One potential method for interfering with the neuronal circuitry associated with traumatic memories is through the use of repetitive transcranial magnetic stimulation (rTMS). This technique involves the placement of a cooled electromagnet with a figure-eight coil on the patient's scalp and rapidly turning on and off the magnetic flux. This permits non-invasive, relatively localized stimulation of the surface of the brain (cerebral cortex). The effect of magnetic stimulation varies, depending upon the location, intensity and frequency of the magnetic pulses. Preliminary clinical data shows that low frequency rTMS stimulation leads to a decrease in regional cerebral blood flow.