Schedule of Events | Symposia

Variability in suprathreshold electric field simulations for transcranial magnetic stimulation treatments

Poster Session D - Monday, March 31, 2025, 8:00 – 10:00 am EDT, Back Bay Ballroom/Republic Ballroom

Megan E. Chang¹ (mec4024@med.cornell.edu), Nicola Manfredi¹, Maximilian Lueckel¹, Megan Johnson¹, Jolin Chou¹, Claire A. Ho¹, Indira Summerville¹, Immanuel G. Elbau¹, Charles J. Lynch¹, Conor Liston¹; ¹Weill Cornell Medicine

Transcranial magnetic stimulation (TMS) is a non-invasive neuromodulation technique used in cognitive neuroscience to establish causality between brain activity and cognitive functions or behaviors (Sandrini et al., 2011). Coil placement and stimulation intensity are crucial for determining whether TMS effectively alters neural activity in targeted brain areas or functional networks. Treatment dosage is typically inferred from motor evoked potentials (MEP), the minimum intensity required to elicit a muscle twitch, and is sometimes adjusted linearly (Stokes et el., 2007). However, this approach assumes uniform responses across individuals, prompting this investigation into whether MEP-based heuristics accurately estimate intensity for effective stimulation. Electric field (E-field) modeling can estimate TMS spatial distribution, considering the distance to cortex, coil type, and brain tissue conductivity derived from cortical segmentation (Thielscher et al., 2015). In this study, we masked motor thresholding E-field simulations utilizing a probabilistic group map of the primary motor cortex (M1) and individual network topologies obtained from precision functional mapping (PFM). The maximum E-field strength within the constrained region established thresholds in treatment E-field simulations, identifying areas of suprathreshold engagement for each subject (n=66). Preliminary results revealed a median suprathreshold stimulated area of 201.87 mm2 (std=875.36 mm2), spanning a range from 0 to 5867.90 mm2. These findings indicate considerable interindividual variability in suprathreshold stimulation, highlighting the limitations of conventional dose calculations which may not adequately capture the complexity of individual brain anatomy and functional connectivity. These findings suggest that E-field-based thresholding approaches for personalized TMS could optimize stimulation accuracy and enhance therapeutic outcomes.

Topic Area: METHODS: Neuroimaging