Mind controlled limbs, a big hope for amputees

Amputees can learn to control a robotic arm with their mind even several years after an amputation, through electrodes implanted in the brain, according to a study led by an Indianorigin scientist. Researchers at the University of Chicago in the US showed that the areas of the brain used to control the amputated limb and the remaining, intact limb can create new connections to learn how to control the device. “That is the novel aspect to this study, seeing that chronic, long-term amputees can learn to control a robotic limb,” said Nicho Hatsopoulos, professor at University of Chicago. “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,” said Hatsopoulos, senior author of the study published in the journal Nature Communications. Previous experiments have shown how paralysed human patients can move robotic limbs through a brain machine interface. The study is one of the first to test the viability of these devices in amputees as well. Researchers worked with three rhesus monkeys who suffered injuries at a young age and had to have an arm amputated to rescue them four, nine and 10 years ago respectively. In two of the animals, they implanted electrode arrays in the side of the brain opposite, or contralateral, to the amputated limb. This is the side that used to control the amputated limb. In the third animal, the electrodes were implanted on the same side, or ipsilateral, to the amputated limb. This is the side that still controlled the intact limb. The monkeys were then trained to move a robotic arm and grasp a ball using only their thoughts.

The connections between neurons on the contralateral side - the side that had been controlling the amputated arm – were sparse before the training. However, as training progressed, these connections became more robust and dense in areas used for both reaching and grasping.