Paralyzed Individuals Use Thought-Controlled Robotic Arm to Reach and Grasp
In an ongoing clinical trial, a paralyzed woman was able to reach for and sip from a drink on her own – for the first time in nearly 15 years – by using her thoughts to direct a robotic arm. The trial, funded in part by the National Institutes of Health, is evaluating the safety and feasibility of an investigational device called the BrainGate neural interface system. This is a type of brain-computer interface (BCI) intended to put robotics and other assistive technology under the brain’s control. NIH has supported basic and applied research in this area for more than 30 years. In 2009 and 2010, an additional $3.8 million in NIH funding was made possible through the Recovery Act.
The report published in Nature (2012;485:372-375), describes how two individuals – both paralyzed by stroke – learned to use the BrainGate system to make reach-and-grasp movements with a robotic arm, as part of the BrainGate2 clinical trial. The report highlights the potential for long-term use and durability of the BrainGate system, part of which is implanted in the brain to capture the signals underlying intentional movement. It also describes the most complex functions to date that anyone has been able to perform using a BCI.
For the woman, it was the first time since her stroke that she was able to sip a drink without help from a caregiver.
The BrainGate neural interface system consists of a sensor to monitor brain signals and computer software and hardware that turns these signals into digital commands for external devices. The sensor is a baby aspirin-sized square of silicon containing 100 hair-thin electrodes, which can record the activity of small groups of brain cells. It is implanted into the motor cortex, a part of the brain that directs movement.
The latest analysis from the BrainGate2 trial focused on two participants – a 58-year-old woman and a 66-year-old man. Both individuals are unable to speak or move their limbs because of brainstem strokes they had years ago – the woman’s in 1996 and the man’s in 2006. In the trial, both participants learned to perform complex tasks with a robotic arm by imagining the movements of their own arms and hands. In one task, several foam targets were mounted on levers on a tabletop and programmed to pop up one at a time, at different positions and heights. The participants had less than 30 seconds to grasp each target using the DEKA Arm System (Generation 2), which is designed to work as a prosthetic limb for people with arm amputations. One participant was able to grasp the targets 62% of the time, and the other had a 46% success rate. In some sessions, the woman controlled a DLR Light-Weight Robot III arm, which is heavier than the DEKA arm and designed to be used as an external assistive device. She used this arm prior to the DEKA arm in the foam target task, and had a success rate of 21%. In other sessions with the DLR arm, her task was to reach for a bottled drink, bring it to her mouth and sip from a straw. She was able to complete four out of six attempts.
The authors noted the woman’s ability to use the BrainGate was especially encouraging because her stroke occurred nearly 15 years ago and her sensor was implanted more than five years ago. Some researchers have wondered whether neurons in the motor cortex might die or stop generating meaningful signals after years of disuse. Researchers in the field have also worried that years after implantation, the sensor might break down and become less effective at enabling complex motor functions.
As the trial continues, the BrainGate research team needs to test the technology in more individuals. They envision a system that would be stable for decades, wireless and fully automated. For now, the sensor – and therefore the user – must be connected via cables to the rest of the system. Prior to each session with the robotic arms, a technician had to perform a calibration procedure that lasted 31 minutes on average. Improvements are also needed to enhance the precision and speed of control. In the foam target task, for example, a successful reach-and-grasp motion typically took almost 10 seconds.
The ultimate goal for helping people with paralysis is to reconnect the brain directly to paralyzed limbs rather than robotic ones. In the future, the BrainGate system might be used to control a functional electrical stimulation (FES) device, which delivers electrical stimulation to paralyzed muscles. Such technology has shown promise in monkeys. The Eunice Kennedy Shriver National Institute for Child Health and Human Development (NICHD) has long supported the clinical trial research for BrainGate, with the goal of enabling mental control of an FES system for limb movement. In previous reports from the BrainGate2 trial, a participant was able to use the BrainGate system to direct the movements of a virtual, computer-animated arm designed to simulate FES control of a real arm.
To support this research, NIH has worked closely with the Department of Veterans Affairs (VA) and the Defense Advanced Research Projects Agency (DARPA), the research arm of the Department of Defense. DARPA supports development of the DEKA arm. Development of the DLR arm is funded by the German aerospace agency DLR. NIH has supported the fundamental neuroscience and BCI development, and the clinical research in collaboration with the VA.
The BrainGate trial began in 2004 and was run by Cyberkinetics Inc., in collaboration with Brown University and MGH. NICHD began funding the trial in 2005. After Cyberkinetics withdrew from the research for financial reasons, funding continued through this NICHD contract, MGH became the clinical trial and administrative lead, and the trial was renamed BrainGate2. The trial is currently recruiting.