Flexible nanoelectrodes can provide subtle brain stimulation

May 30, 2023

(Nanowerk News) Conventional implantable medical devices designed for brain stimulation are often too stiff and bulky for one of the body’s most delicate and delicate tissues.

To address this problem, Rice University engineers have developed a minimally invasive ultraflexible nanoelectrode that can serve as an implantable platform for administering long-term high-resolution stimulation therapy.

According to a study published in Cell Report (“Chronically stable low-threshold, high-resolution, intracortical microstimulation by ultraflexible electrodes”), the small implantable device forms a stable, durable, seamless electrode-tissue interface with minimal scarring or degradation in rodents. The device delivers electrical pulses that match the nerve signaling patterns and amplitudes more closely than stimuli from conventional intracortical electrodes. Two-photon microscopy image of the nanoelectrode (yellow) after two months implanted in a mouse brain, with healthy active neurons (bright area) around the implant. (Image: Rice Neuroengineering Initiative, Rice University)

The device’s high biocompatibility and precise spatiotemporal stimulus control may enable the development of new brain stimulation therapies such as neural prostheses for patients with impaired sensory or motor function.

“This paper uses imaging, behavioral, and histological techniques to demonstrate how these tissue-integrated electrodes enhance the efficacy of stimulation,” said Lan Luan, assistant professor of electrical and computer engineering and corresponding author on the study. “Our electrodes send tiny electrical pulses to excite neural activity in a very controlled way.

“We were able to reduce the current required to elicit neural activation by more than an order of magnitude. The pulses can be as subtle as a few hundred microseconds in duration and one or two microamps in amplitude.

The new electrode design developed by researchers at the Rice Neuroengineering Initiative represents a significant improvement over conventional implantable electrodes used to treat conditions such as Parkinson’s disease, epilepsy, and obsessive-compulsive disorder, which can cause adverse tissue responses and irreversible changes in nerve activity. wanted.

“Conventional electrodes are very invasive,” said Chong Xie, a professor of electrical and computer engineering and co-author of the study. “They recruit thousands or even millions of neurons at once.

“Each of those neurons is supposed to have its own tone and coordination in a certain pattern. But when you electrocute them all at the same time, you’re basically disrupting their functionality. In some cases it may work well for you and have the desired therapeutic effect. But if, for example, you want to encode sensory information, you need much more control over those stimuli.”

Xie likens stimulation via conventional electrodes to distracting effects such as “blowing the air horn in everyone’s ears or making the speakers blaring” in a room full of people.

“Back then we had really big loudspeakers, and now everyone has earpieces,” he says.

The ability to adjust the frequency, duration and intensity of the signal could enable the development of new sensory prosthetic devices.

“The activation of the neurons is more spread out if you use a larger current,” says Luan. “We were able to reduce the flow and show that we have much more focused activation. This could translate into higher resolution stimulation devices.”

Luan and Xie are core members of the Rice Neuroengineering Initiative and their laboratory is also collaborating on the development of implantable visual prosthetic devices for blind patients.

“Imagine one day being able to implant an array of electrodes to restore impaired sensory function: The more focused and deliberate the activation of the neurons, the more precise the sensations you produce,” says Luan.

Previous iterations of the device were used to record brain activity.

“We have had a series of publications (Natural Biomedical Engineering, “Ultra-flexible electrode arrays for months-long high-density electrophysiological mapping of thousands of neurons in rodents”) demonstrated the integration of this intimate network made possible by our electrode’s ultraflexible design actually enhances our ability to record brain activity for longer periods of time and with a better signal-to-noise ratio,” said Luan, who has been promoted to professor association from July 1.

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