Every action our body performs begins with a thought, and with every thought comes an electrical signal. The electrical signals can be received by the brain-computer interface, consisting of an electroencephalograph (EEG) or an implanted electrode, which can then be translated, and then sent to the performing hardware to produce the desired action. BCI is an alternative system built on artificial mechanisms and acts as a bridge between the brain and external devices. The aim of BCI is to convey human intentions to external devices by directly extracting brain signals. Eventually, the brain and computers would be highly integrated.
The brain-computer interface (BCI) allows people to use their thoughts to control not only themselves, but the world around them. BCI enables a bidirectional communication between a brain and an external device, bidirectional generally includes direct neural readout and feedback and direct neural write-in.
Over the last few decades, several neuroengineering and neuroscience studies have demonstrated how Brain Computer Interface (BCI) technology can uncover the neural mechanisms underlying various tasks and translate them into commands that control an application or device
Brain-computer interfaces are being applied in neuroprosthetics, through which paralyzed persons are able to control robotic arms, neurogaming where one can control keyboard, mouse etc using their thoughts and play games, neuroanalysis (psychology), and in defense to control robotic soldiers or fly planes with thoughts.
BCIs may replace lost functions, such as speaking or moving. They may restore the ability to control the body, such as by stimulating nerves or muscles that move the hand. BCIs have also been used to improve functions, such as training users to improve the remaining function of damaged pathways required to grasp. BCIs can also enhance function, like warning a sleepy driver to wake up. Finally, a BCI might supplement the body’s natural outputs, such as through a third hand.
While many studies have demonstrated the theoretic potential of BCI, especially by deploying novel machine learning methods for detecting distinct task-specific attributes of the brain, a point of concern that remains is that the studies are still confined to lab settings and mostly limited to healthy able-bodied subjects. A few case-studies using invasive and non-invasive BCIs have demonstrated the application of BCI as a motor assistive technology for survivors of spinal cord injury (SCI).
Brain Computer Interface technology
BCI technology by providing direct communication between the brain and external devices will enable new ways of human interacting with their devices. In recent years, advances in machine learning (ML) have enabled the development of more advanced BCI spellers, devices that allow people to communicate with computers using their thoughts. In the next few years, we might be able to control our PowerPoint presentation or Excel files using only our brains. Some prototypes can translate brain activity into text or instructions for a computer, and in theory, as the technology improves, we’ll see people using BCIs to write memos or reports at work.
But new use cases are being identified all the time. For example, BCIs can now be used as a neurofeedback training tool to improve cognitive performance. For example, your BCI could detect that your attention level is too low compared with the importance of a given meeting or task and trigger an alert. BCIs can detect the mental state of a worker and adjust nearby devices accordingly (smart home utilization). for example, It could adapt the lighting of your office based on how stressed you are, or prevent you from using your company car if drowsiness is detected.
A Toronto-based startup called “Muse” has developed a sensing headband that gives real-time information about what’s going on in your brain. The startup already has a “Corporate Wellness Program” to “help your employees lower stress, increase resilience, and improve their engagement.” Other headbands on the market also use proprietary sensors to detect brain signals and leverage machine learning algorithms to provide insights into the engagement levels of users/workers. They can track whether someone is focused or distracted.
Researchers are also experimenting with “passthoughts” as an alternative to passwords. Soon, we might log into our various devices and platforms using our thoughts. As described in this IEEE Spectrum article, “When we perform mental tasks like picturing a shape or singing a song in our heads, our brains generate unique neuronal electrical signals. A billion people could mentally hum the same song and no two brain-wave patterns generated by that task would be alike. An electroencephalograph (EEG) would read those brain waves using noninvasive electrodes that record the signals. The unique patterns can be used like a password or biometric identification.”
Different techniques are used to measure brain activity for BCIs. Different BCI tools allow users to access and to use these signals with various levels of accuracy and invasiveness. Most BCIs have used electrical signals that are detected using electrodes placed invasively within or on the surface of the cortex, or noninvasively on the surface of the scalp [electroencephalography (EEG)]. Some BCIs have been based on metabolic activity that is measured noninvasively, such as through functional magnetic resonance imaging (fMRI).
There are three fundamental techniques to interface with the brain; non-inasive such as electro-encephalography (EEG), invasive through direct connections and electro-corticography (ECoG), also known as intracranial EEG – a sort of half-way house involving electrodes placed on the brain’s exposed surface, rather than hardwired into the brain itself. Invasive BCI are technologies that provide high resolution but require neurosurgery. They require regulatory approvals, hence manufacturers are less willing to fund clinical trials associated with the approval process.
Current implantable devices are not well matched with body tissues in terms of their mechanical, chemical, and physical properties. “These elements of mismatch reduce the overall performance of current implantable technology in three ways. First, the difference in mechanical properties (i.e., the elasticity) can cause local tissue damage that compromises the fidelity of measurements. Second, changing between ionic and electronic transduction decreases the information density and stimulation specificity. Finally, the materials that are typically used in microelectronic implants are susceptible to rapid protein adsorption, which initiates a cascade of local inflammation and scarring. The biological response to the presence of foreign material (such as an implant) can also compromise bidirectional communication.”
Non-Invasive BCI have gained popularity in the recent times and are expected to grow at a fast pace in the near future because it provides least discomfort and negligible chance of infection due to electrode use. Progress in non-invasive electroencephalography (EEG)-based brain-computer interface (BCI) research, development and innovation has accelerated in recent years. New brain signal signatures for inferring user intent and more complex control strategies have been the focus of many recent developments. Major advances in recording technology, signal processing techniques and clinical applications, tested with patient cohorts as well as non-clinical applications have been reported, writes Damien Coyle.
Non-invasive BCI has found multiple uses in the areas of medicine such as motor restoration, wheelchair assistance, and treatment of neurological disorders. However noninvasive BCIs suffer from poor efficiency and accuracy, are slow and somewhat uncertain at present, they also tend to make high cognitive demands on the user.
U C Berkeley engineers have built the first dust-sized, wireless sensors that can be implanted in the body without surgery, bringing closer the day when a Fitbit-like device could monitor internal nerves, muscles or organs in real time.Because these batteryless sensors could also be used to stimulate nerves and muscles, the technology also opens the door to “electroceuticals” to treat disorders such as epilepsy or to stimulate the immune system or tamp down inflammation.
Instead of invasive brain surgery, DARPA has developed small brain modem that enters the bloodstream via a catheter and then transmits data. The US military recently successfully implanted and tested its first ‘brain modem’ on an animal subject. Neurologists injected tiny sensors into livestocks’ veins and then recorded the electrical impulses that control the animals’ movements for six months.
The tiny, implanted chip, developed by the Defense Advanced Research Projects Agency (Darpa), uses a tiny sensor that travels through blood vessels, lodges in the brain and records neural activity. The sensor, called a ‘stentrode’, a combination of the words ‘stent’ and ‘electrode’, is the first step in the military’s desire to allow soldiers to control machinery with their minds. The stentrode is the size of a paperclip, flexible and injectable.
“The original goal of the neural dust project was to imagine the next generation of brain-machine interfaces, and to make it a viable clinical technology,” said neuroscience graduate student Ryan Neely. “If a paraplegic wants to control a computer or a robotic arm, you would just implant this electrode in the brain and it would last essentially a lifetime.”
BCI in form of Artificial Skin
John Rogers at the University of Illinois at Urbana-Champaign and his team have built a Brain Computer Interface, in the form of flexible electronic skin that conforms to the body. The interface comprising just of small patch of gold electrodes sticks to the skin through van der Waals forces like a digital tattoo. The patch applied behind the ear, falls off when the build-up of dead skin beneath it loosens its grip.
Their solution does away with the cumbersome electrodes, annoying gels and wires of conventional EEGs described by Rogers as a “rat’s nest of wires attached to devices that interface to the skin with tape and gels and bulky metallic objects”. The team is now working on wireless transmission of data and power, allowing it to work even if the wearer is moving.
Invasive BCI have greater application in neuroprosthetics compared to non-invasive BCI since in order to understand/regulate the neural connectivity of specific brain areas, it becomes necessary to introduce neural implants (electrodes). One of the critical technologies is material used to make electrodes used to make Brain Computer Interfaces.
Lund University’s Breakthrough for electrode implants
“There are several elements that must go hand in hand for us to be able to record neuronal signals from the brain with decisive results. First, the electrode must be bio-friendly, that is, we have to be confident that it does not cause any significant damage to the brain tissue. Second, the electrode must be flexible in relation to the brain tissue. Remember that the brain floats in fluid inside the skull and moves around when we, for instance, breathe or turn our heads.”
The Lund researchers’ Professor Jens Schouenborg and Dr Lina Pettersson have developed tailored electrodes, which they call 3-D electrodes, are unique in that they are extremely soft and flexible in all three dimensions, in a way that enables stable recordings from the neurons over a long time.
In order to implant such electrodes, the researchers have developed a technique for encapsulating the electrodes in a hard but dissolvable gelatine material that is also very gentle on the brain. The electrodes are made of 4 mm gold leads and individually insulated with 4 mm parylene. The array of electrodes consists of eight flexible channels, designed to follow the movement of the brain. Both the electrode and implantation technology, which have been tested on rats, are patented by NRC researchers, in Europe and the US, among other places.
“This technology retains the electrodes in their original form inside the brain and can monitor what happens inside virtually undisturbed and normally functioning brain tissue”, says Johan Agorelius, a doctoral student in the project.
Until now, developed flexible electrodes have not been able to maintain their shape when implanted, which is why they have been fixated on a solid chip that limits their flexibility, among other things. Other types of electrodes that are used are much stiffer. The result in both cases is that they rub against and irritate the brain tissue, and the nerve cells around the electrodes die.
“The signals then become misleading or completely non-existent. Our new technology enables us to implant as flexible electrodes as we want, and retain the exact shape of the electrode within the brain”, says Johan Agorelius.
“This creates entirely new conditions for our understanding of what happens inside the brain and for the development of more effective treatments for diseases such as Parkinson’s disease and chronic pain conditions than can be achieved using today’s techniques”, concludes Jens Schouenborg.
Electronic dura mater for long-term multimodal neural interfaces
Team of researchers at a Swiss technology institute , Pavel Musienko and others have developed a new ultra flexible electrodes modeled on dura matter, the protective membrane of the brain and spinal cord, that can both stimulate and record from neurons.
Most of current electrode implants—even thin, plastic interfaces—present high elastic moduli in the gigapascal range, thus are rigid compared to neural tissues. “The mechanical mismatch between soft neural tissues and stiff neural implants hinders the long-term performance of implantable neuroprostheses. Here, we designed and fabricated soft neural implants with the shape and elasticity of dura mater, the protective membrane of the brain and spinal cord.”
“The implant, which we called electronic dura mater or e-dura, integrates a transparent silicone from substrate (120 mm in thickness), stretchable gold interconnects (35 nm in thickness), soft electrodes coated with a platinum-silicone composite (300 mm in diameter), and a compliant fluidic microchannel (100 mm by 50 mm in cross section).” The interconnects and electrodes transmit electrical excitation and transfer electrophysiological signals. The microfluidic channel, termed chemotrode , delivers drugs locally .
They next tested the long-term biointegration of soft implants compared to stiff, plastic implants (6 weeks of implantation). Both types of implants were inserted into the subdural space of lumbosacral segments in healthy rats. They found that rats with the stiff implant began to have trouble walking within just a few weeks, and later examination showed both inflammation and deformation of their spinal cords. The rats with the e-dura implant displayed no such motor problems or physiological degradation. The electrodes also proved to be effective in accurately recorded from and stimulated neurons in the brain and spinal cord.
University of Melbourne scientists develop BCI which gets implanted in the brain without surgery
Australian scientists funded by the US Defense Advanced Research Projects Agency (Darpa) have developed a tiny, matchstick-sized Brain Computer interface called a stentrode. This stentrode is flexible enough to be able to pass through the blood vessels and get implanted into the motor cortex, the brain’s control centre – bypassing the need for complex invasive brain surgery.
The device would capture and decode the brain signals and then wirelessly transmit appropriate commands through the skin to enable control of an exoskeleton attached to their limbs simply by thinking about it.
The stentrode could also benefit people with Parkinson’s disease, motor neurone disease, obsessive compulsive disorder and depression and could even predict and manage seizures in epileptic patients. The work is the result of close collaboration between the University of Melbourne, the Royal Melbourne Hospital and the Florey Institute of Neuroscience and Mental Health.
In late 2017, a select group of paralysed patients from the Royal Melbourne and Austin Hospitals in Australia will be chosen for the trial, where they will be implanted with the stentrode. If the trial succeeds, the technology could become commercially available in as little as six years.
Researchers demonstrate first human use of high-bandwidth wireless brain-computer interface in March 2021
For years, investigational BCIs used in clinical trials have required cables to connect the sensing array in the brain to computers that decode the signals and use them to drive external devices.
A participant in the BrainGate clinical trial uses wireless transmitters that replace the cables normally used to transmit signals from sensors inside the brain. Now, for the first time, BrainGate clinical trial participants with tetraplegia have demonstrated use of an intracortical wireless BCI with an external wireless transmitter. The system is capable of transmitting brain signals at single-neuron resolution and in full broadband fidelity without physically tethering the user to a decoding system. The traditional cables are replaced by a small transmitter about 2 inches in its largest dimension and weighing a little over 1.5 ounces. The unit sits on top of a user’s head and connects to an electrode array within the brain’s motor cortex using the same port used by wired systems.
For a study published in IEEE Transactions on Biomedical Engineering, two clinical trial participants with paralysis used the BrainGate system with a wireless transmitter to point, click and type on a standard tablet computer. The study showed that the wireless system transmitted signals with virtually the same fidelity as wired systems, and participants achieved similar point-and-click accuracy and typing speeds.
“We’ve demonstrated that this wireless system is functionally equivalent to the wired systems that have been the gold standard in BCI performance for years,” said John Simeral, an assistant professor of engineering (research) at Brown University, a member of the BrainGate research consortium and the study’s lead author. “The signals are recorded and transmitted with appropriately similar fidelity, which means we can use the same decoding algorithms we used with wired equipment. The only difference is that people no longer need to be physically tethered to our equipment, which opens up new possibilities in terms of how the system can be used.”
The researchers say the study represents an early but important step toward a major objective in BCI research: a fully implantable intracortical system that aids in restoring independence for people who have lost the ability to move. While wireless devices with lower bandwidth have been reported previously, this is the first device to transmit the full spectrum of signals recorded by an intracortical sensor. That high-broadband wireless signal enables clinical research and basic human neuroscience that is much more difficult to perform with wired BCIs.
Signal processing and Machine learning
A major proportion of BCI literature has focused on improving performance of BCI applications by enhancing the decoding performance of signal processing and machine learning algorithms. While this is an important contributing factor, research has also demonstrated that mutual learning of the machine and the user is critical for a successful closed-loop implementation of BCI.
In any case, the fundamental deciding factor for the efficiency of a BCI system is how well the end-user can generate distinct and consistent brain activity corresponding to each mental task. This in turn results in well-calibrated BCI decoders that can offer better real-time performance. However, the calibration paradigms for data collection, often involve time-consuming, monotonous and non-engaging visual interfaces.