Neuromodulation using transcranial radio frequency stimulation in rodents
From both research and clinical perspectives, there is a growing need to develop effective, noninvasive stimulation methods of the brain. Existing methods include Transcranial Magnetic Electrical and Ultrasound Stimulation. Each of these methods has advantages and drawbacks. We suggest exploring an alternative approach, radio frequency (RF) stimulation. RF stimulation can penetrate to deep brain structures effectively without direct skin contact. We demonstrate entrainment of neuronal activity, at single cell and neural network levels, by RF exposure in rodent models. We apply RF stimulation at 950 MHz by TEM cell or patch antenna. Our RF stimulation intensities induce electric field and SAR values well below the threshold set by safety regulations. We demonstrate that our stimulation paradigm does not induce a significant increase in the body and brain temperature (<0.5°C; n=4 rats and 4 mice). Using these ‘temperature-safe’ intensities, we record in-vivo brain activity in freely moving rodents with silicon probes (hippocampal and cortical regions) and in head-fixed mice with Ca-imaging. Radio-Frequency stimulation is able to modulate the ongoing activity of neurons, including pyramidal cells and interneurons in both mice and rats. We provide evidence for RF dose- and direction-dependent response in neural firing in head fixed anesthetized rats. Finite-element physics-based simulations demonstrate the possibility of achieving the induction of similar electric field levels to what we have used in our pilot animal studies into the human brain, suggesting the potential use of this novel method in clinical applications.