Six fingers per hand

Polydactyly is the extraordinary condition of someone who is born with more than five fingers or toes. In a case study published in Nature Communications, researchers from the University of Friborg, Imperial College London, Lausanne University Hospital and EPFL have for the first time examined the motor capacities and areas of the sensorimotor brain in people with polydactyly. The results show that an extra finger can greatly expand the abilities and handling skills. It allows people with six fingers to perform movements with one hand while those with only five fingers would need two hands. The increased motor abilities observed in polydactyl subjects are made possible by dedicated areas located in the sensorimotor brain areas. These findings could serve as a model for the development of additional artificial limbs extending motor abilities.

The case study of researchers from Freiburg, London and Lausanne studies for the first time the movement capabilities of six-fingered people by hand. In the case of the two subjects examined, an extra finger between the thumb and the index is fully formed on each hand. "We wanted to know if subjects have motor skills that go beyond five-fingered people and how the brain is able to control extra degrees of freedom," says Professor Carsten Mehring of the University of Friborg and Bernstein Center. from Friborg. .

To determine the extent of their abilities, the researchers asked the subjects to perform several behavioral experiments and their brain activity was monitored using functional magnetic resonance imaging (fMRI). The results show that the subjects' extra fingers are displaced by their own muscles. This allows the subjects to move their extra fingers as much as possible independently of all other fingers. "Our subjects can use their extra fingers independently, such as an extra inch, alone or with the other five fingers, which makes handling extremely versatile and skillful.For example, in our experiments, subjects can perform a task with one hand for which we normally need two hands, "sums up Professor Mehring. "Despite the extra finger increasing the number of degrees of freedom that the brain needs to control, we found no harm compared to five-fingered people.In a nutshell, it's amazing that the brain has enough capacity to do it without sacrificing anywhere else.That's exactly what our subjects do, "says Professor Etienne Burdet of Imperial College London.

To understand how the brain of subjects with polydactyly controls extra fingers, the scientist used high resolution functional magnetic resonance imaging (fMRI). "We found dedicated neural resources that control the sixth finger, and the motor and somatosensory cortex are organized to account for additional motor abilities observed," commented professors Andrea Serino and Michael Akselrod, who conducted the neuroimaging studies. at EPFL and Lausanne University Hospital.

Studying these hands polydactylically could advance the development of additional artificial limbs to develop people's motor skills. For example, an extra arm to help work alone in a tight environment or to allow a surgeon to perform operations without an assistant. However, scientists note that "extra extremities have been formed in subjects since birth.This does not necessarily mean that a similar functionality can be achieved when artificial limbs are completed later in life." People with polydactyly provide a unique opportunity to analyze additional limb neural control and sensorimotor skills opportunities. "