Scientists at Rice University have developed a highly flexible nanoelectrode that is designed for long-term implantation in the brain. The brain stimulation provided by the technology is incredibly fine-grained, thanks to the very low current it can deliver. This results in a very discrete area of neurostimulation, potentially allowing for much finer control of small groups of neurons. Pre-existing electrodes tend to be more rigid and larger, potentially causing issues such as tissue damage and scarring if left in place for long periods. However, the new electrode has been shown to remain in place for at least eight months in mice with no scarring or tissue degradation.
Implanting electrodes in the brain can open up completely new avenues of medical endeavor, including brain-machine interfaces that could allow paralyzed patients to communicate, move, and more. However, if a medical device is intended for long-term implantation then it must be an unobtrusive guest in the body, particularly in the very delicate Jell-O-like tissue of the brain.
This latest nanoelectrode can achieve this. Its ultraflexible nature and small size mean that it can slip into brain tissue, and in studies in mice it appears to cause minimal damage or scarring for at least eight months. Moreover, the degree of fine control possible with this electrode is unprecedented – it can stimulate a very small group of neurons, potentially leading to greater efficacy and less noise, which it achieves by delivering a very small electrical current.
“This paper uses imaging, behavioral and histological techniques to show how these tissue-integrated electrodes improve the efficacy of stimulation,” said Lan Luan, a researcher involved in 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 way that neurons communicate under normal circumstances involves millions of tiny connections and highly coordinated signal propagation. Conventional implantable electrodes are somewhat akin to using a sledge-hammer to crack a nut, disrupting this delicate neuronal interplay. This new electrode aims to be much less invasive.
“Conventional electrodes are very invasive,” said Chong Xie, another researcher involved in 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.”
Study in journal Cell Reports: Low-threshold, high-resolution, chronically stable intracortical microstimulation by ultraflexible electrodes
Via: Rice University