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Quadriplegic man reanimates a limb with implanted brain-recording and muscle-stimulating systems

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It took me a few minutes to figure out why this item about a quadriplegic (also known as, tetraplegic) man is news. After all, I have a May 17, 2012 posting which features a video and information about a quadri(tetra)plegic woman who was drinking her first cup of coffee, independently, in many years. The difference is that she was using an external robotic arm and this man is using *his own arm*,

This Case Western Reserve University (CRWU) video accompanies a March 28, 2017 CRWU news release, (h/t ScienceDaily March 28, 2017 news item)

Bill Kochevar grabbed a mug of water, drew it to his lips and drank through the straw.

His motions were slow and deliberate, but then Kochevar hadn’t moved his right arm or hand for eight years.

And it took some practice to reach and grasp just by thinking about it.

Kochevar, who was paralyzed below his shoulders in a bicycling accident, is believed to be the first person with quadriplegia in the world to have arm and hand movements restored with the help of two temporarily implanted technologies.

A brain-computer interface with recording electrodes under his skull, and a functional electrical stimulation (FES) system* activating his arm and hand, reconnect his brain to paralyzed muscles.

Holding a makeshift handle pierced through a dry sponge, Kochevar scratched the side of his nose with the sponge. He scooped forkfuls of mashed potatoes from a bowl—perhaps his top goal—and savored each mouthful.

“For somebody who’s been injured eight years and couldn’t move, being able to move just that little bit is awesome to me,” said Kochevar, 56, of Cleveland. “It’s better than I thought it would be.”

Kochevar is the focal point of research led by Case Western Reserve University, the Cleveland Functional Electrical Stimulation (FES) Center at the Louis Stokes Cleveland VA Medical Center and University Hospitals Cleveland Medical Center (UH). A study of the work was published in the The Lancet March 28 [2017] at 6:30 p.m. U.S. Eastern time.

“He’s really breaking ground for the spinal cord injury community,” said Bob Kirsch, chair of Case Western Reserve’s Department of Biomedical Engineering, executive director of the FES Center and principal investigator (PI) and senior author of the research. “This is a major step toward restoring some independence.”

When asked, people with quadriplegia say their first priority is to scratch an itch, feed themselves or perform other simple functions with their arm and hand, instead of relying on caregivers.

“By taking the brain signals generated when Bill attempts to move, and using them to control the stimulation of his arm and hand, he was able to perform personal functions that were important to him,” said Bolu Ajiboye, assistant professor of biomedical engineering and lead study author.

Technology and training

The research with Kochevar is part of the ongoing BrainGate2* pilot clinical trial being conducted by a consortium of academic and VA institutions assessing the safety and feasibility of the implanted brain-computer interface (BCI) system in people with paralysis. Other investigational BrainGate research has shown that people with paralysis can control a cursor on a computer screen or a robotic arm (braingate.org).

“Every day, most of us take for granted that when we will to move, we can move any part of our body with precision and control in multiple directions and those with traumatic spinal cord injury or any other form of paralysis cannot,” said Benjamin Walter, associate professor of neurology at Case Western Reserve School of Medicine, clinical PI of the Cleveland BrainGate2 trial and medical director of the Deep Brain Stimulation Program at UH Cleveland Medical Center.

“The ultimate hope of any of these individuals is to restore this function,” Walter said. “By restoring the communication of the will to move from the brain directly to the body this work will hopefully begin to restore the hope of millions of paralyzed individuals that someday they will be able to move freely again.”

Jonathan Miller, assistant professor of neurosurgery at Case Western Reserve School of Medicine and director of the Functional and Restorative Neurosurgery Center at UH, led a team of surgeons who implanted two 96-channel electrode arrays—each about the size of a baby aspirin—in Kochevar’s motor cortex, on the surface of the brain.

The arrays record brain signals created when Kochevar imagines movement of his own arm and hand. The brain-computer interface extracts information from the brain signals about what movements he intends to make, then passes the information to command the electrical stimulation system.

To prepare him to use his arm again, Kochevar first learned how to use his brain signals to move a virtual-reality arm on a computer screen.

“He was able to do it within a few minutes,” Kirsch said. “The code was still in his brain.”

As Kochevar’s ability to move the virtual arm improved through four months of training, the researchers believed he would be capable of controlling his own arm and hand.

Miller then led a team that implanted the FES systems’ 36 electrodes that animate muscles in the upper and lower arm.

The BCI decodes the recorded brain signals into the intended movement command, which is then converted by the FES system into patterns of electrical pulses.

The pulses sent through the FES electrodes trigger the muscles controlling Kochevar’s hand, wrist, arm, elbow and shoulder. To overcome gravity that would otherwise prevent him from raising his arm and reaching, Kochevar uses a mobile arm support, which is also under his brain’s control.

New Capabilities

Eight years of muscle atrophy required rehabilitation. The researchers exercised Kochevar’s arm and hand with cyclical electrical stimulation patterns. Over 45 weeks, his strength, range of motion and endurance improved. As he practiced movements, the researchers adjusted stimulation patterns to further his abilities.

Kochevar can make each joint in his right arm move individually. Or, just by thinking about a task such as feeding himself or getting a drink, the muscles are activated in a coordinated fashion.

When asked to describe how he commanded the arm movements, Kochevar told investigators, “I’m making it move without having to really concentrate hard at it…I just think ‘out’…and it goes.”

Kocehvar is fitted with temporarily implanted FES technology that has a track record of reliable use in people. The BCI and FES system together represent early feasibility that gives the research team insights into the potential future benefit of the combined system.

Advances needed to make the combined technology usable outside of a lab are not far from reality, the researchers say. Work is underway to make the brain implant wireless, and the investigators are improving decoding and stimulation patterns needed to make movements more precise. Fully implantable FES systems have already been developed and are also being tested in separate clinical research.

Kochevar welcomes new technology—even if it requires more surgery—that will enable him to move better. “This won’t replace caregivers,” he said. “But, in the long term, people will be able, in a limited way, to do more for themselves.”

There is more about the research in a March 29, 2017 article by Sarah Boseley for The Guardian,

Bill Kochevar, 53, has had electrical implants in the motor cortex of his brain and sensors inserted in his forearm, which allow the muscles of his arm and hand to be stimulated in response to signals from his brain, decoded by computer. After eight years, he is able to drink and feed himself without assistance.

“I think about what I want to do and the system does it for me,” Kochevar told the Guardian. “It’s not a lot of thinking about it. When I want to do something, my brain does what it does.”

The experimental technology, pioneered by the Case Western Reserve University in Cleveland, Ohio, is the first in the world to restore brain-controlled reaching and grasping in a person with complete paralysis.

For now, the process is relatively slow, but the scientists behind the breakthrough say this is proof of concept and that they hope to streamline the technology until it becomes a routine treatment for people with paralysis. In the future, they say, it will also be wireless and the electrical arrays and sensors will all be implanted under the skin and invisible.

A March 28, 2017 Lancet news release on EurekAlert provides a little more technical insight into the research and Kochevar’s efforts,

Although only tested with one participant, the study is a major advance and the first to restore brain-controlled reaching and grasping in a person with complete paralysis. The technology, which is only for experimental use in the USA, circumvents rather than repairs spinal injuries, meaning the participant relies on the device being implanted and switched on to move.

“Our research is at an early stage, but we believe that this neuro-prosthesis could offer individuals with paralysis the possibility of regaining arm and hand functions to perform day-to-day activities, offering them greater independence,” said lead author Dr Bolu Ajiboye, Case Western Reserve University, USA. “So far it has helped a man with tetraplegia to reach and grasp, meaning he could feed himself and drink. With further development, we believe the technology could give more accurate control, allowing a wider range of actions, which could begin to transform the lives of people living with paralysis.” [1]

…

Previous research has used similar elements of the neuro-prosthesis. For example, a brain-computer interface linked to electrodes on the skin has helped a person with less severe paralysis open and close his hand, while other studies have allowed participants to control a robotic arm using their brain signals. However, this is the first to restore reaching and grasping via the system in a person with a chronic spinal cord injury.

In this study, a 53 year-old man who had been paralysed below the shoulders for eight years underwent surgery to have the neuro-prosthesis fitted.

This involved brain surgery to place sensors in the motor cortex area of his brain responsible for hand movement – creating a brain-computer interface that learnt which movements his brain signals were instructing for. This initial stage took four months and included training using a virtual reality arm.

He then underwent another procedure placing 36 muscle stimulating electrodes into his upper and lower arm, including four that helped restore finger and thumb, wrist, elbow and shoulder movements. These were switched on 17 days after the procedure, and began stimulating the muscles for eight hours a week over 18 weeks to improve strength, movement and reduce muscle fatigue.

The researchers then wired the brain-computer interface to the electrical stimulators in his arm, using a decoder (mathematical algorithm) to translate his brain signals into commands for the electrodes in his arm. The electrodes stimulated the muscles to produce contractions, helping the participant intuitively complete the movements he was thinking of. The system also involved an arm support to stop gravity simply pulling his arm down.

During his training, the participant described how he controlled the neuro-prosthesis: “It’s probably a good thing that I’m making it move without having to really concentrate hard at it. I just think ‘out’ and it just goes.”

After 12 months of having the neuro-prosthesis fitted, the participant was asked to complete day-to-day tasks, including drinking a cup of coffee and feeding himself. First of all, he observed while his arm completed the action under computer control. During this, he thought about making the same movement so that the system could recognise the corresponding brain signals. The two systems were then linked and he was able to use it to drink a coffee and feed himself.

He successfully drank in 11 out of 12 attempts, and it took him roughly 20-40 seconds to complete the task. When feeding himself, he did so multiple times – scooping forkfuls of food and navigating his hand to his mouth to take several bites.

“Although similar systems have been used before, none of them have been as easy to adopt for day-to-day use and they have not been able to restore both reaching and grasping actions,” said Dr Ajiboye. “Our system builds on muscle stimulating electrode technology that is already available and will continue to improve with the development of new fully implanted and wireless brain-computer interface systems. This could lead to enhanced performance of the neuro-prosthesis with better speed, precision and control.” [1]

At the time of the study, the participant had had the neuro-prosthesis implanted for almost two years (717 days) and in this time experienced four minor, non-serious adverse events which were treated and resolved.

Despite its achievements, the neuro-prosthesis still had some limitations, including that movements made using it were slower and less accurate than those made using the virtual reality arm the participant used for training. When using the technology, the participant also needed to watch his arm as he lost his sense of proprioception – the ability to intuitively sense the position and movement of limbs – as a result of the paralysis.

Writing in a linked Comment, Dr Steve Perlmutter, University of Washington, USA, said: “The goal is futuristic: a paralysed individual thinks about moving her arm as if her brain and muscles were not disconnected, and implanted technology seamlessly executes the desired movement… This study is groundbreaking as the first report of a person executing functional, multi-joint movements of a paralysed limb with a motor neuro-prosthesis. However, this treatment is not nearly ready for use outside the lab. The movements were rough and slow and required continuous visual feedback, as is the case for most available brain-machine interfaces, and had restricted range due to the use of a motorised device to assist shoulder movements… Thus, the study is a proof-of-principle demonstration of what is possible, rather than a fundamental advance in neuro-prosthetic concepts or technology. But it is an exciting demonstration nonetheless, and the future of motor neuro-prosthetics to overcome paralysis is brighter.”

…

[1] Quote direct from author and cannot be found in the text of the Article.

Here’s a link to and a citation for the paper,

Restoration of reaching and grasping movements through brain-controlled muscle stimulation in a person with tetraplegia: a proof-of-concept demonstration by A Bolu Ajiboye, Francis R Willett, Daniel R Young, William D Memberg, Brian A Murphy, Jonathan P Miller, Benjamin L Walter, Jennifer A Sweet, Harry A Hoyen, Michael W Keith, Prof P Hunter Peckham, John D Simeral, Prof John P Donoghue, Prof Leigh R Hochberg, Prof Robert F Kirsch. The Lancet DOI: http://dx.doi.org/10.1016/S0140-6736(17)30601-3 Published: 28 March 2017 [online?]

This paper is behind a paywall.

For anyone  who’s interested, you can find the BrainGate website here.

*I initially misidentified the nature of the achievement and stated that Kochevar used a “robotic arm, which is attached to his body” when it was his own reanimated arm. Corrected on April 25, 2017.

Nanotechnology and the US mega science project: BAM (Brain Activity Map) and more

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The Brain Activity Map (BAM) project received budgetary approval as of this morning, Apr. 2, 2013 (I first mentioned BAM in my Mar. 4, 2013 posting when approval seemed imminent). From the news item, Obama Announces Huge Brain-Mapping Project, written by Stephanie Pappas for Yahoo News (Note: Links have been removed),

 President Barack Obama announced a new research initiative this morning (April 2) to map the human brain, a project that will launch with $100 million in funding in 2014.

The Brain Activity Map (BAM) project, as it is called, has been in the planning stages for some time. In the June 2012 issue of the journal Neuron, six scientists outlined broad proposals for developing non-invasive sensors and methods to experiment on single cells in neural networks. This February, President Obama made a vague reference to the project in his State of the Union address, mentioning that it could “unlock the answers to Alzheimer’s.”

In March, the project’s visionaries outlined their final goals in the journal Science. They call for an extended effort, lasting several years, to develop tools for monitoring up to a million neurons at a time. The end goal is to understand how brain networks function.

“It could enable neuroscience to really get to the nitty-gritty of brain circuits, which is the piece that’s been missing from the puzzle,” Rafael Yuste, the co-director of the Kavli Institute for Brain Circuits at Columbia University, who is part of the group spearheading the project, told LiveScience in March. “The reason it’s been missing is because we haven’t had the techniques, the tools.” [Inside the Brain: A Journey Through Time]

Not all neuroscientists support the project, however, with some arguing that it lacks clear goals and may cannibalize funds for other brain research.

….

I believe the $100M mentioned for 2014 would one installment in a series totaling up to $1B or more. In any event, it seems like a timely moment to comment on the communications campaign that has been waged on behalf of the BAM. It reminds me a little of the campaign for graphene, which was waged in the build up to the decision as to which two projects (in a field of six semi-finalists, then narrowed to a field of four finalists) should receive a FET (European Union’s Future and Emerging Technology) 1 billion euro research prize each. It seemed to me even a year or so before the decision that graphene’s win was a foregone conclusion but the organizers left nothing to chance and were relentless in their pursuit of attention and media coverage in the buildup to the final decision.

The most recent salvo in the BAM campaign was an attempt to link it with nanotechnology. A shrewd move given that the US has spent well over $1B since the US National Nanotechnology Initiative (NNI) was first approved in 2000. Linking the two projects means the NNI can lend a little authority to the new project (subtext: we’ve supported a mega-project before and that was successful) while the new project BAM can imbue the ageing NNI with some excitement.

Here’s more about nanotechnology and BAM from a Mar. 27, 2013 Spotlight article by Michael Berger on Nanowerk,

A comprehensive understanding of the brain remains an elusive, distant frontier. To arrive at a general theory of brain function would be an historic event, comparable to inferring quantum theory from huge sets of complex spectra and inferring evolutionary theory from vast biological field work. You might have heard about the proposed Brain Activity Map – a project that, like the Human Genome Project, will tap the hive mind of experts to make headway in the understanding of the field. Engineers and nanotechnologists will be needed to help build ever smaller devices for measuring the activity of individual neurons and, later, to control how those neurons function. Computer scientists will be called upon to develop methods for storing and analyzing the vast quantities of imaging and physiological data, and for creating virtual models for studying brain function. Neuroscientists will provide critical biological expertise to guide the research and interpret the results.

Berger goes on to highlight some of the ways nanotechnology-enabled devices could contribute to the effort. He draws heavily on a study published Mar. 20, 2013 online in ACS (American Chemical Society)Nano. Shockingly, the article is open access. Given that this is the first time I’ve come across an open access article in any of the American Chemical Society’s journals, I suspect that there was payment of some kind involved to make this information freely available. (The practice of allowing researchers to pay more in order to guarantee open access to their research in journals that also have articles behind paywalls seems to be in the process of becoming more common.)

Here’s a citation and a link to the article about nanotechnology and BAM,

Nanotools for Neuroscience and Brain Activity Mapping by A. Paul Alivisatos, Anne M. Andrews, Edward S. Boyden, Miyoung Chun, George M. Church, Karl Deisseroth, John P. Donoghue, Scott E. Fraser, Jennifer Lippincott-Schwartz, Loren L. Looger, Sotiris Masmanidis, Paul L. McEuen, Arto V. Nurmikko, Hongkun Park, Darcy S. Peterka, Clay Reid, Michael L. Roukes, Axel Scherer, Mark Schnitzer, Terrence J. Sejnowski, Kenneth L. Shepard, Doris Tsao, Gina Turrigiano, Paul S. Weiss, Chris Xu, Rafael Yuste, and Xiaowei Zhuang. ACS Nano, 2013, 7 (3), pp 1850–1866 DOI: 10.1021/nn4012847 Publication Date (Web): March 20, 2013
Copyright © 2013 American Chemical Society

As these things go, it’s a readable article for people without a neuroscience education provided they don’t mind feeling a little confused from time to time. From Nanotools for Neuroscience and Brain Activity Mapping (Note: Footnotes and links removed),

The Brain Activity Mapping (BAM) Project (…) has three goals in terms of building tools for neuroscience capable of (…) measuring the activity of large sets of neurons in complex brain circuits, (…) computationally analyzing and modeling these brain circuits, and (…) testing these models by manipulating the activities of chosen sets of neurons in these brain circuits.

As described below, many different approaches can, and likely will, be taken to achieve these goals as neural circuits of increasing size and complexity are studied and probed.

The BAM project will focus both on dynamic voltage activity and on chemical neurotransmission. With an estimated 85 billion neurons, 100 trillion synapses, and 100 chemical neurotransmitters in the human brain,(…) this is a daunting task. Thus, the BAM project will start with model organisms, neural circuits (vide infra), and small subsets of specific neural circuits in humans.

Among the approaches that show promise for the required dynamic, parallel measurements are optical and electro-optical methods that can be used to sense neural cell activity such as Ca2+,(7) voltage,(…) and (already some) neurotransmitters;(…) electrophysiological approaches that sense voltages and some electrochemically active neurotransmitters;(…) next-generation photonics-based probes with multifunctional capabilities;(18) synthetic biology approaches for recording histories of function;(…) and nanoelectronic measurements of voltage and local brain chemistry.(…) We anticipate that tools developed will also be applied to glia and more broadly to nanoscale and microscale monitoring of metabolic processes.

Entirely new tools will ultimately be required both to study neurons and neural circuits with minimal perturbation and to study the human brain. These tools might include “smart”, active nanoscale devices embedded within the brain that report on neural circuit activity wirelessly and/or entirely new modalities of remote sensing of neural circuit dynamics from outside the body. Remarkable advances in nanoscience and nanotechnology thus have key roles to play in transduction, reporting, power, and communications.

One of the ultimate goals of the BAM project is that the knowledge acquired and tools developed will prove useful in the intervention and treatment of a wide variety of diseases of the brain, including depression, epilepsy, Parkinson’s, schizophrenia, and others. We note that tens of thousands of patients have already been treated with invasive (i.e., through the skull) treatments. [emphases mine] While we hope to reduce the need for such measures, greatly improved and more robust interfaces to the brain would impact effectiveness and longevity where such treatments remain necessary.

Perhaps not so coincidentally, there was this Mar. 29, 2013 news item on Nanowerk,

Some human cells forget to empty their trash bins, and when the garbage piles up, it can lead to Parkinson’s disease and other genetic and age-related disorders. Scientists don’t yet understand why this happens, and Rice University engineering researcher Laura Segatori is hoping to change that, thanks to a prestigious five-year CAREER Award from the National Science Foundation (NSF).

…

Segatori, Rice’s T.N. Law Assistant Professor of Chemical and Biomolecular Engineering and assistant professor of bioengineering and of biochemistry and cell biology, will use her CAREER grant to create a toolkit for probing the workings of the cellular processes that lead to accumulation of waste material and development of diseases, such as Parkinson’s and lysosomal storage disorders. Each tool in the kit will be a nanoparticle — a speck of matter about the size of a virus — with a specific shape, size and charge.  [emphases mine] By tailoring each of these properties, Segatori’s team will create a series of specialized probes that can undercover the workings of a cellular process called autophagy.

…

“Eventually, once we understand how to design a nanoparticle to activate autophagy, we will use it as a tool to learn more about the autophagic process itself because there are still many question marks in biology regarding how this pathway works,” Segatori said. “It’s not completely clear how it is regulated. It seems that excessive autophagy may activate cell death, but it’s not yet clear. In short, we are looking for more than therapeutic applications. We are also hoping to use these nanoparticles as tools to study the basic science of autophagy.”

There is no direct reference to BAM but there are some intriguing correspondences.

Finally, there is no mention of nanotechnology in this radio broadcast/podcast and transcript but it does provide more information about BAM (for many folks this was first time they’d heard about the project) and the hopes and concerns this project raises while linking it to the Human Genome Project. From the Mar. 31, 2013 posting of a transcript and radio (Kera News; a National Public Radio station) podcast titled, Somewhere Over the Rainbow: The Journey to Map the Human Brain,

During the State of the Union, President Obama said the nation is about to embark on an ambitious project: to examine the human brain and create a road map to the trillions of connections that make it work.

“Every dollar we invested to map the human genome returned $140 to our economy — every dollar,” the president said. “Today, our scientists are mapping the human brain to unlock the answers to Alzheimer’s.”

Details of the project have slowly been leaking out: $3 billion, 10 years of research and hundreds of scientists. The National Institutes of Health is calling it the Brain Activity Map.

Obama isn’t the first to tout the benefits of a huge government science project. But can these projects really deliver? And what is mapping the human brain really going to get us?

Whether one wants to call it a public relations campaign or a marketing campaign is irrelevant. Science does not take place in an environment where data and projects are considered dispassionately. Enormous amounts of money are spent to sway public opinion and policymakers’ decisions.

ETA Ap. 3, 2013: Here are more stories about BAM and the announcement:

BRAIN Initiative Launched to Unlock Mysteries of Human Mind

Obama’s BRAIN Only 1/13 The Size Of Europe’s

BRAIN Initiative Builds on Efforts of Leading Neuroscientists and Nanotechnologists

Brain-controlled robotic arm means drinking coffee by yourself for the first time in 15 years

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The video shows a woman getting herself a cup of coffee for the first time in 15 years. She’s tetraplegic (aka quadraplegic) and is participating in a research project funded by DARPA (US Defense Advanced Research Projects Agency) for developing neuroprostheses.

Kudos to the researchers and to the woman for her courage and persistence. The May 17, 2012 news item on Nanowerk provides some background,

DARPA launched the Revolutionizing Prosthetics program in 2006 to advance the state of upper-limb prosthetic technology with the goals of improving quality of life for service-disabled veterans and ultimately giving them the option of returning to duty. [emphasis mine] Since then, Revolutionizing Prosthetics teams have developed two anthropomorphic advanced modular prototype prosthetic arm systems, including sockets, which offer increased range of motion, dexterity and control options. Through DARPA-funded work and partnerships with external researchers, the arm systems and supporting technology continue to advance.

The newest development on this project (Revolutionizing Prosthetics) comes from the BrainGate team (mentioned in my April 19, 2012 posting [scroll down about 1/5th of the way) many of whom are affiliated with Brown University.  Alison Abbott’s May 16, 2012 Nature article provides some insight into the latest research,

The study participants — known as Cathy and Bob — had had strokes that damaged their brain stems and left them with tetraplegia and unable to speak. Neurosurgeons implanted tiny recording devices containing almost 100 hair-thin electrodes in the motor cortex of their brains, to record the neuronal signals associated with intention to move.

…

The work is part of the BrainGate2 clinical trial, led by John Donoghue, director of the Brown Institute for Brain Science in Providence. His team has previously reported a trial in which two participants were able to move a cursor on a computer screen with their thoughts.

The neuroscientists are working closely with computer scientists and robotics experts. The BrainGate2 trial uses two types of robotic arm: the DEKA Arm System, which is being developed for prosthetic limbs in collaboration with US military, and a heavier robot arm being developed by the German Aerospace Centre (DLR) as an external assistive device.

In the latest study, the two participants were given 30 seconds to reach and grasp foam balls. Using the DEKA arm, Bob — who had his stroke in 2006 and was given the neural implant five months before the study —- was able to grasp the targets 62% of the time. Cathy had a 46% success rate with the DEKA arm and a 21% success rate with the DLR arm. She successfully raised the bottled coffee to her lips in four out of six trials.

Nature has published the research paper (citation):

Reach and grasp by people with tetraplegia using a neurally controlled robotic arm

Authors: Leigh R. Hochberg, Daniel Bacher, Beata Jarosiewicz, Nicolas Y. Masse, John D. Simeral, Joern Vogel, Sami Haddadin, Jie Liu, Sydney S. Cash, Patrick van der Smagt and John P. Donoghue

Nature, 485, 372–375 (17 May 2012) doi:10.1038/nature11076

The paper is behind a paywall but if you have access, it’s here.

In the excess emotion after watching that video, I forgot for a moment that the ultimate is to repair soldiers and hopefully get them back into the field.