INTRACORTICAL MICROMAGNETIC STIMULATION FOR TARGETED NEURONAL INHIBITION AND SEIZURE SUPPRESSION

Intracortical micromagnetic stimulation (μMS) presents a novel approach to therapeutic neuromodulation. μMS delivered by MEMS-based implantable micro-coils uses time-varying magnetic fields that induce spatially asymmetrical electric fields localized near the probe tip, enabling targeted and precise neural modulation.^[1] Custom micro-coil designs were developed to enable in vivo two-photon microscopy (TPM) and wide-field imaging for both cellular and population levels and were implanted in the visual cortex of transgenic mice expressing the genetically encoded green fluorescent calcium indicator, GCaMP8f (Fig.1A,B). TPM revealed that single-neuron responses to μMS exhibited robust and consistent suppression (n=12/14), with the magnitude of suppression increasing with stimulation intensity. The proportion of suppressed cells was 14% at low stimulation intensity, and increased to 23% at medium and 41% at high intensities, respectively (Fig.1C). Among μMS-responsive neurons, neither soma diameter (excitatory pyramidal neurons are known to have larger somas than inhibitory interneurons^[2]) nor distance from the electrode location influenced response type, indicating a larger fraction was significantly suppressed, including both excitatory and inhibitory cell types (Fig.1D). Comparative dual-probe stimulation using μMS and μES (which typically induces neuronal activation) revealed that μMS elicited faster and stronger somatic responses, and could neutralize μES-induced excitation (Fig.1E). We further investigated μMS suppression of neuronal hyperactivity under pathological conditions by chemically inducing seizures through topical application of bicuculline (100 μM) to V1, resulting in strong neural bursts every 5-20s. Application of μMS immediately before these bursts reduced response magnitude by up to 54%, particularly in the regions of interest closer to the micro-coils (Fig.1F).^[3]