Study Shows There Are Surprising Benefits to Having an Extra Finger
Polydactyly may prove much more useful than previously thought.
By Daisy Hernandez
C. Mehring et al., Nature
A recent study revealed that people born with fully developed extra fingers are more dextrous than people born with the standard five digits per hand.
Study subjects, a mother and son each with six fingers per hand, were able to tie shoe laces single-handedly and use regular video game controllers with ease.
The study may serve researchers who are investigating the development and usability of robotic limbs.
A new study shows that people who have six fully-formed fingers on one hand may not be at a disadvantage, but rather, have more dexterity than people with five fingers per hand.
In fact, the two people (a mother and son) who were part of the study have six fingers on each hand and are able to "type on their phones, play complicated video games, and even tie a shoelace all with just one hand," reports Science Alert.
Polydactyly—having extra fingers and/or toes—is usually treated at birth by surgically removing the extra digits. Because this mutation is often removed very early in life, there have been few chances to research what benefits being polydactyl may afford those with supernumerary fingers (SF).
An MRI showed researchers that the SF in each subject were "actuated by extra muscles and nerves" and an fMRI revealed "a distinct cortical representation of the SF." This means that the brain didn't have to work harder or pull resources from other areas that controlled other body parts or hand and finger muscles; the extra fingers had their own space in the subjects' brains that moved them.
Additionally, the study shared that each subject was able to move the SF "independently from the other fingers," allowing for even more dexterity.
Researchers are curious about what we can learn from people with SF and how that knowledge can be translated into the development and functionality of robotic limbs and digits. However, challenges include the fact that robotic limbs will not have the same complex neural structure, tendons, and muscle groups as the SF in humans.
"Polydactyly individuals with functional SF offer a unique opportunity to investigate the neural control of supernumerary limbs, analyze internal representations of the body and the limits of sensorimotor capabilities in humans," said the study authors.
Another challenge in using the data from polydactyl subjects to explore robotic limb options is that people with extra digits are accustomed to using their SF because they were born with them. A person who receives an extra robotic limb may never achieve the same level of dexterity and range of use.
"In our study, the extra digits have been trained in the subjects since birth. This does not necessarily mean that similar functionality can be achieved when artificial limbs are added on later in life," said lead study author, Dr. Carsten Mehring from the University of Freiburg.
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