This article, for the first time, presents the design, fabrication, and measurement results of a novel microwave brain stimulation system enabling efficient probe focusing of rectangular-pulse enveloped 6.5-GHz waves. While the conventional ON/OFF stimulation systems in literature employ low frequencies below 0.5 GHz, the proposed system employs 6.5 GHz that can achieve more spatial energy focusing and a moderate level of energy penetration depth. In the proposed system, the ON/OFF modulated microwave signal is generated by a single chip consisting of a voltage-controlled oscillator (VCO) and power amplifier (PA). The VCO is driven by a switch at the current source to generate modulated signals with over 20-dB isolation between the high and low states. The probe with a center-opened aperture surrounded by a symmetric loading enables low power reflection toward the brain and focuses the field in the square-shaped aperture of 1-mm2 area. Finally, it is demonstrated that the 20-min stimulation of an in vivo mouse brain using microwave signals with 1-Hz repetitive pulse envelopes and 1% duty cycle enables the normalized firing rate to reach up to 0.2 while the normalized firing rate stays just within ±0.05 under no stimulation. This suggests that the proposed brain stimulation system can achieve a dramatic change in the activity of individual hippocampal neurons.
|Number of pages||11|
|Journal||IEEE Transactions on Microwave Theory and Techniques|
|State||Published - Sep 2021|
Bibliographical noteFunding Information:
Manuscript received December 23, 2020; revised February 26, 2021; accepted April 3, 2021. Date of publication May 10, 2021; date of current version September 2, 2021. This work was supported in part by the Creative-Pioneering Researchers Program of Seoul National University (SNU), in part by the Brain Research Program through the National Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning under Grant NRF-2015M3C7A1028393, and in part by the Brain Science Research Program under Grant NRF-2015M3C7A1028392 and Grant NRF2018M3C7A1024736. (Corresponding author: Jungsuek Oh.) Seongwoog Oh and Jungsuek Oh are with the Department of Electrical and Computer Engineering (ECE), Institute of New Media and Communications (INMC), Seoul National University, Seoul 151-742, Republic of Korea (e-mail: email@example.com).
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- Brain stimulation system
- Microwave circuits
- Neural probe
- Stimulation system