Wearable device to record, stimulate brain's dynamic activity with high resolution

A team of researchers from Carnegie Mellon University is starting a project to design and implement a noninvasive neural interface that can be used as a wearable device. This neural interface will be capable of both recording and stimulating the brain's dynamic activity with high temporal and spatial resolution.

The team will receive up to $19.48 million in funding from the Defense Advanced Research Projects Agency (DARPA) through DARPA's "Next-generation Nonsurgical Neurotechnology" (N3) program, which aims to develop high-performance, bidirectional brain-machine interfaces for use by able-bodied individuals. With this funding, the team will work toward a noninvasive neural interface to be worn on the scalp, harnessing novel concepts in physics, biology, and engineering through the use of electricity, ultrasound, and light. The team of researchers is led by Associate Professor Pulkit Grover (ECE), along with Assistant Professor Maysam Chamanzar (ECE) and Assistant Professor Jana Kainerstorfer (BME).

In addition to practical, nonclinical applications for able-bodied individuals, such a novel neural interface could also support more robust research into brain function and dysfunction by providing unprecedented access to neural circuits, and ultimately enable more precise therapeutic interventions to treat neurodegenerative disorders like epilepsy, Alzheimer's, and Parkinson's Disease.

Scientists and engineers consider the human brain to be the body's most complex organ and the world's most complex computational system. This inherent complexity makes the brain a challenge for researchers. Today's most sophisticated neural interfaces require the implantation of electrodes into the brain. Sensing and stimulating neurons at a high resolution is already a challenge with implantable electrodes and attempting to replicate this performance noninvasively through the skull adds another layer of extreme difficulty. Existing noninvasive techniques applied from outside the scalp do not provide sufficient temporal and spatial resolution to support bidirectional neural interfaces for the practical national security applications that DARPA envisions.

Physics dictates that information, and hence, accuracy, is lost when one attempts to sense or stimulate the brain from outside the head. Indeed, there are fundamental information-theoretic limits on the achievable noninvasive accuracy, including some that we have obtained. However, existing systems operate far from these limits. The perspective that our team adopted, which is quite novel, is that instead of fighting the physics that limit our ability to affect the brain noninvasively, we are harnessing those physics in conjunction with the dynamics of the associated biology to radically improve the resolution of neural recording and stimulation."

Associate Professor Pulkit Grover

"Existing methods to interface with the brain with high precision are invasive. On the other hand, noninvasive neural interfacing techniques that are applied from outside the scalp cannot provide high temporal and spatial resolution," says Chamanzar. "One of the most fundamental challenges of almost all existing noninvasive methods is the dispersion of electrical signals and optical or ultrasonic waves as they propagate through the brain tissue."

Half of the project, led by Chamanzar, is aimed at sensing brain function noninvasively. To improve sensing accuracy, the team will use Chamanzar's novel concept of ultrasonic guiding and focusing of light to "pinpoint" light interaction in the brain. The team will pair this enhanced focusing with near-infrared light sensing techniques developed by Kainerstorfer to measure neural activity. Using this, they aim to heighten the efficacy of both techniques and gain higher resolution readings, all while fitting the technology into a wearable "hat" worn on the scalp.

The second half of the project, led by Grover, is aimed at stimulating neurons. At present, neurostimulation is commonly used in treating Parkinson's Disease, epilepsy, and many other neurological disorders, but these treatments require placement of electrodes inside the skull.

"Noninvasive brain stimulation technologies have hardly changed in the last few decades," says Grover. "However, our recent work shows how the nonlinear dynamics of neurons -- properties that make them hard to understand -- can be harnessed to dramatically improve resolution of stimulation over state-of-the-art techniques."

The team aims to provide targeted, localized neuromodulation using novel current waveforms and electrode patch designs developed by Grover, both tailored to exploiting the nonlinear properties of neurons. Chamanzar, who is co-leading the effort, will provide his expertise to tailor the interface design.

"We will construct an array of electrical stimulators in the form of a flexible, wearable device that can be placed over scalp to generate a pattern of electrical signals in the brain by counterbalancing the dispersive effects of brain tissue, scalp and skull," Chamanzar said.

The team will leverage ECE Professor Gary Fedder's expertise in skin-compatible materials to realize this technology in the form of wearable hat, and the expertise of Mellon College of Science biology Professors Alison Barth and Aryn Gittis in experimental validation.

For years, the team has been developing novel theories, technologies, and instrumentations that allow them to sense and stimulate the brain, from diagnosing worsening traumatic brain injuries and concussions, to treating epilepsy and migraines.

Our techniques will make precise neural recording and stimulation technologies accessible to a much larger section of the population. In addition to expanding the benefits of neurotechnology to able-bodied users for nonclinical applications, we look forward to applying our system to the treatment of a broader set of neurological disorders."

Associate Professor Pulkit Grover

"What really excites me about this project is that the technology we are creating might ultimately help identify regions in the brain that are impacted by disease with a much higher resolution than previously possible," Kainerstorfer said. "This work has implications for better diagnosis or localization of epilepsy, traumatic brain injuries, stroke, and other neurological diseases."