Scientists recorded brain activity as monkeys learned to steer wheelchairs by thinking.
Image credit: Miguel Nicolelis/Duke Center for Neuroengineering
Severe paralysis resulting from a spinal cord injury or conditions such as cerebral palsy or a stroke can leave some people unable to even blink. Incredible advances in assistive technology have enabled individuals who would previously been hindered by their condition to live a full life.
The well-known scientist, Stephen Hawking, is a prime example. Hawking, who has motor neuron disease, communicates using movement in his cheek. An infrared switch, mounted on his spectacles, detects the movement and allows him to interface with his computer. This enables him not only to speak, but also to participate in multiple activities.
Scientists have already developed wheelchairs that can be controlled with a noninvasive device such as an electroencephalogram (EEG). The EEG monitors activity in the brain through electrodes on the scalp that are connected to a computer.
In an attempt to provide for those who are the most severely affected, researchers have been experimenting since 2012 with intracranial implants, in the hope that these could offer better control.
Mapping movement through brain activity
The researchers first implanted hundreds of hair-thin microfilaments in the premotor and somatosensory regions of the brains of two rhesus macaque monkeys.
They then trained the monkeys by passively navigating the chair toward their goal, in this case, a bowl of grapes.
By recording the primates' large-scale electrical brain activity, the team was able to create a computer system that could translate brain signals into digital motor commands. This made it possible to control the movements of the wheelchair by thinking.
The brain-machine interface uses signals from hundreds of neurons recorded simultaneously in two regions of the brain that are involved in movement and sensation. As the animals think about moving toward their goal, computers translate their brain activity into real-time operation of the wheelchair.
In time, and with practice, the monkeys learned to control the wheelchair by thinking, and they were able to navigate with greater speed and efficiency toward the grapes.
The researchers were able to pinpoint the brain signals that corresponded to translational and rotational movement. They also noted from the monkeys' brain signals that they were considering how far they had to travel to reach the bowl of grapes.
Senior author Dr. Miguel Nicolelis, PhD, co-director for the Duke Center for Neuroengineering, says:
"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. 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."
The trials measured the activity of almost 300 neurons in each monkey.
In previous studies, Nicolelis' lab has recorded activity in up to 2,000 neurons using the same technique.
Next, the researchers hope that by recording increasing numbers of neuronal signals, they will be able to improve the accuracy and fidelity of the technique. After this, they hope to seek trials for an implanted device in humans.
Medical News Today reported last year that a man has been able to walk again using his own brainpower, following paralysis.