At Washington University, groundbreaking work is underway to turn the concept of machines controlled by human thoughts from science fiction into reality. A few years ago, neurological surgeon and biomedical engineer Eric Leuthardt, MD, and colleagues implanted a grid of electrodes on the brain of an epilepsy patient; they showed that the grid not only served its intended diagnostic purposes but also allowed the patient to control the video game Space Invaders, moving his ship left and right and firing without ever touching the keyboard.
Today, Leuthardt and his colleagues are working to develop more extensive brain-computer interfaces (BCI) that will provide patients with robotic assistance to move their own limbs or to manipulate entirely artificial robotic prosthetics. Leuthardt, who founded and directs the Center for Innovation in Neuroscience and Technology at Washington University, sees a wide range of potential applications for this type of technology, ranging from stroke to neuromuscular disorder and from amputees to patients with paralysis.
Older approaches to BCIs used single implanted electrodes to monitor individual neurons as they fired, but those electrodes frequently become encased by scar tissue, impairing their ability to receive signals. Leuthardt’s team has turned instead to electrocorticography as a platform for translating brain activity into signals that can control BCIs. Research has shown that electrocorticography, which relies on a grid of electrodes enclosed in a polymer sheath and implanted on the surface of the brain, has a lower signal-to-noise ratio, requires less patient training, is less risky and is easier to implement than previous techniques.
To develop technology that can help stroke and cerebral palsy patients walk more naturally and manipulate objects with their hands with greater dexterity, Leuthardt and his colleagues are using brain electrodes implanted for diagnostic purposes to study signals sent from the brain to manipulate the body. Most of these signals cross over, coming from one side of the brain to limbs on the opposite side. But some signals go from one half of the brain to limbs on the same side of the body.
A high percentage of stroke and cerebral palsy patients have damage to just one side of the brain, leading to stiffness and involuntary movements on the opposite side of the body. If researchers can better understand the brain’s ability to control limbs on the same side of the body, they may be able to connect the undamaged side of the brain to BCIs that make it easier for patients to use limbs affected by cerebral palsy.
As science improves its understanding of the basic physiology of the motor cortex and computer scientists continue to miniaturize and improve the processing speeds of computer technology available to biomedical engineers, Leuthardt and his colleagues, writing in a review of the prospects for neuroprosthetics, suggested that neurosurgery may soon be entering a new era.
“In the future, a neurosurgeon’s capabilities will go beyond the ability to remove offending agents such as aneurysms, tumors, and hematomas to prevent the decrement of function,” they wrote. “Rather, he or she will also have the skills and technologies in their clinical armamentarium to engage the nervous system to restore abilities already lost.”