Non-invasive method for deep brain stimulation

Researchers have developed a non-invasive way to stimulate regions deep within the brain in experiments with mice.

An area in a mouse hippocampus lit up with brain activity.

Credit: Nir Grossman, Suhasa B Kodandaramaiah, Andrii Rudenko

TI stimulation excites an area in a mouse hippocampus.

This new approach, using electrodes placed on the scalp, could offer a safe, less expensive and more accessible therapy for patients with brain diseases such as Parkinson’s or epilepsy.

Deep brain stimulation currently requires electrodes to be implanted near the base of the brain – a complex procedure that carries risks, including brain hemorrhage and infection.

"With the ability to stimulate brain structures non-invasively, we hope that we may help discover new targets for treating brain disorders," says the paper’s lead author, Nir Grossman. He is a former Wellcome-MIT postdoc and current research fellow at Imperial College London.

How the technique works

Two high-frequency electrical currents are generated using electrodes placed on the scalp. The low-frequency electrical activity which occurs where the two currents intersect can stimulate neurons deep in the brain, while the high-frequency current passes through surrounding tissue with no effect. 

By tuning the frequency of the two currents, and changing the number and location of the electrodes, the researchers can control the size and location of the brain tissue that receives the low-frequency stimulation.

This allows them to target locations deep within the brain without affecting any of the surrounding brain structures.

What the research found

The study, part-funded by Wellcome, was led by MIT researchers who tested this technique in mice. They found they could stimulate small regions deep within the brain, including the hippocampus.

They were also able to shift the site of stimulation, allowing them to activate different parts of the motor cortex and prompt the mice to move their limbs, ears, or whiskers.

This study shows for the first time that it is possible to non-invasively stimulate deep regions in the brain without harming any of the surrounding tissue.

In the hippocampus experiments, the technique did not activate the neurons in the cortex, the region lying between the electrodes on the skull and the target deep inside the brain. The researchers also found no harmful effects in any part of the brain. 

Dr Andrew Welchman, Head of Neuroscience and Mental Health at Wellcome, says: "This study is exciting as it provides a proof of principle that less invasive methods can be used for deep brain stimulation.

"The concept of delivering stimulation through intersecting electrical ‘beams’ is well established, but this study demonstrates how this technology can be put into practice. It’s an important step forward towards the goal of a non-invasive treatment for patients with serious neurological diseases."

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