Scientists use magnetic fields to remotely stimulate the brain and control body movements

 Scientists have used magnetic nanoparticles to activate small groups of cells in the brain, which can trigger limb movements, including running, rolling, and loss of control of the limbs, which is an advance in the study and treatment of neurological diseases. Let's follow the editor of Medical Electronics to learn more about the relevant content.

The technique the researchers developed, called magnetic thermal stimulation, gives neuroscientists a powerful tool: a remote, minimally invasive way to trigger activity deep within the brain, switching specific neurons between active and silent states to study what effects those changes have on physiology.

"There's a lot of work going on right now to map the neural pathways that control behavior and emotion," said study leader Arnd Pralle, PhD, a professor in the UB College of Arts and Sciences. "This technology we've developed could help us understand how the computer of our thoughts actually works."

Understanding how the brain works, how the various parts of the organ communicate with each other and control behavior, is key to developing treatments for diseases that involve damage or dysfunction of specific groups of neurons. Traumatic brain injury, Parkinson's disease, dystonia and peripheral paralysis all fall into this category.

The advances reported by Pralle's team could also help scientists seek ways to treat a variety of diseases, such as depression and epilepsy, directly through brain stimulation.

The research was conducted in mice and published in the journal eLife on August 15. Magnetothermal stimulation uses magnetic nanoparticles to stimulate neurons, combined with temperature-sensitive ion channels. When the nanoparticles are heated by an applied magnetic field, brain cells fire, causing the ion channels to open.

Targeting highly specific brain regions

Green areas are targeted cells in the striatum.

In mice, Pralle's team successfully activated three areas of the brain, inducing specific motor functions.

Stimulating cells in the motor cortex caused the mice to run, while stimulating cells in the striatum caused them to circle. When the scientists activated areas deeper in the brain, the mice froze in motion, unable to move their limbs.

"With our method, we can target a very small group of cells, an area of ​​about 100 microns, about the width of a human hair," Pralle said.

How does magnetic thermal stimulation work?

Magnetothermal stimulation allows researchers to activate individual neurons in the brain using heated magnetic nanoparticles.

How does it work? First, scientists use genetic engineering to induce a specific DNA strand to target neurons, allowing these cells to produce heat-activated ion channels. Then, the researchers inject specially made magnetic nanoparticles into the same area of ​​the brain. These nanoparticles lock onto the surface of the target neurons, forming a thin covering like onion skin.

The nanoparticles used by the researchers in this study have a structure in which a manganese-iron composite shell surrounds a cobalt-iron composite magnetic core.

When an external alternating magnetic field is applied to the brain, it causes the magnetic nanoparticles to flip rapidly, generating heat that warms the targeted cells. This forces temperature-sensitive ion channels to open, stimulating neurons to fire.

Beyond other methods such as optogenetics

Pralle has been working on advancing magnetothermal stimulation for a decade, initially demonstrating the technique's effectiveness in activating neurons in a dish and then in controlling the behavior of a tiny nematode worm.

Magnetic thermal stimulation has some advantages over other deep-brain stimulation methods, Pralle said.

One of the best-known techniques, optogenetics, uses light instead of magnetic heating to activate cells. But optogenetics usually requires implanting tiny fiber-optic cables in the brain, while magnetic heat stimulation can be done remotely and is less invasive, Pralle said. Even after the mice's brains were stimulated several times, the targeted neurons showed no signs of damage, he added.

The next step in the research is to use magnetic thermal stimulation to activate and silence different areas of the mouse brain at the same time. Pralle is working with Polina Anikeeva, PhD, a researcher at MIT and Harvard Medical School, to advance this project. We expect that this minimally invasive method will enable more precise control of brain activity and bring hope for the treatment of a variety of brain-related diseases.

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