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Third Thumb

Prosthetic extra thumb alters how the brain represents the natural hand

10 February 2022

Third Thumb

We often ask for another pair of hands, but what would you do with an extra thumb? For a human to gain a useful appendage, we rely not only on technology, but also on our brain’s ability to learn and adapt. By adding a 3D-printed prosthetic to the hand of able-bodied volunteers and a quick training session, participants effectively carried out dexterous tasks like stirring coffee whilst holding the cup with the same hand. Impressive – but what’s going on in their brains? Volunteers quickly adapted to a new digit and used it without thinking about it, but scans revealed that the brain’s representation of fingers changed, with less of a distinction between them. Whether prosthetics like these were replacing lost function, or were an extension to our bodies, this shows how quickly our brains could adapt to future prosthetic technologies, but we must also consider their impact on the brain.

Written by Sophie Arthur

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BPoD stands for Biomedical Picture of the Day. Managed by the MRC Laboratory of Medical Sciences until Jul 2023, it is now run independently by a dedicated team of scientists and writers. The website aims to engage everyone, young and old, in the wonders of biology, and its influence on medicine. The ever-growing archive of more than 4000 research images documents over a decade of progress. Explore the collection and see what you discover. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.

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