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South Korea: Ultrasound System Researchers Succeed in Non-Invasive Deep Brain Stimulation of Mice

Editor: MA Alexander Stark

Conventional methods for stimulating a specific brain region are highly invasive because they have to insert probes into a target brain. A Kaist research team developed a lightweight capacitive micromachined ultrasonic transducer (CMUT) and succeeded in the ultrasound brain stimulation of a freely-moving mouse.

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The miniature transducer for the transcranial ultrasound of a freely-moving mouse.
The miniature transducer for the transcranial ultrasound of a freely-moving mouse.
(Source: Kaist)

Daejeon/South Korea — Although transcranial magnetic stimulation (TMS) and transcranial electrical stimulation (TES) are noninvasive, they have a wide range of stimulation and problems with in-depth stimulation, which makes them problematic for target-specific treatment. Therefore, noninvasive and focused ultrasound stimulation technology is gaining a great deal of attention as a next-generation brain stimulation alternative. Since it is delivered noninvasively, it can be applied safely in humans as well as animal experiments. Focused ultrasound stimulation is more advantageous than conventional methods in terms of providing both local and deep stimulation.

Animal behavior experiments are essential for brain stimulation research; however, ultrasonic brain stimulation technology is currently in the early stages of development. So far, only research outcomes with fixed anesthetized mice have been studied because of the heavy ultrasonic device. Prof. Hyunjoo J. Lee from the School of Electrical Engineering and her team reported a technology that can provide ultrasound stimulation to the brain of a freely-moving mouse through a microminiaturized ultrasound device.

The team studied miniaturization and ultra-lightweight CMUTs through microelectromechanical systems (MEMS) technology and designed a device suitable for behavior experiments. The device weighing less than 1 g (around 0.05 % of the mouse’s weight) has the center frequency, size, focal length, and ultrasonic intensity to fit a mouse’s dimensions.

To evaluate the performance of the ultrasonic device, the team stimulated the motor cortex of the mouse brain and observed the movement reaction of its forefoot. They also measured the electromyography (EMG) of the trapezius. As a result, the team confirmed that their ultrasonic device can deliver ultrasound to a depth of 3-4 mm in the mouse brain and stimulate an area of the mouse brain that represents 25 % of its total size.

Based on this research, the team is investigating the effects of ultrasound on sleep by stimulating the brain of sleeping mice. Professor Lee and her team is planning to study mice with diseases, such as Parkinson’s disease, dementia, depression, and epilepsy. She believes that this basic research can contribute to treating human brain-related diseases through ultrasound brain stimulation.

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