Considering brain state for individualized functional connectivity-based rTMS

Recent endeavors to optimize the efficacy of repetitive Transcranial Magnetic Stimulation (rTMS) treatment have focused on locating individualized stimulation targets using functional connectivity derived from functional Magnetic Resonance Imaging (fMRI) scans. Practically, this approach involves three main stages: target discovery, target localization, and treatment. As of now, each stage is typically conducted while participants are "at rest", meaning they are not performing a task or being presented with a stimulus. While growing evidence suggests that the effects of TMS are sensitive to the state of the brain at the time of stimulation, brain state has largely been overlooked during the first two stages (target discovery and localization). Here, we consider the potential importance of brain state at each stage of individualized rTMS, reviewing the relevant (and interdisciplinary) literature, and providing some exploratory example cross-state analyses. We also explore how manipulating and constraining brain state with tasks or movie-watching may provide opportunities to improve the reliability of individualized rTMS targets.