Studies on mechanisms underlying lasting effects of rTMS in monkeys

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PET studies in monkeysGlucose metabolic changes and endogenous dopamine changes were recorded during and after 2000 pulse, 5Hz rTMS with biphasic pulses by using positron emission tomography (PET) in five monkeys. Two main findings were shown. The first is that metabolic changes in the brain continued to be present for at least one week and probably two weeks (Hayashi et al, 2004). This indicates that we can elicit a continuous effect on the brain of patients when we give rTMS once a week or two weeks in the treatment. Another finding is that rTMS evokes dopamine release at basal ganglia (Ohnishi et al, 2004). This suggests that rTMS may be effective for thetreatment of patients with some kinds of movement disorders.Studies on mechanisms for rTMS in humansPET measurements during rTMS over DLPFC showed that it activates the ventral striatum (Ohnishi et al, in press). This means that rTMS over DLPFC must be useful for the treatment of psychiatric disorders. We also studied cerebral blood … More flow (CBF) changes under the magnetic coil using near infrared spectroscopic recordings (NIRS). The results indicate that TMS activation causes a different pattern of CBF changes from those seen in physiological activation or deactivation (Mochizuki et al, in press). This gives us useful information to elucidate which stimulation method is most effective for producing a powerful, lasting effect.rTMS treatment for painrTMS over the motor cortex reduced the degree of acute pain induced by artificial injection, and PET studies during stimulation suggested that TMS reduced the pain by changing the activity of the cingulated cortex (Tamura et a., 2004a). In contrast, the same stimulation may aggravate the chronic pain induced by a special laser stimulator (Tamura et al, 2004b). These results suggest that we should carefully consider which stimulation method is effective for which pain.Monophasic pulses are more powerful for producing a lasting effect than biphasic pulsesMEP enhancement during rTMS was much more drastic when using monophasic pulses than when using biphasic pulses (Arai et al, 2005). The lasting effect after rTMS was also more powerful in monophasic stimulation than biphasic stimulation. We are now considering a new stimulation method which must be more effective than an usual monophasic rTMS.Based on the above results, we try to elucidate a new stimulation method best for the treatment Less