Whole-Brain Effects of TMS on Intracranial Electrophysiology

This work was advised by Corey Keller in collaboration with the Boes Lab at University of Iowa!

Transcranial magnetic stimulation (TMS) is an FDA-approved technology for psychiatric conditions such as depression that uses magnetic waves to noninvasively modulate regions at the surface of the brain. However, it is not clear what parts of the brain are affected by TMS in humans. Currently existing methods lack spatial or temporal resolution to be able to accurately assess these effects. Here we present the first study in humans using implanted electrodes to directly record the effect of TMS in the brain. We show that this technique is safe in humans. We also demonstrate that TMS as used for depression primarily affects the anterior cingulate cortex within the saliency network, which is responsible for determining the emotional response to pain and negative events. This potentially not only sheds light into the mechanism of TMS, but also validates a potential technology for high resolution mapping of the whole-brain effects of neuromodulation.

Read our pre-print here!

A single representative subject is represented here, which each individual dot representing an electrode implanted in their brain. TMS delivered to the DLPFC (green dot; typically targeted for depression) results in evoked potentials that are specific to TMS delivery (blue dots) instead of sham delivery (orange dots). We call these intracranial TMS-evoked potentials (iTEPs).