Implantable interface innovation

The NESD program aims to develop technologies that can interact with individual brain neurons.

In April 2013, while President of the United States, Barack Obama launched a research initiative to revolutionize our understanding of the human brain. With a budget of approximately $ 100 million, the Brain Research Initiative’s Innovative Neurotechnologies initiative has sought to develop and apply technologies that examine how the brain records, processes, uses, stores and retrieves information. .

As part of the so-called Grand Challenge, the US Defense Research Agency (DARPA) has launched a series of programs aimed at understanding the dynamic functions of the brain and demonstrating groundbreaking applications based on these results. .

One element is the Neural Engineering System Design (NESD) program announced in January 2016. The goal is to develop an implantable neural interface capable of delivering unprecedented signal resolution and bandwidth between the brain and the world. in a biocompatible device whose volume does not exceed 1 cm3.

One of the goals of the NESD program is to develop a “deep understanding” of how the brain processes hearing, speech and vision simultaneously with the accuracy of individual neurons and to a sufficient extent to represent images and images. detailed sounds.

Dr. Al Emondi of DARPA, currently in charge of the NESD program, explained in more detail. “To be successful, the NESD needs breakthroughs in disciplines such as neuroscience, low-power electronics, photonics, packaging and medical device manufacturing, systems engineering and clinical trials.

In addition to hardware, NESD actors are developing advanced mathematical and neuro-computational techniques to first encode high-definition sensor information between electronic and cortical neural representations, then compress and display them with a loss of precision and accuracy. minimal functionality. ”

DARPA has received orders from five research organizations and one company (see box).

DARPA believes that NESD faces significant technical challenges, but believes that selected teams not only choose viable plans for coordinated breakthroughs in various disciplines, but also integrate them into end-to-end systems.

But this is not a new area of ​​investigation for DARPA. “DARPA has been a pioneer in brain-machine interface technology since the 1970s,” said Justin Sanchez, director of DARPA’s Office of Biological Technologies. “We have laid the groundwork for a future where advanced brain-interface technologies will change the way people live and work, and DARPA will continue to operate at the front of the room.”

Use optogenetics

One of the six projects selected by DARPA will be led by the See and Entender Foundation (FVE), a Paris-based organization that aims to use technology to overcome sensory and visual impairments.

His project, called CorticalSight, will use optogenetic techniques to give the visually impaired a better view. And there are many who could benefit. Estimates suggest that nearly 300 million people suffer from visual impairment. Of these, 40 m are blind and 246 m are visually impaired. There are many reasons why vision is impaired. For some, it is a congenital anomaly, but for others, it is something that develops with age – it is thought that 65% of the visually impaired are 50 years old or older.

CorticalSight will develop a system that will enable communication between a high-resolution, camera-based artificial retina focused on the eyes and neurons of the visual cortex. The project is aimed at those who have lost their eye for a brain connection and will develop a system of implanted electronics and optical technology.

Recognizing the complexity of its objectives, CorticalSight drew on the expertise of the Paris Vision Institute, Chronocam, Gensight, Stanford University, Inscopix and the Friedrich Miescher Institute. The French research center CEA-Leti will also make an important contribution to the development of the active implantable device, which will connect to the visual cortex.

Fabien Sauter-Starace leads the Letis project. He said: “The idea is to develop a brain-computer interface that can restore vision through the stimulation of the visual cortex, and that requires a lot of knowledge.”

In the FVE model, the information would be captured by a camera, then sent to an external device worn on the head and converting images into stimulation patterns. These would then be wirelessly transmitted to a network of high-density micro-LED stimulators for the visual cortex.

In this case, optogenetics will attempt to modify the neurons of the visual cortex to convert certain wavelengths of light into electrical activity. The light received by a camera is calculated to integrate the processing of information from the eye to the brain. The images are then transferred to the implanted LED stimulator, which then activates the neurons.

Sauter-Starace said there were two main options. “They can either stimulate the cortex through electronics, but the more difficult approach is optogenetics, neurons are sensitive to different wavelengths, and it’s about balancing chemical and optical resolutions.”

The “camera” of the FVE project is likely to be a prosthetic eye of the French company Chronocam, recently renamed Prophecy. Sauter-Starace said: “This gives a very good and accurate picture.What we do at Leti is to work on a system to transfer this image to the brain.”

Leti builds on existing technology. “We can use some” technological building blocks, “noted Sauter-Starace. “Others are generated or updated, for example, to increase the data rate.”

At the other end of the system, you need something that can drive a dedicated micro-optical source system. “We use a technology originally developed for microdisplays,” says Sauter-Starace. “We adapt this to the needs of the project by changing the wavelength of the light produced and reducing energy consumption, and we are also facing thermal stress.”

Neuro grains

The Brown University team wants to create a “cortical intranet”. This will involve tens of thousands of wireless micro-devices – each the size of a grain of salt – that can be implanted on or in the cerebral cortex. These implants – neurograins – will function independently and can interact with the brain at each neuron. Neurograins are controlled wirelessly by an electronic patch worn on or under the skin.

“What we are developing is essentially a wireless microarray in the brain that allows us to communicate directly with neurons to an extent previously impossible,” said Professor Arto Nurmikko.

The project will bring many technical challenges, according to Professor Nurmikko. “We have to make the neurograins small enough to be minimally invasive, but with exceptional technical sophistication.” The solution, he says, will require semiconductor technology at the cutting edge of technology. “We also have the challenge of developing the external wireless hub that can simultaneously handle the signals generated by large populations of spatially distributed neurograins.”

While the best brain-computer interfaces of the moment work with about 100 neurons, the team wants to start at 1,000 neurons and build up to 100,000 neurons.

“If you multiply the number of neurons by ten, you will increase the amount of data you need to manage more than that, because the brain works on nested and interconnected circuits,” Nurmikko said. “This is becoming a huge problem with large amounts of data, for which we need to develop new tools for computer neuroscience.”

The six NDSD projects of DARPA

DARPA selected six projects in the first phase of the NESD program.

• Brown University is trying to decode neural processing of speech. The proposed interface would consist of networks of up to 100,000 neurograins.

• Columbia University aims to develop a non-penetrating bioelectrical interface of the visual cortex using a flexible CMOS integrated circuit with an electrode field.

• The View and Entender Foundation aims to use optogenetic techniques to facilitate communication between visual cortex neurons and a camera-based high-resolution artificial retina.

• The John B Pierce laboratory will develop an interface system in which optogenetically modified neurons communicate with a purely optical prosthesis.

• Paradomics aims to use large networks of penetrating micro-wire electrodes to create a high-speed cortical interface for recording and stimulating neurons and for connecting these wires to specialized CMOS electronics.

• The University of California at Berkeley has set a goal to develop a “light field” holographic microscope that detects and modulates the activity of one million neurons in the cerebral cortex and uses photostimulation patterns to replace vision. lost or a brain machine. can interface.

Nanoelectronic silicon

Professor Ken Shepard wants to develop a brain interface device at Columbia University that can change the lives of visually impaired people.

“If we succeed,” he said, “the tiny size and scale of this device could help turn interfaces to the brain, including direct interfaces to the visual cortex, allowing patients who have lost vision to to have complex complexes. ” distinguish models in unprecedented resolutions. ”

According to Professor Shepard, the DARPA project is working on aggressive calendars. “We believe that the only way to achieve this is to adopt a fully electric approach that involves a massive network of surface recordings with more than one million electrodes manufactured as a monolithic device on a single CMOS integrated circuit. our partner foundry together. ”

The implanted chips are adaptable, very light and flexible enough to move with the tissue. “By using advanced silicon nanoelectronics and applying them in an unusual way, we hope to have a major impact on brain-computer interfaces,” said Professor Shepard.

Cortical Modem

Researchers at UC Berkeley’s team call the device they develop a cortical modem – a way to “read” and “write” the brain.

“The ability to talk to the brain has the incredible potential to compensate for the neurological damage caused by degenerative diseases or injuries,” said Professor Ehud Isacoff. “By integrating perceptions into the human cortex, the blind could be allowed to see or feel the paralyzed.”

According to the Berkeley team, reading and writing in neurons requires a two-step device. His reader will be a miniaturized microscope attached to a small window in the skull. The microscope, which can detect up to 1 million neurons at a time, is based on the “light field camera”, which captures light through a series of lenses and reconstructs the images.

For the writing component, the team attempts to project light patterns on neurons using 3D holograms. This stimulates groups of neurons in a way that reflects normal brain activity.

“We do not measure just from a combination of neurons of different types singing different songs,” said Professor Isacoff. “We plan to focus on a subset of neurons that perform some type of function in a particular layer that is spread over a large part of the cortex.” much of the visual or tactile field. ”

A difficult calendar

The NESD program is expected to last four years, with three phases. “The six projects compete,” concludes Sauter-Starace. “We are in the first phase of NESD and maybe the teams will be merged in the future, but currently we are in parallel competition and this is a difficult time.”

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