Analysis of resting motor threshold, coil-cortex distance and IC3-IC4 functional connectivity in schizophrenia patients during transcranial magnetic stimulation*

Finite element model (FEM) simulations of transcranial magnetic stimulation (TMS) on heterogeneous head models have been conducted to show stimulation strengths within the brain, a comparison between clinical resting motor threshold (RMT) data and simulation data has not been analyzed. We developed anatomically accurate head models of 20 schizophrenia patient using thier MRIs in SimNIBS pipeline. We then utilized FEM software to compute induced electric fields using patient’s clinical parameters during their investigational procedure. In this way, the simulations were based on real patient data and completely customized to each subject. The electric field induced in the brain was recorded and compared with variables such as cortex-coil distance (CCD), age, and RMT. Our results show that there is little to no correlation between the measured CCD at M1 and the clinically-reported RMT or the maximum electric field recorded in the brain after TMS was simulated using Sim4Life. Thus, we hypothesize that the lack of clear correlation between the CCD at M1 and the measured RMT suggests that there are many other variables which may be influencing an individual’s RMT, beyond the CCD.