How does the brain adapt to technical expansions? Researchers have investigated this using the example of a robotic additional thumb. Test subjects quickly learned how to use the gripping tool skilfully and creatively and ultimately even felt the third thumb to be part of their own body. This was accompanied by characteristic changes in the representation of the hand in the brain, studies have shown. Further investigations should now clarify whether this could have a negative effect on normal body control.
When gripping the coffee cup, operating the computer keyboard or playing the guitar – a sophisticated neural control system enables the movements of our fingers and other parts of the body. The basis is an image of our body and its moving elements in the brain. In this context, the new techniques of so-called augmentation now raise questions: More and more sophisticated robotic systems are being developed that can replace the functions of lost body parts or expand human capabilities. “Body augmentation is a growing area, but we still lack a clear understanding of how well and safely our brain can adapt to these systems,” says Tamar Makin of University College London.
As part of a study, she and her colleagues have now examined the effects of an augmentation device that was developed by co-author Danielle Clode at the Royal College of Art. The so-called third thumb is worn on the side of the dominant hand – near the little finger so that it is opposite the user’s actual thumb. The wearer controls it with pressure sensors that are attached to the feet, on the underside of the big toes. The two toe sensors are wirelessly connected to the third thumb and allow different movements. “By studying people who use this third thumb, we wanted to investigate the extent to which the human brain can support such an additional body part and how the technology affects our brain,” says Makin.
“Feels like part of the body”
20 volunteers took part in the study, who learned how to use the third thumb both under the guidance of the researchers and in everyday life: within five days, they used the additional robotic finger for a total of six hours a day. During the training in the laboratory, the participants received basic training in how to use the thumb. The focus was on tasks that required cooperation between the hand and the additional technical finger, such as picking up several balls or wine glasses with one hand. At home, the test subjects were able to let their creativity run free when using the device.
It was found that they could quickly develop motor control and skillful hand-thumb coordination. The scientists report that less and less concentration was required. “Our study shows that people can quickly learn to control an augmentation device and use it to their advantage without having to think too much. We saw that the subjects changed their natural hand movements when they used the third thumb, and they also reported that the robotic thumb ended up feeling like part of their own body, ”says Clode.
Critically altered brain activity?
In order to track down possible effects on brain functions, the researchers used functional magnetic resonance imaging (fMRI) to examine the subjects’ brain activity before and after they got used to the device. Without wearing their third thumb, the participants moved their fingers one at a time on both hands. The evaluations showed that there were significant changes in how the hand that had been extended with the third thumb was represented in the sensorimotor cortex of the brain. “Evolution did not prepare us to use an additional body part. It now shows how the brain has to adapt the representation of the biological body in order to expand our capabilities, ”says Makin.
However, when fMRI examinations were repeated one week after the end of the period of use, the changes in brain activity disappeared again, the scientists report. At least during the short period of acclimatization of five days, the effects were apparently not permanent. Nevertheless, the result raises critical questions that should be clarified before the technology can be used widely, say the researchers: In future studies, they now want to investigate to what extent the changed representation of the hand in the brain could negatively affect normal use of the hand.
“Augmentation devices similar to the one we tested could prove useful because they enable people to perform complex tasks permanently or temporarily with just one hand. For example, surgeons could do without assistants or factory workers could work more efficiently. But first we have to research further into the questions of how these devices interact with our brain, ”says first author Paulina Kieliba from University College London. “We have to make sure that augmentation devices make the best possible use of our brain’s ability to learn and adapt, while at the same time ensuring that they can be used safely,” concludes the neuroscientist.
Source: University College London, Article: Science Robotics, doi: 10.1126 / scirobotics.abd7935
Video: Dani Clode Design and The Plasticity Lab, UCL