The sense of touch is crucial when using our hands. However, until recently there were no brain-controlled prosthetic limbs created for medical use.
In a new study, microelectrode arrays were implanted into the primary somatosensory cortex of a person with spinal cord injury and generated sensations of touch that were perceived as coming from his own paralyzed hand. The impulses feel like pressure, can be controlled in intensity and are stable for months. The study, published online in Science Translational Medicine, was developed by a team of scientists led by Robert Gaunt, assistant professor of physical medicine and rehabilitation at the University of Pittsburgh.
The study was able to show how a 28-year-old patient, Nathan Copeland, who came out of brain surgery after a car accident, had the sensation of touch through this robotic arm controlled by his brain.
"The most important result in this study is that microstimulation of sensory cortex can elicit natural sensation instead of tingling," explained study co-author and professor of neurobiology Andrew B. Schwartz. According to him, more research should be conducted for a more in-depth understanding of the stimulation patterns that would help the subjects conduct more precise movements.
More attempts were previously conducted. In 2012, one of the study co-authors, Jennifer Collinger, assistant professor and research scientist, and her team helped a patient with quadriplegia. Before that, another paralyzed subject, who survived a terrible accident, managed to touch hands with his significant other.
However, what makes the research more difficult is the type of feedback received from each stimulus. Whenever touching is involved, we don't only coordinate our muscles through our brains, but we do it through the constant feedback we receive from the objects we're touching, their consistency and shape. This relation is hugely important, as it suggests a specific type of movement to the brain.
Gaunt and his team managed to develop a system where the inputs from the robotic arm are carried through a microelectrode system implanted in the part of the brain where the neural activity connected to hand movement is located.
Back in 2004, after Copeland's car accident, the quadriplegia causing him the impossibility to feel anything below the upper chest forced him to drop out of college. In the spring of 2015, he re-entered the operating room after passing the entire procedure to qualify him for this operation. Approximately a month after the surgery, the patient was happy to feel about every finger of his robotic hand.
From control of movement to the creation of the robotic arm, the long-term study proved that this direction could be worthy of further investment and scientific interest.