Design of Submillimeter Magnetic Stimulation Instrumentation and Its Targeted Inhibitory Effect on Rat Model of Epilepsy

Although repetitive transcranial magnetic stimulation (rTMS) is a powerful tool for suppressing seizures, it is limited by its large coils and lower spatial resolution, thus making the targeting mechanism of the inhibitory effect unclear. Therefore, we studied whether smaller magnetic stimulation instrumentation can replace rTMS to achieve targeted suppression of epilepsy. In this study, the epilepsy model was first induced in hippocampal slices from eight-day-old rats by low-magnesium solution and recorded by a microelectrode array in vitro . We designed a smaller submillimeter inductor to develop a flexible micromagnetic stimulation ( $\mu $ MS) instrumentation that allows for real-time delivery of electromagnetic fields to hippocampal slices. The biocompatible parylene was used to coat the instrumentation by the chemical vapor deposition process. The impedance was measured before and after the experiment to ensure no current leakage. We also designed the peripheral driving circuit and interface of the magnetic stimulation instrumentation. When we placed the $\mu $ MS in the CA3b subregion of the hippocampal slices, the epileptiform discharges were completely inhibited, while they were not affected when we placed the $\mu $ MS in the dentate gyrus subregion. These results proved that the submillimeter $\mu $ MS instrumentation, as a new type of neural regulatory sensor, can suppress epilepsy activity.