image: During training, MEG signals were recorded while patients watched the images of the phantom hand that was controlled by real-time decoding of the recorded MEG signals. view more
Credit: Osaka University
Osaka, Japan — Phantom-limb pain is as mysterious as the name implies. The vast majority of amputees experience "phantom-limb" sensations that make them feel their missing limb is still part of their body. The cause is still unknown, and 50% to 80% of the cases, the sensations are painful. With no established treatments or medication, phantom-limb pain can have a large impact on the quality of life and recovery for amputees.
Although the cause is unknown, one theory is that it happens when areas of the brain that used to control the amputated limb remain strongly connected to the mental image of the limb. To weaken this connection, one idea is to train the brain regions that control the intact limb to also control the phantom limb. Takufumi Yanagisawa and his team at Osaka University hypothesized that the key to accomplishing this was to do it unconsciously.
"It is very difficult to intentionally activate the part of your brain that controls your right hand without actually thinking about moving that hand," explains Yanagisawa. "Instead, we designed a system in which the patients did not even know they were using those parts of their brains."
In order to train the brains of patients with phantom-hand pain, the group used a brain-computer-interface. First they recorded brain activity when patients opened and closed their intact hands and used the pattern of brain activity as a template. Then they continuously recorded brain activity related to the intact hands, but asked the patients to try to control a virtual hand with their phantom hand. For half the experiments, this training was real; the recorded brain activity was decoded based on the template and the image of the opening/closing virtual hand was adjusted accordingly. For the other half, the images of the virtual hand were randomly adjusted with no connection to brain activity. All patients thought they were actually controlling the virtual hand. Patients trained for about 30 min/day for 3 days, and after each session they rated the intensity of their phantom-limb pain.
The team found that pain was reduced by 30% even on the first day of training and the effect lasted up to five days after training was complete. Importantly, only patients who received real training reported less phantom pain. They also found that after training, the mental image of the phantom hand was weakened in the brain regions that once controlled the amputated hand.
"These findings are promising," says Yanagisawa, "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."
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The article, "BCI training to move a virtual hand reduces phantom limb pain: A randomized crossover trial," was published in Neurology at DOI: https://doi.org/10.1212/WNL.0000000000009858
About Osaka University
Osaka University was founded in 1931 as one of the seven imperial universities of Japan and is now one of Japan's leading comprehensive universities with a broad disciplinary spectrum. This strength is coupled with a singular drive for innovation that extends throughout the scientific process, from fundamental research to the creation of applied technology with positive economic impacts. Its commitment to innovation has been recognized in Japan and around the world, being named Japan's most innovative university in 2015 (Reuters 2015 Top 100) and one of the most innovative institutions in the world in 2017 (Innovative Universities and the Nature Index Innovation 2017). Now, Osaka University is leveraging its role as a Designated National University Corporation selected by the Ministry of Education, Culture, Sports, Science and Technology to contribute to innovation for human welfare, sustainable development of society, and social transformation.
Website: https://resou.osaka-u.ac.jp/en/top
Journal
Neurology