News — Traditional implantable medical devices intended for brain stimulation frequently possess a rigidity and bulkiness that is incongruous with one of the human body's most supple and fragile tissues.
In response to this issue, engineers at Rice University have created nanoelectrodes that are minimally invasive and exceptionally flexible. These nanoelectrodes have the potential to function as an implanted platform, enabling long-term, high-resolution stimulation therapy.
As reported in Cell Reports, a study revealed that these minute implantable devices established stable and enduring tissue-electrode interfaces in rodents with minimal scarring or deterioration. The devices were capable of delivering electrical pulses that closely resembled neuronal signaling patterns and amplitudes, surpassing the capabilities of traditional intracortical electrodes.
Due to their exceptional biocompatibility and precise spatiotemporal stimulus control, these devices have the potential to facilitate the advancement of novel brain stimulation therapies. These therapies, such as neuronal prostheses, could greatly benefit individuals with impaired sensory or motor functions.
Lan Luan, a corresponding author on the study and an assistant professor of electrical and computer engineering, explained that the research paper utilizes imaging, behavioral, and histological methods to demonstrate the enhanced effectiveness of stimulation achieved by these tissue-integrated electrodes. The electrodes have the capability to administer precise and minute electrical pulses, thereby facilitating controlled neural activity excitation.
The team of researchers successfully achieved a significant reduction in the required current for neuronal activation, surpassing an order of magnitude. This means that the electrical pulses delivered by the electrodes can be as subtle as a duration of a couple hundred microseconds and an amplitude of one or two microamps. Such precise and low-intensity stimulation holds great potential for advancing the field of brain stimulation therapies.
The recently developed electrode design by the researchers at the Rice Neuroengineering Initiative marks a substantial advancement compared to traditional implantable electrodes utilized for treating conditions like Parkinson's disease, epilepsy, and obsessive-compulsive disorder. Conventional electrodes often lead to adverse tissue reactions and unintended alterations in neural activity. The new electrode design aims to address these challenges and offers a promising solution for enhancing the effectiveness and safety of treatments for such neurological conditions.
Chong Xie, a corresponding author of the study and an associate professor of electrical and computer engineering, stated that traditional electrodes are highly invasive in nature. These electrodes typically activate thousands or even millions of neurons simultaneously.
"When all these neurons are stimulated simultaneously, their individual functions and coordination, which are supposed to follow specific patterns, get disrupted," explained Chong Xie. "While this simultaneous stimulation may have the desired therapeutic effect in certain cases, it lacks the necessary precision and control, especially when it comes to encoding sensory information. To achieve more precise and effective outcomes, greater control over the stimuli is essential."
Xie drew a comparison between the stimulation provided by traditional electrodes and the disruptive impact of "blowing an airhorn in everyone's ear or having a loudspeaker blaring" in a room filled with people. This analogy emphasizes the lack of specificity and precision in conventional electrode stimulation, which can lead to a generalized and disruptive effect on neural activity.
“We used to have this very big loudspeaker, and now everyone has an earpiece,” he said.
Xie drew a comparison between the stimulation provided by traditional electrodes and the disruptive impact of "blowing an airhorn in everyone's ear or having a loudspeaker blaring" in a room filled with people. This analogy emphasizes the lack of specificity and precision in conventional electrode stimulation, which can lead to a generalized and disruptive effect on neural activity.
The capacity to modify the frequency, duration, and intensity of the signals holds the potential for the advancement of innovative sensory prosthetic devices.
Luan stated, "When a larger current is employed, neuron activation becomes more widespread and diffuse. However, we successfully reduced the current and demonstrated a significantly more focused activation. This achievement can pave the way for the development of higher-resolution stimulation devices."
Both Luan and Xie are integral members of the Rice Neuroengineering Initiative, and their respective laboratories are engaged in a collaborative effort to develop an implantable visual prosthetic device aimed at assisting visually impaired patients.
Luan envisions a future where electrode arrays can be implanted to restore impaired sensory function. He highlights that the precision and specificity of neuron activation play a crucial role in generating accurate and precise sensations. Luan emphasizes that the more focused and deliberate the activation of neurons, the higher the level of precision in the generated sensation.
Luan, who will be assuming the position of associate professor starting from July 1, expressed the significance of their electrode's ultraflexible design in achieving enhanced tissue integration. They have published a series of research papers demonstrating the electrode's capability to facilitate improved recording of brain activity over extended periods, yielding superior signal-to-noise ratios.
The study has been led by Roy Lycke, a postdoctoral associate in electrical and computer engineering, and Robin Kim, a graduate student. Both Lycke and Kim have played crucial roles as lead authors in conducting the research.
The National Institute of Neurological Disorders and Stroke (R01NS109361, U01 NS115588) and Rice internal funds supported the research.
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