Do you think you could get used to a working third inch? Like in a second thumb on one of your hands. The idea sounds ridiculous, right? Researchers have one Third thumb prosthetic appendage and soon discovered that our brains actually change to adapt to it. It̵
Designer Dani Clode originally developed the Third Thumb device as part of a graduation project to reimagine how people view prosthetic appendages. Rather than focusing on the loss of a human body part, the third thumb focuses an eye on enlarging the body.
Professor Tamar Makin, who leads a neuroscience team at UCL that is investigating how the brain can adapt to body enlargement, took note of the Third Thumb device and asked Clode to join the project. For several days, the researchers trained people to wear the Third Thumb and use it for everyday tasks, such as picking objects. Other people acted as controls, wearing a static version of the thumb.
The third thumb is a 3D printed appendage that the user wears on the side of the little finger; it can be adjusted to work for both hands. Users operate the thumb with two pressure-sensitive sensors attached to the underside of their big toes. The sensors connect wirelessly to the thumb and different pressure levels allow for different movements.
The third thumb allowed subjects to perform tasks such as holding a mug with the thumb while stirring coffee with the same hand. Or wear more glasses than they could have without a thumb. Users quickly mastered the basic tasks, both in lab tests and in the wild. The subjects even performed tasks while distracted, such as moving building blocks while doing math or wearing a blindfold.
We know from scans that the brain builds a representation of the individual fingers on a hand. Researchers scanned a number of users before and after life with the extra thumb, even comparing the hand with the thumb to the hand without. During the fMRI, the participants moved their fingers, although they could not wear the third thumb for safety reasons.
Researchers found that the brain’s perception of those fingers changed after wearing and using the thumb long enough. While before the study began, the subjects’ brain activity showed different representations of the individual fingers, those representations started to blur after working with the third thumb. After a week without the third inch, brain activity returns to normal, suggesting the change may be permanent. But without lengthy testing, it’s unclear how long the brain can hold on to the changes.
It’s also not clear what that means for long-term enlargement of bodies. The study shows that the brain changed and adapted to a new appendage, and in a way that we don’t see when using a screwdriver or other tools. That could change how we approach prosthetics meant to replace a limb and raise questions about augmentation.
Like the study paper Put it this way: “Importantly, however, such a successful human-robot integration may have implications for some aspect of body representation and motor control that require further consideration and investigation.”
Source: Plasticity Lab