Monkeys control wheelchairs with thought

A recently developed brain-machine interface (BMI) allows monkeys to control and navigate a robotic wheelchair using only their thoughts. This project was conducted by a group of neuroscientists at Duke Health and published in the March 3 issue of Scientific Reports. It focuses specifically on hundreds of neurons in two regions of the brain that are involved in movement and sensation.

The experiment was carried out utilizing a food incentive: A bowl of fresh grapes. As the primates thought about moving toward the bowl of grapes, computers were able to translate their brain activity into real-time operation of a wheelchair.

The project began in 2012 with scientists implanting hundreds of hair-thin microfilaments into the premotor and somatosensory regions of the brains of two rhesus macaques. While scientists recorded the primates’ large-scale electrical brain activity, the monkeys were trained to navigate the chair toward their goal — the bowl of grapes. A computer system was then programmed to translate their brain signals into digital motor commands that controlled the actual movements of a wheelchair.

More specifically the two monkeys were chronically implanted with multichannel microelectrode arrays. These arrays allowed for wireless recordings from different neurons in the premotor and sensorimotor cortical areas. The first trial consisted of the monkeys remaining seated in their robotic wheelchairs while passive navigation was done to train a linear decoder and extract 2-D wheelchair kinematics from the activity of their brains.

The next trial consisted of monkeys employing the wireless BMI to translate cortical activity into the robotic wheelchair’s translational and rotational velocities. The researchers found that the navigation to the goal (the bowl of grapes) was due to activation of a population of cortical neurons tuned to whole-body displacement. These results particularly prove that intracranial BMIs could be used to restore whole-body mobility for severely paralyzed patients in the near future.

According to Miguel Nicolelis, co-director of the Duke Center for Neuroengineering, the monkeys learned to control the wheelchair just by thinking when given time and extensive training. Eventually they became more and more efficient at navigating towards their goal and were able to complete trials in less time.

Furthermore Nicolelis said that the studies proved that brain signals were related not only to translational and rotational movements but also to the monkeys’ distance from the bowl of grapes. This meant that the primates were able to contemplate the distance from their goal and adjust their thoughts accordingly.

“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 said in a press release. “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.”

Following the trials that measured the activity of nearly 300 neurons in the two monkeys, the team plans to expand their experiment in order to record more neural signals. Furthermore, the team will experiment on increasing the accuracy of the primate BMI before looking to do any trials on humans.

Nevertheless, Nicolelis said that the study has tremendous implications for people with disabilities who have lost control of their muscles due to quadriplegia or Amyotrophic Lateral Sclerosis (ALS).

Up to this point, only noninvasive BMI approaches, mostly based on Electroencephalography (EEG), have enabled direct brain control over wheelchair navigation. Few studies have previously attempted to apply Nicolelis’s intracranial BMI approach to wheelchair control.

“In some severely disabled people, even blinking is not possible,” Nicolelis said. “For them, using a wheelchair or device controlled by noninvasive measures like an EEG may not be sufficient. We show clearly that if you have intracranial implants, you get better control of a wheelchair than with noninvasive devices.”