Amputee Monkeys Control Robotic Arm With Their Minds


Tom Hale

Tom is a writer in London with a Master's degree in Journalism whose editorial work covers anything from health and the environment to technology and archaeology.

Senior Journalist

Nicho Hatsopoulos in his robotics lab at the University of Chicago. Jean Lachat

The melding of monkey minds and machine has begun.

A team of neuroscientists at the University of Chicago has developed a robotic arm that rhesus monkey amputees can control through their thoughts. This mind-blowing research was recently published in the journal Nature Communications


The three monkeys used in this study had had one arm amputated numerous years ago (not for the purposes of the study). Most incredibly of all, the scientists noted that the monkeys' brains actually began to create new neural connections after 40 days of learning how to use the robotic arm. Not only is this a great demonstration of brain plasticity, it also highlights how machines could become incorporated into the “wiring” of organic brains.

“That’s the novel aspect to this study, seeing that chronic, long-term amputees can learn to control a robotic limb,” lead author Nicho Hatsopoulos, professor of organismal biology and anatomy, said in a statement. “But what was also interesting was the brain’s plasticity over long-term exposure, and seeing what happened to the connectivity of the network as they learned to control the device.”

This robotic arm is being controlled by a monkey. Jean Lachat

The monkeys were conditioned with the reward of sweet juice to move a robotic arm and grasp a squidgy ball using only their thoughts. Two of the monkeys had the electrode implanted in the side of the brain opposite, or contralateral, to the amputated limb. The third animal had electrodes implanted ipsilaterally, on the same side as the amputated limb.

Using electrodes to register the activity of neurons in the brain, the scientists gradually saw the patterns of activity change as the monkeys began to master the new skill. The brains of the monkeys with contralateral electrodes saw certain portions of neurons “grow” in density as training progressed.


But the researchers observed something even more incredible in the brain of the monkey with an ipsilateral electrode. The connections here were already dense at the beginning of the experiment since the monkey was readily using its arm on that side. First, the neurons in this area were trimmed, then they were gradually rebuilt into a denser network.

“That means connections were shedding off as the animal was trying to learn a new task because there is already a network controlling some other behavior,” added study author Karthikeyan Balasubramanian. “But after a few days, it started rebuilding into a new network that can control both the intact limb and the neuroprosthetic.”

Comparison of network density between the contralateral and ipsilateral monkeys during training. University of Chicago


  • tag
  • brain,

  • robotics,

  • neurons,

  • monkey,

  • robot,

  • amputee,

  • transhumanism,

  • brain plasticity,

  • rhesus monkey,

  • machine mind