Low Intensity Multi-Channel Steering TMS Array for Network Level Neuromodulation

Low-intensity transcranial magnetic stimulation (LI-TMS) has been explored as an alternative to transcranial electrical stimulation (tES), but current systems are single-channel and unable to electronically steer the induced electric field. This study introduces a wearable whole-head, multichannel, steerable LI-TMS array. The system features a 102-channel conformal coil array with independently controlled drivers for arbitrary waveform synthesis, alongside a boundary element fast multipole method framework to compute the necessary coil currents for desired cortical field patterns.

A 12-channel prototype was tested using coil-current, electric-field, and thermal measurements. The prototype generated a peak primary electric field of around 1 V/m at a distance of 4 cm from the helmet surface, while whole-array modeling achieved cortical fields up to 1.5 V/m, closely matching a clinically validated low-intensity stimulator (within 3%-5%).

The array demonstrated the capability to focus electric fields on specific regions, such as the dorsolateral prefrontal cortex, while simultaneously delivering fields to nodes within the default mode network. Moreover, it was able to synthesize electric fields following the traveling alpha wave. The research concludes that electronically steerable, whole-head LI-TMS is feasible using affordable microprocessor-controlled power electronics.

This development offers a way to test network-level, phase-locked weak-field neuromodulation without scalp contact or the associated current shunting, paving the way for future applications in this field.