Abstract
Transcranial magnetic stimulation (TMS) is a non- invasive technique for stimulating the cerebral cortex and altering cortical and subcortical activities. High- frequency stimulation (10- 20 Hz) has been shown to enhance cortical excitability, and low- frequency stimulation (1 Hz) to inhibit cortical excitability. There are two different approaches in the treatment of depression using TMS : high- frequency stimulation over the left dorsolateral prefrontal cortex (DLPFC) and low- frequency stimulation over the right DLPFC. Brain imaging studies in depression have revealed hypoactivity in the DLPFC and overactivity in the ventromedial prefrontal cortex (VMPFC) including subcallosal area and orbitofrontal cortex. The results of our studies suggest that treatment response to TMS may be correlated with cerebral blood flow (CBF) in the DLPFC and VMPFC, providing the possibility that low- frequency stimulation over the right DLPFC may inhibit overactivity in the VMPFC and high- frequency stimulation over the left DLPFC may enhance hypoactivity in the DLPFC with improvement of depression.
