The Power of a Grasp
Published January 2015
A Breakthrough in BMI Helps Patients Regain Grip
Patients who have paralyzed or amputated hands are one step closer to recovering an essential ability: grasp.Scientists can already use brain signals to control external devices such as prosthetic arms and hands. But many brain machine interfaces (BMIs) – the mechanisms used to help the brain and device communicate – only have partial capabilities. Northwestern Medicine scientists have developed a method that helps people with severe paralysis regain their grasping function.
“Most BMIs to date have concentrated on the position or velocity of the hand and fingers,” said Marc Slutzky, assistant professor in the Ken and Ruth Davee Department of Neurology, Physiology and Physical Medicine and Rehabilitation.
However, those BMIs lack the ability to control finger joint positions, making simple functions such as holding a hot cup of coffee nearly impossible. It is essential to grasp with the right amount of force to avoid dropping or crushing a cup, explained Dr. Slutzky.
So, how does it work? Traditional BMIs translate electric signals recorded from the brain. Using electrodes attached to the scalp or implanted in the brain, they pass over the injured part of the nervous system that causes paralysis.
Dr. Slutzky and his lab focused on recording signals from subjects using subdural electrodes, which are placed below the tissue that covers the brain. Using these different signals, they were able to decode the force and finger muscle activity levels that the subjects exerted while pinching a sensor between their thumb and index finger.
Subdural electrodes are less invasive than those implanted in the brain itself, and they may also be recorded for longer periods of time.
Dr. Slutzky and his team discovered that subdural signals provide a remarkable amount of information about grasp force and underlying muscle activity. Ultimately, this information can be applied to BMI technology to help people paralyzed from neurological disorders such as stroke or spinal cord injury.