It turns out humans are a dab hand at using a robotic "third thumb", suggests a recent experiment that saw people learning to use a specially designed robotic extra thumb. Not only did they master the use of the extra thumb with surprising ease, but scans also showed their brain had quickly adapted to manage the new skill.
The study by neuroscientists at University College London (UCL) was published in the journal Science Robotics this week.
"Evolution hasn't prepared us to use an extra body part, and we have found that to extend our abilities in new and unexpected ways, the brain will need to adapt the representation of the biological body," Professor Tamar Makin, lead study author from the UCL Institute of Cognitive Neuroscience, said in a press release.
The "Third Thumb" started as a design project by Dani Clode while studying at the Royal College of Art in London. The 3D-printed digit is worn on the side of the hand opposite the user's actual thumb, near the pinky finger. It’s controlled using a wireless pressure sensor attached to the underside of the foot. The user simply applies a small amount of pressure under their big toe and the extra thumb will contract, allowing them to grasp objects.
In the new research, 20 people were trained to use the thumb over five days. They were also encouraged to wear the thumb at home and use it to complete their day-to-day tasks, totaling two to six hours of wear time per day. Another 10 control participants were given the same plan, but wore a static extra thumb instead.
By the end of the training, participants were able to perform a range of dexterous tasks, such as picking up a bunch of balls and wine glasses. They were even able to complete tasks blindfolded or distracted.
The researchers then looked at the participants' brains using an fMRI scanner while they moved around their fingers individually. The scans picked up on a small but significant change to the way the hand movement was represented in the brain's sensorimotor cortex. Furthermore, the brain activity pattern corresponding to each individual finger became more similar in the participants trained with the moving extra thumb.
However, these changes were only fleeting. One week later, the participants were called back to the lab and further scans revealed that the changes in their brain's hand area had subsided.
The findings demonstrate the brain's remarkable plasticity and suggest we're remarkably capable of adapting to technological extensions of the physical body. In the not too distant future, when high-tech body augmentation becomes widely available, this could be a very useful skill to possess.
"Body augmentation is a growing field aimed at extending our physical abilities, yet we lack a clear understanding of how our brains can adapt to it. By studying people using Dani's cleverly-designed Third Thumb, we sought to answer key questions around whether the human brain can support an extra body part, and how the technology might impact our brain,” Professor Makin added.