Repetitive transcranial magnetic stimulation activates specific regions inrat brain

Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive techni que to induce electric currents in the brain. Although rTMS is being evalua ted as a possible alternative to electroconvulsive therapy for the treatmen t of refractory depression, little is known about the pattern of activation induced in the brain by rTMS. We have compared immediate early gene expres sion in rat brain after rTMS and electroconvulsive stimulation, a well-esta blished animal model for electroconvulsive therapy. Our result shows that r TMS applied in conditions effective in animal models of depression induces different patterns of immediate-early gene expression than does electroconv ulsive stimulation. In particular, rTMS evokes strong neural responses in t he paraventricular nucleus of the thalamus (PVT) and in other regions invol ved in the regulation of circadian rhythms. The response in PVT is independ ent of the orientation of the stimulation probe relative to the head. Part of this response is likely because of direct activation, as repetitive magn etic stimulation also activates PVT neurons in brain slices.