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Novel wireless implant successfully simulates nerves

The first wireless and fully implantable device to deliver optogenetics nerve simulation has been created, revolutionizing how light can control the activity of the brain.
A mouse being stimulated by the new device.The mouse’s leg is stimulated by the implantable device, which is powered by the rodent’s own body.
Image credit: Austin Yee

Detailed in the journal Nature Methods, the device is the creation of scientists from the Stanford Bio-X Program, which is affiliated with Stanford University, CA.

Photo of the Remarkables mountain range in Queenstown, New Zealand.

Optogenetics is a relatively new discovery involving the use of light-responsive proteins in the brain. By utilizing light to manipulate neural activity, scientists may turn specific neurons on and off with unprecedented accuracy.

However, it has not proven to be the most practical tool at times.

A fiber optic cable is traditionally required to be attached to the head to ensure light is delivered successfully to the genetically modified brain cell ensembles. This can be a deterrent in mice, as they were unable to navigate small spaces or mazes without interference from the attached cable.

In addition, scientists are tasked with physically handling the mouse prior to the experiment, which is likely to stressthe mouse and deter the animal from its natural behavior.

ImplantSawanAnother challenge facing scientists using optogenetics is how to power the device and track movement. Again, this has traditionally been solved with the use of a bulky device attached to the head – complete with coils and sensors – to locate the mouse and deliver power.

It is these issues that have prevented optogenetics from being used successfully to investigate mental issues, such as stress, depression and anxiety.

A device the size of a peppercorn

Ada Poon, an assistant professor of electrical engineering at Stanford University, successfully developed the miniature device that is the size of a peppercorn.

To power the device, she had the idea of using the mouse’s own body to transfer radio frequency energy that was just the correct wavelength to resonate in a mouse.

Although her initial work on the device was published, she was still unsure how to build a chamber to amplify and store the radio frequency energy.

Teaming up with Yuji Tanabe, a research associate in Poon’s lab, the pair created a final chamber. In its first form, the open chamber would radiate energy in all directions. A honeycomb grid was laid on top of the chamber to counter this, enabling the energy to remain contained inside the chamber.

The grid allows a degree of flexibility. When the mouse paw comes into contact with the grid, it does not receive the full extent of the stored energy below. Instead, the mouse becomes a conduit for the energy because of the exact wavelength that resonates within their body. The power then goes on to be captured by a minuscule 2 mm coil in the device.

The video below demonstrates how the device works:

This new technique allows researchers to successfully power the device and track the mouse’s movements without any restrictions or interference to its natural behavior.

The device is also the first attempt at wireless optogenetics that may be implanted under the skin, paving the way for further research into specific muscles and organs, which may have proven inaccessible before.

Poon describes the discovery as a “new way” of delivering wireless power for optogenetics and says the design of the power source is publicly available for other researchers to use.

The research team hopes the discovery opens the door to new innovative research on mental health disorders, movement disorders and diseases of the internal organs. A grant has already been awarded to the researchers to investigate chronic pain and explore possible new treatments.

Earlier this year, Medical News Today reported how an optogenetics method was used to create an artificial link between unrelated memories in mice.

It is important to stress that optogenetics is only effective on nerves that have been previously prepared to contain light-sensitive proteins. In the lab, this is done by breeding certain mice to contain these proteins or by physically injecting them into a select group of nerves.

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