Posts tagged electrodes
Articles and news from the latest research reports.
Novel wireless brain sensor
A team of neuroengineers based at Brown University has developed a fully implantable and rechargeable wireless brain sensor capable of relaying real-time broadband signals from up to 100 neurons in freely moving subjects. Several copies of the novel low-power device, described in the Journal of Neural Engineering, have been performing well in animal models for more than year, a first in the brain-computer interface field. Brain-computer interfaces could help people with severe paralysis control devices with their thoughts.
Arto Nurmikko, professor of engineering at Brown University who oversaw the device’s invention, is presenting it this week at the 2013 International Workshop on Clinical Brain-Machine Interface Systems in Houston.
“This has features that are somewhat akin to a cell phone, except the conversation that is being sent out is the brain talking wirelessly,” Nurmikko said.
Neuroscientists can use such a device to observe, record, and analyze the signals emitted by scores of neurons in particular parts of the animal model’s brain.
Meanwhile, wired systems using similar implantable sensing electrodes are being investigated in brain-computer interface research to assess the feasibility of people with severe paralysis moving assistive devices like robotic arms or computer cursors by thinking about moving their arms and hands.
This wireless system addresses a major need for the next step in providing a practical brain-computer interface,” said neuroscientist John Donoghue, the Wriston Professor of Neuroscience at Brown University and director of the Brown Institute for Brain Science.
Tightly packed technology
In the device, a pill-sized chip of electrodes implanted on the cortex sends signals through uniquely designed electrical connections into the device’s laser-welded, hermetically sealed titanium “can.” The can measures 2.2 inches (56 mm) long, 1.65 inches (42 mm) wide, and 0.35 inches (9 mm) thick. That small volume houses an entire signal processing system: a lithium ion battery, ultralow-power integrated circuits designed at Brown for signal processing and conversion, wireless radio and infrared transmitters, and a copper coil for recharging — a “brain radio.” All the wireless and charging signals pass through an electromagnetically transparent sapphire window.
In all, the device looks like a miniature sardine can with a porthole.
But what the team has packed inside makes it a major advance among brain-machine interfaces, said lead author David Borton, a former Brown graduate student and postdoctoral research associate who is now at Ecole Polytechnique Federale Lausanne in Switzerland.
“What makes the achievement discussed in this paper unique is how it integrated many individual innovations into a complete system with potential for neuroscientific gain greater than the sum of its parts,” Borton said. “Most importantly, we show the first fully implanted microsystem operated wirelessly for more than 12 months in large animal models — a milestone for potential [human] clinical translation.”
The device transmits data at 24 Mbps via 3.2 and 3.8 Ghz microwave frequencies to an external receiver. After a two-hour charge, delivered wirelessly through the scalp via induction, it can operate for more than six hours.
“The device uses less than 100 milliwatts of power, a key figure of merit,” Nurmikko said.
Co-author Ming Yin, a Brown postdoctoral scholar and electrical engineer, said one of the major challenges that the team overcame in building the device was optimizing its performance given the requirements that the implant device be small, low-power and leak-proof, potentially for decades.
“We tried to make the best tradeoff between the critical specifications of the device, such as power consumption, noise performance, wireless bandwidth and operational range,” Yin said. “Another major challenge we encountered was to integrate and assemble all the electronics of the device into a miniaturized package that provides long-term hermeticity (water-proofing) and biocompatibility as well as transparency to the wireless data, power, and on-off switch signals.”
With early contributions by electrical engineer William Patterson at Brown, Yin helped to design the custom chips for converting neural signals into digital data. The conversion has to be done within the device, because brain signals are not produced in the ones and zeros of computer data.
Ample applications
The team worked closely with neurosurgeons to implant the device in three pigs and three rhesus macaque monkeys. The research in these six animals has been helping scientists better observe complex neural signals for as long as 16 months so far. In the new paper, the team shows some of the rich neural signals they have been able to record in the lab. Ultimately this could translate to significant advances that can also inform human neuroscience.
Current wired systems constrain the actions of research subjects, Nurmikko said. The value of wireless transmission is that it frees subjects to move however they intend, allowing them to produce a wider variety of more realistic behaviors. If neuroscientists want to observe the brain signals produced during some running or foraging behaviors, for instance, they can’t use a cabled sensor to study how neural circuits would form those plans for action and execution or strategize in decision making.
In the experiments in the new paper, the device is connected to one array of 100 cortical electrodes, the microscale individual neural listening posts, but the new device design allows for multiple arrays to be connected, Nurmikko said. That would allow scientists to observe ensembles of neurons in multiple related areas of a brain network.
The new wireless device is not approved for use in humans and is not used in clinical trials of brain-computer interfaces. It was designed, however, with that translational motivation.
“This was conceived very much in concert with the larger BrainGate* team, including neurosurgeons and neurologists giving us advice as to what were appropriate strategies for eventual clinical applications,” said Nurmikko, who is also affiliated with the Brown Institute for Brain Science.
Borton is now spearheading the development of a collaboration between EPFL and Brown to use a version of the device to study the role of the motor cortex in an animal model of Parkinson’s disease.
Meanwhile the Brown team is continuing work on advancing the device for even larger amounts of neural data transmission, reducing its size even further, and improving other aspects of the device’s safety and reliability so that it can someday be considered for clinical application in people with movement disabilities.
(Source: news.brown.edu)
World premiere of muscle and nerve controlled arm prosthesis
For the first time an operation has been conducted, at Sahlgrenska University Hospital, where electrodes have been permanently implanted in nerves and muscles of an amputee to directly control an arm prosthesis. The result allows natural control of an advanced robotic prosthesis, similarly to the motions of a natural limb.
A surgical team led by Dr Rickard Brånemark, Sahlgrenska University Hospital, has carried out the first operation of its kind, where neuromuscular electrodes have been permanently implanted in an amputee. The operation was possible thanks to new advanced technology developed by Max Ortiz Catalan, supervised by Rickard Brånemark at Sahlgrenska University Hospital and Bo Håkansson at Chalmers University of Technology.
“The new technology is a major breakthrough that has many advantages over current technology, which provides very limited functionality to patients with missing limbs,” says Rickard Brånemark.
Big challenges
There have been two major issues on the advancement of robotic prostheses: 1) how to firmly attach an artificial limb to the human body; 2) how to intuitively and efficiently control the prosthesis in order to be truly useful and regain lost functionality.
“This technology solves both these problems by combining a bone anchored prosthesis with implanted electrodes,” said Rickard Brånemark, who along with his team has developed a pioneering implant system called Opra, Osseointegrated Prostheses for the Rehabilitation of Amputees.
A titanium screw, so-called osseointegrated implant, is used to anchor the prosthesis directly to the stump, which provides many advantages over a traditionally used socket prosthesis.
“It allows complete degree of motion for the patient, fewer skin related problems and a more natural feeling that the prosthesis is part of the body. Overall, it brings better quality of life to people who are amputees,” says Rickard Brånemark.
How it works
Presently, robotic prostheses rely on electrodes over the skin to pick up the muscles electrical activity to drive few actions by the prosthesis. The problem with this approach is that normally only two functions are regained out of the tens of different movements an able-body is capable of. By using implanted electrodes, more signals can be retrieved, and therefore control of more movements is possible. Furthermore, it is also possible to provide the patient with natural perception, or “feeling”, through neural stimulation.
“We believe that implanted electrodes, together with a long-term stable human-machine interface provided by the osseointegrated implant, is a breakthrough that will pave the way for a new era in limb replacement,” says Rickard Brånemark.
The patient
The first patient has recently been treated with this technology, and the first tests gave excellent results. The patient, a previous user of a robotic hand, reported major difficulties in operating that device in cold and hot environments and interference from shoulder muscles. These issues have now disappeared, thanks to the new system, and the patient has now reported that almost no effort is required to generate control signals. Moreover, tests have shown that more movements may be performed in a coordinated way, and that several movements can be performed simultaneously.
“The next step will be to test electrical stimulation of nerves to see if the patient can sense environmental stimuli, that is, get an artificial sensation. The ultimate goal is to make a more natural way to replace a lost limb, to improve the quality of life for people with amputations,” says Rickard Brånemark.
First signals from brain nerve cells with ultrathin nanowires
Electrodes operated into the brain are today used in research and to treat diseases such as Parkinson’s. However, their use has been limited by their size. At Lund University in Sweden, researchers have, for the first time, succeeded in implanting an ultrathin nanowire-based electrode and capturing signals from the nerve cells in the brain of a laboratory animal.
The researchers work at Lund University’s Neuronano Research Centre in an interdisciplinary collaboration between experts in subjects including neurophysiology, biomaterials, electrical measurements and nanotechnology. Their electrode is composed of a group of nanowires, each of which measures only 200 nanometres (billionths of a metre) in diameter.
Such thin electrodes have previously only been used in experiments with cell cultures.
“Carrying out experiments on a living animal is much more difficult. We are pleased that we have succeeded in developing a functioning nano-electrode, getting it into place and capturing signals from nerve cells”, says Professor Jens Schouenborg, who is head of the Neuronano Research Centre.
He sees this as a real breakthrough, but also as only a step on the way. The research group has already worked for several years to develop electrodes that are thin and flexible enough not to disturb the brain tissue, and with material that does not irritate the cells nearby. They now have the first evidence that it is possible to obtain useful nerve signals from nanometre-sized electrodes.
The research will now take a number of directions. The researchers want to try and reduce the size of the base to which the nanowires are attached, improve the connection between the electrode and the electronics that receive the signals from the nerve cells, and experiment with the surface structure of the electrodes to see what produces the best signals without damaging the brain cells.
“In the future, we hope to be able to make electrodes with nanostructured surfaces that are adapted to the various parts of the nerve cells – parts that are no bigger than a few billionths of a metre. Then we could tailor-make each electrode based on where it is going to be placed and what signals it is to capture or emit”, says Jens Schouenborg.
When an electrode is inserted into the brain of a patient or a laboratory animal, it is generally anchored to the skull. This means that it doesn’t move smoothly with the brain, which floats inside the skull, but rather rubs against the surrounding tissue, which in the long term causes the signals to deteriorate. The Lund group’s electrodes will instead be anchored by their surface structure.
“With the right pattern on the surface, they will stay in place yet still move with the body – and the brain – thereby opening up for long-term monitoring of neurones”, explains Jens Schouenborg.
He praises the collaboration between medics, physicists and others at the Neuronano Research Centre, and mentions physicist Dmitry B. Suyatin in particular. He is the principal author of the article which the researchers have now published in the international journal PLOS ONE.
The overall goal of the Neuronano Research Centre is to develop electrodes that can be inserted into the brain to study learning, pain and other mechanisms, and, in the long term, to treat conditions such as chronic pain, depression and Parkinson’s disease.
(Source: lunduniversity.lu.se)
Fighting disease deep inside the brain
Some 90,000 patients per year are treated for Parkinson’s disease, a number that is expected to rise by 25 percent annually. Deep Brain Stimulation (DBS), which consists of electrically stimulating the central or peripheral nervous system, is currently standard practice for treating Parkinson’s, but it can involve long, expensive surgeries with dramatic side effects. Miniature, ultra-flexible electrodes developed in Switzerland, however, could be the answer to more successful treatment for this and a host of other health issues.
Today, Professor Philippe Renaud of the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland reports on soft arrays of miniature electrodes developed in his Microsystems Laboratory that open new possibilities for more accurate and local DBS. At the 2013 Annual Meeting of the American Association for the Advancement of Science (AAAS) in Boston, in a symposium called “Engineering the Nervous System: Solutions to Restore Sight, Hearing, and Mobility,” he announces the start of clinical trials and early, yet promising results in patients, and describes new developments in ultra-flexible electronics that can conform to the contours of the brainstem—in the brain itself—for treating other disorders.
At AAAS, Renaud outlines the technology behind these novel electronic interfaces with the nervous system, the associated challenges, and their immense potential to enhance DBS and treat disease, even how ultra flexible electronics could lead to the auditory implants of the future and the restoration of hearing. “Although Deep Brain Stimulation has been used for the past two decades, we see little progress in its clinical outcomes,” Renaud says. “Microelectrodes have the potential to open new therapeutic routes, with more efficiency and fewer side effects through a much better and finer control of electrical activation zones.” The preliminary clinical trials related to this research are being done in conjunction with EPFL spin-off company Aleva Neurotherapeutics, the first company in the world to introduce microelectrodes in Deep Brain Stimulation leading to more precise directional stimulation.
Simple Innovation to Electrodes Makes a Big Difference
The electroencephalogram (EEG) for human uses has been around since 1924. Small metal discs placed along the scalp measure electrical activity in the human brain, important in diagnosing or evaluating epilepsy, sleep disorders and other conditions.
But these electrodes have changed little since their introduction, and are far from perfect. Among other things, they pick up extraneous noise and movement in addition to brain wave activity, often making the readings difficult to interpret.
Walt Besio thinks he has a better way.
The National Science Foundation-funded scientist, who is associate professor of biomedical engineering at the University of Rhode Island, has invented a new and improved electrode, one that produces a performance difference that he says is akin to “taking the rabbit ears you used to have for your television set, and converting to high definition.”
His innovation is relatively simple, but apparently makes a big difference. Besio added two new metal rings around the basic disc, a change that eliminates outside noises and improves spatial resolution.
"EEG has two main problems: It’s very noisy and contaminated with artifacts, and it’s spatial resolution is bad," he explains. "We have improved the signal-to-noise ratio. It’s four times better than it was before. Because it is now a very local signal, it means we can put electrodes closer together, which improves spatial resolution, meaning you can better determine where the signal is coming from."
The additional rings work almost like an inner tube tossed on top of a rippling body of water. “The water is flat in the center of the inner tube and choppy on the outside,” he says. “The outer rings on the electrodes behave like that inner tube.”
For researchers and clinicians, having improved electrodes could open up potential new uses, as well as improve current ones-more accurate epilepsy diagnosis, for example, as well as the promise of “reading” someone’s thoughts in the future, with the goal, for example, of activating an otherwise inert body part, such as an arm or leg, and ultimately helping people with spinal cord injuries.
The aim is to have the highly sensitive electrodes first translate a person’s thoughts into electrical impulses that can be read by a computer, then, eventually move to robots, and later, limbs. Other scientists are conducting similar research, but Besio wants to show “that it works better with these types of electrodes.”
Protein-Based Coating Could Help Rehabilitate Long-Term Brain Function
Tuesday, July 31, 2012
TAU researchers develop bioactive coating to “camouflage” neutral electrodes
Brain-computer interfaces are at the cutting edge for treatment of neurological and psychological disorder, including Parkinson’s, epilepsy, and depression. Among the most promising advance is deep brain stimulation (DBS) — a method in which a silicon chip implanted under the skin ejects high frequency currents that are transferred to the brain through implanted electrodes that transmit and receive the signals. These technologies require a seamless interaction between the brain and the hardware.
But there’s a catch. Identified as foreign bodies by the immune system, the brain attacks the electrodes and forms a barrier to the brain tissue, making it impossible for the electrodes to communicate with brain activity. So while the initial implantation can diminish symptoms, after a few short years or even months, the efficacy of this therapy begins to wane.
Now Aryeh Taub of Tel Aviv University's School of Psychological Sciences, along with Prof. Matti Mintz, Roni Hogri and Ari Magal of TAU’s School of Psychological Sciences and Prof. Yosi Shacham-Diamand of TAU’s School of Electrical Engineering, has developed a bioactive coating which not only “camouflages” the electrodes in the brain tissue, but actively suppresses the brain’s immune response. By using a protein called an “interleukin (IL)-1 receptor antagonist” to coat the electrodes, the multi-disciplinary team of researchers has found a potential resolution to turn a method for short-term relief into a long-term solution. This development was reported in the Journal of Biomedical Materials Research.
Limiting the immune response
To overcome the creation of the barrier between the tissue and the electrode, the researchers sought to develop a method for placing the electrode in the brain tissue while hiding the electrode from the brain’s immune defenses. Previous research groups have coated the electrodes with various proteins, says Taub, but the TAU team decided to take a different approach by using a protein that is active within the brain itself, thereby suppressing the immune reaction against the electrodes.
In the brain, the IL-1 receptor antagonist is crucial for maintaining physical stability by localizing brain damage, Taub explains. For example, if a person is hit on the head, this protein works to create scarring in specific areas instead of allowing global brain scarring. In other words, it stops the immune system from overreacting. The team’s coating, the first to be developed from this particular protein, not only integrates the electrodes into the brain tissue, but allows them to contribute to normal brain functioning.
In pre-clinical studies with animal models, the researchers found that their coated electrodes perform better than both non-coated and “naïve protein”-coated electrodes that had previously been examined. Measuring the number of damaged cells at the site of implantation, researchers found no apparent difference between the site of electrode implantation and healthy brain tissue elsewhere, Taub says. In addition, evidence suggests that the coated electrodes will be able to function for long periods of time, providing a more stable and long-term treatment option.
Restoring brain function
Approximately 30,000 people worldwide are currently using deep brain stimulation (DBS) to treat neurological or psychological conditions. And DBS is only the beginning. Taub believes that, in the future, an interface with the ability to restore behavioral or motor function lost due to tissue damage is achievable — especially with the help of their new electrode coating.
"We duplicate the function of brain tissue onto a silicon chip and transfer it back to the brain," Taub says, explaining that the electrodes will pick up brain waves and transfer these directly to the chip. "The chip then does the computation that would have been done in the damaged tissue, and feeds the information back into the brain — prompting functions that would have otherwise gotten lost."
Source: Tel Aviv University