“What would you do with an extra thumb?” asks Dani Clode, the creator of the hand augmentation device called The Third Thumb. This hand extension is a 3D printed prosthetic that is controlled by the feet. The prosthetic is a project from the Plasticity Lab at the University of London which Clode is part of as a senior technical specialist and is inspired by ‘prosthesis’ which means ‘to add’ or ‘to put onto.’
With The Third Thumb, Clode is seeking answers to questions such as “can the human brain support an extra body part?” and, “how does the use of augmented technologies affect our bodies?” To get a lead in the artificial limb technology market, the Plasticity Lab is joining hands with the University of Cambridge this June 2022. With this collaboration, the hopes are to grow and learn more in the field of cognitive neuroscience.
Very excited to share the research video for our new published paper in Science Robotics, ‘Robotic hand augmentation drives changes in neural body representation’ @PlasticityUCL https://t.co/4WECT2YN4B
— Dani Clode (@DaniClode) May 20, 2021
The robotic digit
The Third Thumb is mounted on the right side of a hand and is moved by the big toe. The prosthetic is equipped with servomotors that are fitted on a wristband. This allows control of the flexion, extension, abduction, and adduction movements of the extra digit. Two pressure sensors are strapped underneath a participating individual’s big toe.
In an experimental study conducted by the lab, training the toe to control The Third Thumb was the primary step. The participants were trained in two groups where one group was given local anesthesia under a placebo. In comparison, the other group was taught without the placebo anesthesia.
If you’re controlling the #thirdthumb with your toes, what happens to your control over it if we anaesthetised them? Check out our new preprint! https://t.co/vEwuKq2ipy pic.twitter.com/cqKOnwk7v0
— Plasticity Lab (@plasticity_lab) May 24, 2021
Participants across both groups performed brilliantly without any significant difference. Many other tests that were applied revealed similar results that our brain has the capability for plasticity. They also did not observe any changes in the vitals of the participants during their 2-day experimental study.
Capacity for plasticity
We know that the left side of the brain controls the right side of the body and the right brain does the same for the left side of the body. But neuroscientist V. S. Ramachandran discovered more than what we know. In his book called The Tell-Tale Brain, Ramachandran describes a peculiar case of one of his amputee patients. The complaint of his patient was that their right “phantom hand” still ached.
To his surprise, Ramachandran found that the left side of the face has an entire neuronal map drawn of a person’s right hand. In order to rid his patient of the pain, he made the patient put the non-amputated hand in front of a mirror and the other arm behind it. They were asked to flex, extend, adduct, and abduct their left hand and observe the mirror image. By observing the lateral image in the mirror, the person felt that their right hand or the phantom hand also moved and was relieved of the pain.
This story merely suggests that the brain is capable of adjusting to new or unexpected situations with a little bit of both – nature and nurture. The Third Thumb project on using a hand augmentation device has the potential to help us know more about the brain and how it functions.
YouTube: Why I Created a Third Thumb | Dani Clode | TEDxVienna
Photo credits: The feature image has been taken by Marco Bianchetti.