Non-invasive Deep Brain Stimulation using Electromagnetic Waves.

This paper presents the novel study of deep brain stimulation using electromagnetic waves. Using giga-hertz electric fields, we can manipulate both amplitudes and phases to achieve focal stimulation at target regions inside the brain tissue. However, the issue with this approach would be that neurons have priorly been shown to respond to lower frequency electric fields (similar to 1kHz). To overcome this issue, similar to the recently proposed temporal interference stimulation for electric currents, we propose using two giga-hertz electromagnetic waves differing from each other by a small frequency offset to potentially modulate neurons for non-invasive deep brain stimulation purposes. Moreover, leveraging the advances in antenna technology, we can create miniature antenna arrays at giga-hertz that can be endocranially implanted to allow for continuous operation, which can also help mitigate signal attenuation. To achieve high focality, we then propose an optimization framework that optimizes the antenna array phases and amplitudes to achieve focal stimulation at multiple target regions inside the brain tissue without moving the antenna arrays. We test the efficacy of our proposed method via Finite Element Method simulations on four realistic 2D human brain phantoms. Our results show that with endocranially implanted array size of mean 4.6cm consisting of point source antenna array elements, a focality of mean 3cm can be achieved at targets deep inside the brain tissue.