This woman, struggling with tetraplegia, has obtained a level of movement and control with the hand comparable to people without any impairment.
The research came from a team of experts at the University of Pittsburgh and was published Online First in The Lancet.
Until now, a patient with this type of prosthesis has never experienced control and movement to this extent. Therefore, this report symbolizes a major breakthrough in the development of robotic prosthetic limbs controlled by the mind.
The team implanted two microelectrode arrays (a microelectronic tool that attaches brain cells to electronic circuitry) into the left motor cortex of the patient in February of this year. The participant was a woman aged 52 years who received a diagnosis of spinocerebellar degeneration thirteen years prior to the study.
Spinocerebellar degeneration is a rare, inherited disease in which structures in parts of the brain and spinal cord that are responsible for coordination and muscle movement degenerate, and in time, lose function.
However, the patient observed in this study is now considered tetralpegic – paralyzed from the neck and below – due to the progression of her disease. She cannot, therefore, move her arms or her legs voluntarily by herself.
The scientists connected the electrode arrays in the woman’s motor cortex to a robotic hand, and according to the researchers, the movement of the joint and wrist was similar to a human hand.
In order to help the patient learn to use the device, she participated in training for 14 weeks. On the second day of her schooling, just 14 days after implantation, the patient was able to move the prothetic hand on her own, without the help of a computer.
Professor Andrew Schwartz, lead author of the study, explained:
“In developing mind-controlled prosthetics, one of the biggest challenges has always been how to translate brain signals that indicate limb movement into computer signals that can reliably and accurately control a robotic prosthesis.
Most mind-controlled prosthetics have achieved this by an algorithm which involves working through a complex ‘library’ of computer-brain connections. However, we’ve taken a completely different approach here, by using a model-based computer algorithm which closely mimics the way that an unimpaired brain controls limb movement. The result is a prosthetic hand which can be moved far more accurately and naturalistically than previous efforts.”
The woman was involved in extensive training and a testing program which lasted for more than 3 months. The experts hoped that by the end of her program, she would be able to finish assignments showing that she could control the prosthesis over seven degrees of freedom (three-dimensional translation, three-dimensional orientation, one-dimensional grasping).
With the help of her training, the patient was able to finish all of the assignments with a success rate of 91.6%, and she completed the tasks 30 seconds faster than she did at the beginning of the trial.
In order to confirm that the woman’s improvement was clinically significant, for the first time, the team used standard tests, known as Action Research Arm Tests (ARAT), which are normally used to evaluate limb function after people suffer from stroke or other paralyzing incidents.
The researchers added that the next steps to better this prosthetic would be to include sensory elements (for example, help the person distinguish between hot and cold or smooth and rough), and to include wireless technology (eliminating the necessity of wires that connect the patient’s head and their prosthesis).
Professor Grégoire Courtine of the Swiss Federal Institute of Technology Lausanne (EPFL) wrote:
“This bioinspired brain-machine interface is a remarkable technological and biomedical achievement. Though plenty of challenges lie ahead, these sorts of systems are rapidly approaching the point of clinical fruition. Through concerted efforts, and by ensuring that various different strategies available are optimally combined, these kinds of prosthetics might soon become revolutionary treatment models for sensorimotor paralysis.”
A similar report published last year described how an adult male patient, who was paralyzed due to a damaged spinal cord in a motorbike accident, was able to use a brain computer interface to move a prosthetic arm, using only his thoughts.
Written by Sarah Glynn