Non-invasive modulation of brain activity and behavior by transcranial radio frequency stimulation

Achieving non-invasive, targeted modulation of deep brain tissue remains a major challenge in neurotechnology. Current non-invasive brain stimulation methods-such as transcranial electrical (TES), magnetic (TMS), and focused ultrasound (TFUS) stimulation-suffer from limitations in spatial focality, penetration depth, or skull-related distortions. Radio frequency (RF) energy, which penetrates biological tissue effectively, offers an alternative avenue for neural modulation. This study introduces Transcranial Radio Frequency Stimulation (TRFS) as a novel, non-invasive neuromodulation technique that leverages RF-induced thermal effects to modulate neural activity in vivo.

We developed a custom RF stimulation system using 945 MHz stub antennas optimized for localized brain heating in mice. Using our unique experimental setup, we developed and tested two operational modes of TRFS:Pristine mode: RF stimulation applied to intact brain tissue.RF-genetics mode: RF stimulation applied to brain regions virally transduced to overexpress the thermosensitive TRPV1 ion channel. Neural activity was recorded using metal-free one-photon fiber photometry with GCaMP calcium indicators. Behavioral effects were assessed through a rotational test in freely moving mice after MK-801-induced hyperlocomotion. Local temperature changes were monitored by optical thermometry.

In pristine mode, RF exposure induced temperature rises leading to dose-dependent suppression of cortical parvalbumin (PV) interneuron activity. This neural suppression translated behaviorally into a unilateral rotational bias ipsilateral to the stimulated hemisphere in hyperlocomotive freely moving mice.In RF-genetics mode, RF stimulation of TRPV1-overexpressing regions produced temperature-dependent excitation of neural activity once local change in temperatures exceeded ΔT ≈ 1.5 °C. Behaviorally, this excitation reversed the direction of rotation in hyperlocomotive freely moving mice, yielding a contralateral bias.

TRFS represents a conceptual advance in neuromodulation, uniting the inherent capability of RF energy to target deep brain tissue with the biophysical reliability of thermal modulation. TRFS applications are bimodal, capable of influencing the pristine brain by suppressing the activity of specific neuronal populations in targeted regions, or of exciting selectively transfected neural ensembles expressing thermosensitive TRPV1 ion channels. The latter modality, first introduced here, represents a novel concept termed "RF-genetics." TRFS represents a promising platform for next-generation non-invasive brain stimulation with potential translational applications in treating various neurological and psychiatric disorders.