Measures of hippocampus connectivity as predictors of Theta Burst Stimulation response

Poster Session F - Tuesday, April 16, 2024, 8:00 – 10:00 am EDT, Sheraton Hall ABC

Andre Cornejo Marin^1,2,3 (andre.cornejo@mail.utoronto.ca), Chaim Katz^1,2,3,4, Ivan Skelin^1,3, Taufik Valiante^1,2,3,5,6; ¹Krembil Brain Institute, Toronto Western Hospital (TWH), ²University of Toronto, ³Center for Advancing Neurotechnological Innovation to Application (CRANIA), ⁴University of Calgary, ⁵The KITE Research Institute, University Health Network, ⁶Department of Neurosurgery, University Health Network

Theta Burst Stimulation (TBS) has been proposed as a therapeutic tool aimed to modulate different maladaptive aspects of behavior. However, the predominant focus of TBS research is on behavioral effects, without sufficient understanding of the underlying mechanisms. This study investigates effective brain connectivity through Corticocortical Evoked Potentials (CCEPs) in response to two stimulation paradigms, Single Pulse Stimulation (SPS) and Theta Burst Stimulation (TBS). CCEPs are characterized by early and late components, reflecting direct and indirect connectivity between the stimulation and target sites. Notably, the root-mean-squared (RMS) voltage of the early component is a marker routinely utilized to assess direct connectivity, previously revealing robust connections between the hippocampus and various cortical regions. We hypothesized that hippocampal connectivity to the limbic system can predict increased theta power persisting post-stimulation, postulated to mediate enhanced plasticity. Through the measurement of RMS voltage of evoked responses following SPS and TBS in stereo-electroencephalography (sEEG) recordings from epilepsy patients, we aim to identify key predictors of the response to electrical stimulation. Preliminary results indicate a significant difference in RMS voltage of evoked responses between the two stimulation modalities –SPS and TBS–, with this difference amplifying with increasing stimulation amplitude. Identification of biomarkers predictive of stimulation response could help pinpointing regions where TBS induces potentially long-lasting plasticity changes.

Topic Area: METHODS: Electrophysiology