto-parietotemporal circuits), effects on monoaminergic neuromodulation and neuroendocrine effects. The current knowledge about the therapeutically relevant neurophysiological and neuroendocrine effects of rTMS are reviewed. An improved understanding of the neurophysiological basis of the therapeutic effects of rTMS and of the pathophysiology underlying neuropsychiatric diseases may lead to optimized therapeutic rTMS applications and new clinical indications for rTMS.
Georg Thieme Verlag KG Stuttgart * New York.