Reaching, picking up, holding and throwing a ball …… two monkeys with paralyzed hands surprisingly completed such a set of complex movements close to the routine, an achievement that brings hope for the restoration of motor function in human spinal cord injury patients. This is the latest research from Northwestern University Feinberg School of Medicine, where a team of researchers led by Dr. Lee E. Miller, professor of physiology, successfully restored more complex hand movements to paralyzed monkeys with the help of an artificial connection between the brain and muscles. The paper was published in the April 18, 2012 issue of the journal Nature. According to incomplete statistics, more than 130,000 people worldwide survive spinal cord injuries each year, but they will always suffer from severe paralysis. Half of these paralyzed people suffer damage above the sixth cervical vertebra, directly affecting the movement of their limbs. For most of them, regaining the ability to grasp objects is the most realistic boon. It is for this reason that Dr. Miller’s research group has worked to regain the ability to move the hands of paralyzed patients by combining two technologies to generate a neuroprosthetic device with which to replace lost or impaired neurological function. Neither technique is new to medical professionals in the field of brain injury and spinal cord injury rehabilitation. But until then, the two were more like two trains on parallel tracks, running backwards and forwards on their respective paths for the same goal. At a fortuitous bend in the road, the two techniques merged into the same track, producing an unexpected result – intentional fetch. Functional Electrical Stimulation The first technique is Functional Electrical Stimulation (FES). A paralyzed patient starts with a gait speed slower than 0.2m/s and can only walk with one leg, which is often referred to as foot drop. Using one channel of functional electrical stimulation, the dorsal spinal flexors are stimulated to correct the foot drop and the ankle joint is stimulated to lift the foot. After a while, he could increase his gait speed to 0.7m/s and soon did not need crutches. This is not a magical story that happened in a fairy tale, but the FES technique, which has been proven effective since the 1960’s. FES aims to restore some motor ability to patients with spinal cord injuries by using electrical stimulation to activate paralyzed or mildly paralyzed muscles with a precise stimulation sequence and stimulation intensity. FES was first used in the field of rehabilitation medicine in 1961 when Liberson et al. successfully treated seven patients with hemiplegia who had foot drop by stimulating the common peroneal nerve. Over the next 40 years, the FES technique has gradually gained momentum in restoring walking ability in paraplegic patients and has now proven to be a more effective clinical tool for restoring lower extremity ability in paraplegics. There are currently more than 24 research centers around the world that are actively evaluating the role of FES in restoring standing and walking abilities, as well as developing FES mobility assistance systems. To date, however, the only FDA-approved FES system for short-distance walking is the Parastep walking system, which was developed by the University of Illinois in conjunction with a medical center in Chicago and consists of a multichannel stimulator, 12 surface electrodes, and assistive devices to train standing and walking in paraplegic patients with a disability between T4 and T12. Although the FES has been used clinically for a long time and has achieved significant results, the problem of controlling the stimulation signal has limited the further development of the FES. If a suitable stimulation signal is not found, FES cannot achieve a good therapeutic effect, and its motor control of the residual limb can only be performed according to a preset pattern, not in real time according to the patient’s will. A more important reality is that while real progress has been made in restoring motor function to the lower extremities of spinal cord injury patients, FES does not seem to find a suitable solution for restoring function to the upper extremities of paralyzed people until the advent of brain-computer interface technology. Brain-Computer Interface Technology On April 29, 2012, the HKSAR government news website released news that the Chinese University of Hong Kong had recently successfully developed a Chinese brain-computer interface system that converts brain waves into traditional Chinese characters. According to the report, patients who are totally paralyzed and unable to speak can simply wear a wireless brainwave receiver with 16 contact surfaces, face the Chinese stroke input interface on the computer screen, think of the stroke they want to write, and the receiver will receive the instruction to write out the Chinese language. The research team said the system is undoubtedly tens of times slower than direct speech, sign language or handwritten expression, but for patients with severe paralysis, the system breaks through barriers so that they can express themselves, even if only simple phrases, is already a rare and valuable breakthrough. Brain-computer Interface (BCI) is the second technology used in the research of Miller, a physiology professor at Northwestern University. This hybrid technology, formed in the 1970s, involves neurology, psycho-cognitive science, rehabilitation engineering, biomedical engineering and computer science, and has been rapidly developed in the past decade or so, making it possible for humans to use brain signals to communicate with computers or other devices. The essence of BCI technology is to extract and translate the activity of nerve cells. On the one hand, it enables the brain to send commands to control a computer or smart prosthesis, and on the other hand, it allows us to directly interpret some of the information about neural activity and feed it back to the user in the form of images and sounds. Researchers have found that there are three necessary conditions for BCI: first, there must be a signal that reliably reflects the brain’s thinking; second, this signal can be collected in real time and quickly; and third, there is a clear classification of this signal. An important application of BCI technology is for the restoration of motor control in physically disabled and paralyzed patients, allowing human-computer interaction through the mind. For those who are paralyzed with nerve block but still have a limb or muscle damage, the use of BCI to directly control their muscles or perform neurorehabilitation therapy allows them to reestablish their motor abilities and thus achieve the basic movements of their limbs for daily life. Neuroprosthetic device The BCI provides an excellent interface for FES, and Miller, a professor of physiology at Northwestern University, has tried to combine the two technologies to create a powerful neuroprosthetic device. The device consists of two parts: the first is a multi-electrode chip that can be implanted directly into the brain as a BCI, using which researchers can detect the activity of the brain’s 100 brain cells and decode signals that generate muscle and hand movements; the second is an EFS device that transmits electrical currents to paralyzed muscles, causing them to contract. The researchers gave both monkeys local anesthesia that blocked nerve activity at the elbow, causing temporary hand paralysis. With the help of a neuroprosthetic device, a brain chip triggered the FES device directly, bypassing the spinal cord, to achieve intentional, brain-controlled muscle contractions that restored movement to the paralyzed hand, and the paralyzed monkeys could pick up and move small balls in a near-regular manner. In fact, a similar neuroprosthetic device based on a combination of BCI and FES technology has been available since as early as 2008. A team of researchers led by Eberhard Fetz, PhD, at the University of Washington, USA, connected neuronal activity to an FES device. The monkeys learned to activate individual neurons to modulate the FES device, moving the joystick so that neurons previously unrelated to the wrist adapted to accomplish the task. In the same year, experimenters at the University of Pittsburgh implanted an array of microelectrodes into the motor area of the monkey’s brain to capture the electrical discharge signals from multiple nerve cells, which were processed in real time by a computer and converted into control commands for the motorized prosthesis. After a period of training, the monkeys learned to use their own brain nerve signals to directly control the movement of the prosthetic limb and grasp food to feed into their mouths. This research, which was exciting for the field of paralysis rehabilitation at the time, was published in the journal Nature that year. Hong Bo, an expert from the Department of Biomedical Engineering and the Institute of Neuroengineering at Tsinghua University, wrote an article analyzing this research, saying that the University of Pittsburgh study was a consolidation of research findings in this field over the past decade or so. Although there is no significant innovation from the basic principle, but it is the first time the brain directly control the prosthesis with the rest of the body to complete a biological sense of functional action – grasping food, which is another big step forward than previous research. And the latest research by Miller, a professor of physiology at Northwestern University, goes beyond previous findings. Professor Miller wrote in his paper, “Using these neural engineering methods, we can understand some of the important physiological underpinnings of the brain and use it to connect the brain directly to the muscles. This brain-to-muscle connection may one day be used to help people with paralysis due to spinal cord injury to complete daily activities and gain greater independence.” Miller’s findings have furthered the testing and development of advanced neuroprosthetic devices. Researchers in the field are working toward devices that go beyond simple arm movements to achieve fine hand and finger movements, and Miller’s research breaks through the complex hand and finger movements required for neuroprosthetic devices to grasp objects, said Daofen Chen, PhD, program director of the National Institute of Neurological Disorders and Stroke at the National Institutes of Health. However, Professor Miller is also cautious to note that the temporary nerve blocks used in the current study cannot replicate the chronic changes that occur after long-term paralytic brain and spinal cord injury, making it particularly important to test this system in a primate model of long-term paralysis. Regardless, Miller has pushed open a window for paralyzed patients with spinal cord injury, and as long as nerve cells in the brain can still fire, intentional fetching and restoration of motor ability is no longer just a dream.