Neuroscientists have developed a brain-machine interface (BMI) that allows primates to use only their thoughts to navigate a robotic wheelchair.
The BMI uses signals from hundreds of neurons recorded simultaneously in two regions of the monkeys’ brains that are involved in movement and sensation. As the animals think about moving toward their goal—in this case, a bowl of fresh grapes—computers translate their brain activity into real-time operation of the wheelchair.
The interface could one day help people with disabilities who have lost most muscle control and mobility due to quadriplegia or ALS, says senior author Miguel Nicolelis, co-director of the Center for Neuroengineering at Duke University.
“In some severely disabled people, even blinking is not possible,” he says. “For them, using a wheelchair or device controlled by noninvasive measures like an EEG (a device that monitors brain waves through electrodes on the scalp) may not be sufficient. We show clearly that if you have intracranial implants, you get better control of a wheelchair than with noninvasive devices.”
Scientists began the experiments in 2012, implanting hundreds of hair-thin microfilaments in the premotor and somatosensory regions of the brains of two rhesus macaques. They trained the animals by passively navigating the chair toward their goal, the bowl containing grapes.
During this training phase, the scientists recorded the primates’ large-scale electrical brain activity and then programmed a computer system to translate brain signals into digital motor commands that controlled the movements of the wheelchair.
As the monkeys learned to control the wheelchair just by thinking, they became more efficient at navigating toward the grapes and completed the trials faster.
In addition to observing brain signals that corresponded to translational and rotational movement, the researchers also discovered that primates’ brain signals showed signs they were contemplating their distance to the bowl of grapes.
“This was not a signal that was present in the beginning of the training, but something that emerged as an effect of the monkeys becoming proficient in this task,” Nicolelis says. “This was a surprise. It demonstrates the brain’s enormous flexibility to assimilate a device, in this case a wheelchair, and that device’s spatial relationships to the surrounding world.”
As reported in Scientific Reports, the trials measured the activity of nearly 300 neurons in each of the two monkeys. Researchers previously reported the ability to record up to 2,000 neurons using the same technique. The team now hopes to expand the experiment by recording more neuronal signals to continue to increase the accuracy and fidelity of the primate BMI before seeking trials for an implanted device in humans, Nicolelis says.
The National Institutes of Health funded this study. The Itau Bank of Brazil provided research support to the study as part of the Walk Again Project, an international non-profit consortium aimed at developing new assistive technologies for severely paralyzed patients. The authors declared no competing financial interests.
Source: Duke University