Phantom-limb pain is a condition in which amputees feel like their amputated limb is still attached to their bodies. While its cause is unknown, reports say that 50-80% of cases are painful. Currently, with no established treatment, the condition can negatively impact the quality of life for recovering amputees.
One theory that may explain how the condition works is that even after amputation, the brain's areas that used to control the limb remain strongly connected to the mental image of the limb. To weaken the connection, researchers from Osaka University in Japan hypothesized that it might be able to train the brain regions that control intact limbs to control the phantom limb as well.
To do so, the researchers recruited 12 patients with chronic phantom limb pain and instructed them to use a brain-computer-interface to interact with a virtual hand. While six randomly selected patients actually controlled the virtual hand with their brain activity, for the other six, the virtual hands moved independently of their brain activity. Throughout the experiment, all patients nevertheless thought they were controlling the virtual hand and trained for roughly 30 minutes per day over three days.
After the three-day trial, each patient was asked to rate their phantom limb pain. In total, the researchers found that phantom limb pain reduced by 30% even after the first day of training for those who really controlled the virtual hand, and lasted for up to five days after the final day of training. The researchers also noted that their mental image of having a phantom hand also weakened.
"These findings are promising, especially given that alternatives like mirror training require a month of training to have the same effect. However, in order for this treatment to become truly practical, the cost must be reduced." says Takfumi Yanagisawa, lead author of the study.