One in 500 people are born with polydactyly, extra fingers or toes. Researchers at University of Freiburg in Germany, Imperial College London and Université de Lausanne / EPFL in Switzerland studied two people with well-formed usable sixth fingers between the thumb and first fingers on both hands to understand how their brains deal with the "extra workload" of controlling those digits. According to Imperial College bioengineer Etienne Burdet, high-resolution functional magnetic resonance imaging (fMRI) revealed that "the polydactyl individual's brains were well adapted to controlling extra workload, and even had dedicated areas for the extra fingers. It's amazing that the brain has the capacity to do this seemingly without borrowing resources from elsewhere." From Imperial College London:
Polydactyl participants also performed better at many tasks than their non-polydactyl counterparts. For instance, they were able to perform some tasks, like tying shoelaces, with only one hand, where two are usually needed... (See video above.)
The international team of authors say the findings might serve as blueprint for the developing artificial limbs and digits to expand our natural movement abilities. For example, giving a surgeon control over an extra robotic arm could enable them to operate without an assistant...
However, (lead author Carsten Mehring of Freiburg University) warned that people with robotic extra limbs may not achieve as good control as observed in the two polydactyl subjects. Any robotic digits or limbs wouldn’t have dedicated bone structure, muscles, tendons or nerves.
In addition, subjects would need to learn to use extra fingers or limbs, much like how an amputee learns how to use a prosthetic arm.
Professor Mehring added: "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."
"Augmented manipulation ability in humans with six-fingered hands" (Nature Communications)