Repetitive transcranial magnetic stimulation as a neuropsychiatric tool: Present status and future potential

Repetitive transcranial magnetic stimulation (rTMS) has emerged as a promis ing therapeutic intervention in the treatment of affective disorders. The d ifferences in the type of electrical stimulation required for therapeutic e fficacy by rTMS and electroconvulsive therapy (ECT) are discussed. In contr ast to ECT, rTMS would not appear to require the generation of a major moto r seizure to achieve therapeutic efficacy. Accordingly, it carries the pote ntially important clinical advantages of not requiring anesthesia and of av oiding side effects such as transient memory loss. Preclinical studies on l ong-term potentiation (LTP) and long-term depression (LTD) in hippocampal a nd amygdala slices, as well as clinical data from neuroimaging studies, hav e provided encouraging clues for potential frequency-dependent effects of r TMS. Preliminary evidence from positron emission tomography (PET) scans sug gests that higher frequency (20 Hz) stimulation may increase brain glucose metabolism in a transsynaptic fashion, whereas lower frequency (1 Hz) stimu lation may decrease it. Therefore, the ability of rTMS to control the frequ ency as well as the location of stimulation, in addition to its other advan tages, has opened up new possibilities for clinical explorations and treatm ents of neuropsychiatric conditions.