Intra- and Interindividual Moderators of Prefrontal Excitability Investigated Using Simultaneous TMS With Neuroimaging

The simultaneous application of brain stimulation and neuroimaging offers significant potential for advancing basic neuroscience research and developing objective diagnostic and prognostic markers for mental disorders. The University Research Facility in Behavioral and Systems Neuroscience (UBSN), in collaboration with Principal Investigator Dr. Georg Kranz, recently acquired a TMS-compatible Magnetic Resonance Imaging (MRI) radio-frequency head coil. This cutting-edge equipment, developed by Dr. Martin Tik's research lab in Vienna, enables detailed mapping of both local and remote neural effects of intermittent theta-burst stimulation (iTBS)-a non-pharmacological treatment with proven efficacy for mental disorders. The upgraded setup addresses limitations of older concurrent TMS-fMRI systems, which struggled with image quality and practical applicability. The new system incorporates a multi-channel receiver array, allowing for high-resolution imaging at a fast rate. In this design, the TMS coil is positioned outside the imaging coil, with stimulation pulses passing through the thin imaging coil to reach the participant's brain and induce targeted neural changes. This advanced system enables the investigation of therapeutic network changes induced by iTBS by capturing acute brain responses during stimulation. Additionally, its sensitivity allows for dose-response assessments at the individual subject level. To leverage these advancements, pilot studies utilizing concurrent rTMS/fMRI are proposed to investigate intra- and interindividual moderators of therapeutic brain stimulation. The iTBS/fMRI study will focus on stimulation-induced hemodynamic changes in key subcortical structures and networks that mediate therapeutic responses to iTBS. Specifically, the study aims to examine changes in central limbic regions, including the subgenual anterior cingulate cortex (sgACC), anterior insula, amygdala, ventromedial prefrontal cortex, and orbitofrontal cortex. By exploring these regions, the mechanisms underlying the therapeutic effects of rTMS can be elucidated, providing a comprehensive understanding of how acute brain responses translate into clinical outcomes. This approach represents a significant step forward in advancing the understanding of iTBS, with the potential to refine and optimize this treatment for mental disorders.