Flexible nanoelectrodes can provide fine-grained brain stimulation
Engineers' device is gentle on neurons, could serve as sensory prosthesis


Date:
May 30, 2023
Source:
Rice University
Summary:
Engineers have developed ultraflexible implantable nanoelectrodes
that can administer long-term, fine-grained brain stimulation.


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FULL STORY ========================================================================== Conventional implantable medical devices designed for brain stimulation
are often too rigid and bulky for what is one of the body's softest and
most delicate tissues.

To address the problem, Rice University engineers have developed minimally invasive, ultraflexible nanoelectrodes that could serve as an implanted platform for administering long-term, high-resolution stimulation therapy.

According to a study published in Cell Reports, the tiny implantable
devices formed stable, long-lasting and seamless tissue-electrode
interfaces with minimal scarring or degradation in rodents. The devices delivered electrical pulses that match neuronal signaling patterns and amplitudes more closely than stimuli from conventional intracortical electrodes.

The devices' high biocompatibility and precise spatiotemporal stimulus
control could enable the development of new brain stimulation therapies
such as neuronal prostheses for patients with impaired sensory or motor functions.

"This paper uses imaging, behavioral and histological techniques to
show how these tissue-integrated electrodes improve the efficacy of stimulation," said Lan Luan, an assistant professor of electrical and
computer engineering and a corresponding author on the study. "Our
electrode delivers tiny electrical pulses to excite neural activity in
a very controllable manner.

"We were able to reduce the current necessary to elicit neuronal
activation by more than an order of magnitude. Pulses can be as subtle
as a couple hundred microseconds in duration and one or two microamps
in amplitude." The new electrode design developed by researchers in 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 unintended changes in neural activity.

"Conventional electrodes are very invasive," said Chong Xie, an associate professor of electrical and computer engineering and a corresponding
author of the study. "They recruit thousands or even millions of neurons
at a time.

"Each of those neurons is supposed to have their own tune and coordinate
in a specific pattern. But when you shock them all at the same time,
you're basically disrupting their function. In some cases that works fine
for you and has the desired therapeutic effect. But if, for example,
you want to encode sensory information, you need much greater control
over the stimuli." Xie likened stimulation via conventional electrodes
with the disruptive effect of "blowing an airhorn in everyone's ear or
having a loudspeaker blaring" in a roomful of people.

"We used to have this very big loudspeaker, and now everyone has an
earpiece," he said.

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

"Neuron activation is more diffuse if you use a larger current," Luan
said. "We were able to reduce the current and showed that we have a
much more focused activation. This can translate to higher-resolution stimulation devices." Luan and Xie are core members of the Rice Neuroengineering Initiative and their labs are also collaborating on the development of an implantable visual prosthetic device for blind patients.

"Envision one day being able to implant electrode arrays to restore
impaired sensory function: The more focused and deliberate is the
activation of the neurons, the more precise the sensation you're
generating," Luan said.

An earlier iteration of the devices was used to record brain activity.

"We have had a series of publications showing this intimate tissue
integration enabled by our electrode's ultraflexible design really
improves our ability to record brain activity for longer durations and
with better signal-to-noise ratios," said Luan, who has been promoted
to associate professor effective July 1.

Electrical and computer engineering postdoctoral associate Roy Lycke
and graduate student Robin Kim are lead authors on the study.

The National Institute of Neurological Disorders and Stroke (R01NS109361,
U01 NS115588) and Rice internal funds supported the research.

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========================================================================== Story Source: Materials provided by Rice_University. Original written
by Silvia Cernea Clark.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Roy Lycke, Robin Kim, Pavlo Zolotavin, Jon Montes, Yingchu Sun, Aron
Koszeghy, Esra Altun, Brian Noble, Rongkang Yin, Fei He, Nelson
Totah, Chong Xie, Lan Luan. Low-threshold, high-resolution,
chronically stable intracortical microstimulation by
ultraflexible electrodes. Cell Reports, 2023; 42 (6): 112554 DOI:
10.1016/j.celrep.2023.112554 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/05/230530174315.htm

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