Repetitive transcranial magnetic stimulation activates specific regions in rat brain

TLDR

Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive method that induces electric currents in the brain, yet the specific activation patterns it produces remain poorly understood. The study compared immediate early gene expression in rat brains after rTMS versus electroconvulsive stimulation, a well‑established animal model for electroconvulsive therapy. rTMS produced distinct immediate‑early gene expression patterns compared to electroconvulsive stimulation, notably strong activation of the paraventricular nucleus of the thalamus and other circadian‑regulating regions, a response that is orientation‑independent and partly due to direct neuronal activation.

Abstract

Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive technique to induce electric currents in the brain. Although rTMS is being evaluated as a possible alternative to electroconvulsive therapy for the treatment of refractory depression, little is known about the pattern of activation induced in the brain by rTMS. We have compared immediate early gene expression in rat brain after rTMS and electroconvulsive stimulation, a well-established animal model for electroconvulsive therapy. Our result shows that rTMS applied in conditions effective in animal models of depression induces different patterns of immediate-early gene expression than does electroconvulsive stimulation. In particular, rTMS evokes strong neural responses in the paraventricular nucleus of the thalamus (PVT) and in other regions involved in the regulation of circadian rhythms. The response in PVT is independent of the orientation of the stimulation probe relative to the head. Part of this response is likely because of direct activation, as repetitive magnetic stimulation also activates PVT neurons in brain slices.