Anatomical measurements and field modeling to assess transcranial magnetic stimulation motor and non-motor effects

Abstract

Objective

Explore how anatomical measurements and field modeling can be leveraged to improve investigations of transcranial magnetic stimulation (TMS) effects on both motor and non-motor TMS targets.

Methods

TMS motor effects (targeting the primary motor cortex [M1]) were evaluated using the resting motor threshold (rMT), while TMS non-motor effects (targeting the superior temporal gyrus [STG]) were assessed using a pain memory task. Anatomical measurements included scalp-cortex distance (SCD) and cortical thickness (CT), whereas field modeling encompassed the magnitude of the electric field (E) induced by TMS.

Results

Anatomical measurements and field modeling values differed significantly between M1 and STG. For TMS motor effects, rMT was correlated with SCD, CT, and E values at M1 (p < 0.05). No correlations were found between these metrics for the STG and TMS non-motor effects (pain memory; all p-values > 0.05).

Conclusion

Although anatomical measurements and field modeling are closely related to TMS motor effects, their relationship to non-motor effects – such as pain memory – appear to be much more tenuous and complex, highlighting the need for further advancement in our use of TMS and virtual lesion paradigms.