Using optogenetics— a biological technique that involves the use of light to control cells in living tissue— a team from the University of Arizona has created a new system to turn specific neuron groups in the brain on or off, an innovation that could lead to reduced symptoms for those with neurological disorders, improved movement in paralyzed individuals and the ability to turn off areas of the brain that cause pain.
These new systems are fully implantable, wireless and battery free optoelectronic devices , which allow multimodal operation in neuroscience research.
“We're making these tools to understand how different parts of the brain work,” University of Arizona biomedical engineering professor Philipp Gutruf said in a statement. “The advantage with optogenetics is that you have cell specificity: You can target specific groups of neurons and investigate their function and relation in the context of the whole brain.”
In optogenetics, researchers load specific neurons with opsins, proteins that convert light to electrical potentials that make up the function of a neuron. Researchers can activate only the opsin-loaded neurons when they shine light on an area of the brain.
Early methods of optogenetics involve sending light to the brain through optical fibers. This meant that test subjects were physically tethered to a control station.
Other researchers developed battery-free options but those were often bulky and had to be attached visibly outside the skull. This method did not allow for precise control of the light’s frequency or intensity and only allowed one area of the brain to be stimulated at a time.
“With this research, we went two to three steps further,” Gutruf said. “We were able to implement digital control over intensity and frequency of the light being emitted, and the devices are very miniaturized, so they can be implanted under the scalp.
“We can also independently stimulate multiple places in the brain of the same subject, which also wasn't possible before,” he added.
The ability to control how intense the light is will allow researchers to control exactly how much of the brain the light is affecting. For example, the brighter the light, the farther it will reach.
Controlling the light’s intensity also means controlling the heat generated by light sources and ultimately avoiding the accidental activation of neurons that are activated by heat.
The new implants, which do not cause any adverse effects in subjects and do not degrade over time, are not significantly larger or heavier than past iterations and are powered by external oscillating magnetic fields. They are also designed in a way where the signal will remain strong in most circumstances.
“This system has two antennas in one enclosure, which we switch the signal back and forth very rapidly so we can power the implant at any orientation,” Gutruf said. “In the future, this technique could provide battery-free implants that provide uninterrupted stimulation without the need to remove or replace the device, resulting in less invasive procedures than current pacemaker or stimulation techniques.”
These devices are implanted with a surgical procedure where a patient is fitted with a neurostimulator. The researchers demonstrated that they could implant the devices safely into animals and image using computer tomography and magnetic resonance imaging to enable even greater insight into clinically relevant parameters like the state of bone and tissue and the placement of the device.
The study was published in Nature Electronics.