Towards a High-Resolution, Implantable Neural Interface

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DARPA has awarded contracts to five research organizations and one company that will support the Neural Engineering System Design (NESD) program: Brown University; Columbia University; Fondation Voir et Entendre (The Seeing and Hearing Foundation); John B. Pierce Laboratory; Paradromics, Inc.; and the University of California, Berkeley. These organizations have formed teams to develop the fundamental research and component technologies required to pursue the NESD vision of a high-resolution neural interface and integrate them to create and demonstrate working systems able to support potential future therapies for sensory restoration. Four of the teams will focus on vision and two will focus on aspects of hearing and speech.

DARPA announced NESD in January 2016 with the goal of developing an implantable system able to provide precision communication between the brain and the digital world. Such an interface would convert the electrochemical signaling used by neurons in the brain into the ones and zeros that constitute the language of information technology, and do so at far greater scale than is currently possible. The work has the potential to significantly advance scientists' understanding of the neural underpinnings of vision, hearing, and speech and could eventually lead to new treatments for people living with sensory deficits.

“The NESD program looks ahead to a future in which advanced neural devices offer improved fidelity, resolution, and precision sensory interface for therapeutic applications,” said Phillip Alvelda, the founding NESD Program Manager. “By increasing the capacity of advanced neural interfaces to engage more than one million neurons in parallel, NESD aims to enable rich two-way communication with the brain at a scale that will help deepen our understanding of that organ’s underlying biology, complexity, and function.”

Although the goal of communicating with one million neurons sounds lofty, Alvelda noted, “A million neurons represents a miniscule percentage of the 86 billion neurons in the human brain. Its deeper complexities are going to remain a mystery for some time to come. But if we’re successful in delivering rich sensory signals directly to the brain, NESD will lay a broad foundation for new neurological therapies.”

The program’s first year will focus on making fundamental breakthroughs in hardware, software, and neuroscience, and testing those advances in animals and cultured cells. Phase II of the program calls for ongoing basic studies, along with progress in miniaturization and integration, with attention to possible pathways to regulatory approval for human safety testing of newly developed devices. As part of that effort, researchers will cooperate with the U.S. Food and Drug Administration (FDA) to begin exploration of issues such as long-term safety, privacy, information security, compatibility with other devices, and the numerous other aspects regulators consider as they evaluate potential applications of new technologies.

The NESD call for proposals laid out a series of specific technical goals, including development of an implantable package that accounts for power, communications, and biocompatibility concerns. Part of the fundamental research challenge will be developing a deep understanding of how the brain processes hearing, speech, and vision simultaneously with individual neuron-level precision and at a scale sufficient to represent detailed imagery and sound. The selected teams will apply insights into those biological processes to the development of strategies for interpreting neuronal activity quickly and with minimal power and computational resources.

“Significant technical challenges lie ahead, but the teams we assembled have formulated feasible plans to deliver coordinated breakthroughs across a range of disciplines and integrate those efforts into end-to-end systems,” Alvelda said.

Among the many disciplines represented in the teams are neuroscience, low-power electronics, photonics, medical device packaging and manufacturing, systems engineering, mathematics, computer science, and wireless communications. In addition to overcoming engineering-oriented hardware, biocompatibility, and communication challenges, the teams must also develop advanced mathematical and neuro-computation techniques to decode and encode neural data and compress those troves of information so they are tractable within the available bandwidth and power constraints.

The teams’ approaches include a mix of fundamental research and applied science and engineering. The teams will either pursue development and integration of complete NESD systems, or advance particular aspects of the research, engineering, and mathematics required to achieve the NESD vision, providing new tools, capabilities, and understanding. Summaries of the teams’ proposed research appear below; for additional details, refer to the NESD factsheet.

A Brown University team led by Dr. Arto Nurmikko will seek to decode neural processing of speech, focusing on the tone and vocalization aspects of auditory perception. The team’s proposed interface would be composed of networks of up to 100,000 untethered, submillimeter-sized “neurograin” sensors implanted onto or into the cerebral cortex. A separate RF unit worn or implanted as a flexible electronic patch would passively power the neurograins and serve as the hub for relaying data to and from an external command center that transcodes and processes neural and digital signals.

A Columbia University team led by Dr. Ken Shepard will study vision and aims to develop a non-penetrating bioelectric interface to the visual cortex. The team envisions layering over the cortex a single, flexible complementary metal-oxide semiconductor (CMOS) integrated circuit containing an integrated electrode array. A relay station transceiver worn on the head would wirelessly power and communicate with the implanted device.

A Fondation Voir et Entendre team led by Drs. Jose-Alain Sahel and Serge Picaud will study vision. The team aims to apply techniques from the field of optogenetics to enable communication between neurons in the visual cortex and a camera-based, high-definition artificial retina worn over the eyes, facilitated by a system of implanted electronics and micro-LED optical technology.

A John B. Pierce Laboratory team led by Dr. Vincent Pieribone will study vision. The team will pursue an interface system in which modified neurons capable of bioluminescence and responsive to optogenetic stimulation communicate with an all-optical prosthesis for the visual cortex.

A Paradromics, Inc., team led by Dr. Matthew Angle aims to create a high-data-rate cortical interface using large arrays of penetrating microwire electrodes for high-resolution recording and stimulation of neurons. As part of the NESD program, the team will seek to build an implantable device to support speech restoration. Paradromics’ microwire array technology exploits the reliability of traditional wire electrodes, but by bonding these wires to specialized CMOS electronics the team seeks to overcome the scalability and bandwidth limitations of previous approaches using wire electrodes.

A University of California, Berkeley, team led by Dr. Ehud Isacoff aims to develop a novel “light field” holographic microscope that can detect and modulate the activity of up to a million neurons in the cerebral cortex. The team will attempt to create quantitative encoding models to predict the responses of neurons to external visual and tactile stimuli, and then apply those predictions to structure photo-stimulation patterns that elicit sensory percepts in the visual or somatosensory cortices, where the device could replace lost vision or serve as a brain-machine interface for control of an artificial limb.

DARPA structured the NESD program to facilitate commercial transition of successful technologies. Key to ensuring a smooth path to practical applications, teams will have access to design assistance, rapid prototyping, and fabrication services provided by industry partners whose participation as facilitators was organized by DARPA and who will operate as sub-contractors to the teams.

“DARPA has been a pioneer in brain-machine interface technology since the 1970s, but we began investing heavily in the early 2000s when the confluence of improved sensing and information technology opened the door to new capabilities,” said Justin Sanchez, Director of DARPA’s Biological Technologies Office. “Since then, DARPA has invested hundreds of millions of dollars transitioning ‘neuroscience’ into ‘neurotechnology’ with a series of cumulatively more advanced research programs that expand the frontiers of what is possible in this enormously difficult domain. We’ve laid the groundwork for a future in which advanced brain interface technologies will transform how people live and work, and the Agency will continue to operate at the forward edge of this space to understand how national security might be affected as new players and even more powerful technologies emerge.”

DARPA is committed to exploring the ethical, legal, and societal implications of potential, future human applications of NESD technologies. Toward that end, the Agency has ongoing engagement with several experts in biomedical ethics to ensure that NESD and related neurotechnology efforts maximize societal value and minimize potential risks. DARPA also encourages publication of NESD fundamental research results to help inform broader conversations about technology and society.


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