Abstract
Tourette Syndrome (TS) is associated with motor and vocal tics, emotional and behavioral problems, and diminished quality of life. Inhibitory transcranial magnetic stimulation (TMS) of the Supplementary Motor Area (SMA) has been associated with reduced tic severity. Previous research has shown that there is individual variation in resting state and task evoked brain networks. Additionally, electric field distributions generated by TMS via the finite element method (FEM) method SimNIBS also show inter-individual differences. Due to this variation in structure and function, a pipeline was developed to incorporate individual functional and electric field distributions to find an individualized TMS target within SMA for a clinical trial in 12-21 year olds with TS. To implement this pipeline, anatomical and bilateral finger tapping task evoked functional MR images were collected from N = 23 youth with tics. The images were preprocessed using the ABCD-HCP pipeline. First-level analyses were performed on the preprocessed finger tapping images to produce statistical parametric maps (SPMs) per participant. Using a native space SMA mask, the SPMs were constrained to just activation within SMA. Separately, a 5x5 grid of equally spaced coordinates across SMA was produced per participant to have a set of 25 candidate TMS targets. SimNIBS was run 25 times – once per candidate target – to model the expected induced electric field on the cortex. Like the SPMs, the induced electric field maps were constrained to just SMA. Correlations between the SPMs and modeled electric field were calculated for each of the 25 grid coordinates. The coordinate with the highest correlation was selected as the target for TMS treatment sessions. Using euclidean distance, preliminary results show high variability in target selection across participants. Results support method feasibility and utility of quantitative methods to inform personalized TMS target selection that accounts for individual differences in brain anatomy and function.