Neuromodulatory transcranial magnetic stimulation (TMS) changes functional connectivity proportional to the electric-field induced by the TMS pulse

• Published in: Clinical neurophysiology Vol. 165; pp. 16 - 25
• Main Authors: Balderston, Nicholas L., Duprat, Romain J., Long, Hannah, Scully, Morgan, Deluisi, Joseph A., Figueroa-Gonzalez, Almaris, Teferi, Marta, Sheline, Yvette I., Oathes, Desmond J.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.09.2024
• Subjects: Adult; Electric-field modeling; Female; fMRI; Functional connectivity; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Motor Cortex - diagnostic imaging; Motor Cortex - physiology; Nerve Net - diagnostic imaging; Nerve Net - physiology; Neurology; Neuronavigation; Prefrontal Cortex - diagnostic imaging; Prefrontal Cortex - physiology; Theta burst stimulation; TMS; Transcranial Magnetic Stimulation - methods; Functional connectivity; Electric-field modeling; Theta burst stimulation; fMRI; TMS; Neuronavigation
• ISSN: 1388-2457; 1872-8952; 1872-8952
• DOI: 10.1016/j.clinph.2024.06.007

•TMS changes resting state functional connectivity proportional to the electric field distribution of the TMS pulse.•Results offer critical insight into the mechanism underlying TMS modulation of brain connectivity.•They also show that a generalized connectivity mapping approach may inform precision targeting efforts. Transcranial magnetic stimulation (TMS) can efficiently and robustly modulate synaptic plasticity, but little is known about how TMS affects functional connectivity (rs-fMRI). Accordingly, this project characterized TMS-induced rsFC changes in depressed patients who received 3 days of left prefrontal intermittent theta burst stimulation (iTBS). rs-fMRI was collected from 16 subjects before and after iTBS. Correlation matrices were constructed from the cleaned rs-fMRI data. Electric-field models were conducted and used to predict pre-post changes in rs-fMRI. Site by orientation heatmaps were created for vectors centered on the stimulation site and a control site (contralateral motor cortex). For the stimulation site, there was a clear relationship between both site and coil orientation, and connectivity changes. As distance from the stimulation site increased, prediction accuracy decreased. Similarly, as eccentricity from the optimal orientation increased, prediction accuracy decreased. The systematic effects described above were not apparent in the heatmap centered on the control site. These results suggest that rs-fMRI following iTBS changes systematically as a function of the distribution of electrical energy delivered from the TMS pulse, as represented by the e-field model. This finding lays the groundwork for future studies to individualize TMS targeting based on how predicted rs-fMRI changes might impact psychiatric symptoms.