Neurotechnology attempts to develop supernumerary limbs, but can the human brain deal with the complexity to control an extra limb and yield advantages from it? Here, we analyzed the neuromechanics and manipulation abilities of two polydactyly subjects who each possess six fingers on their hands. Anatomical MRI of the supernumerary finger (SF) revealed that it is actuated by extra muscles and nerves, and fMRI identified a distinct cortical representation of the SF. In both subjects, the SF was able to move independently from the other fingers. Polydactyly subjects were able to coordinate the SF with their other fingers for more complex movements than five fingered subjects, and so carry out with only one hand tasks normally requiring two hands. These results demonstrate that a body with significantly more degrees-of-freedom can be controlled by the human nervous system without causing motor deficits or impairments and can instead provide superior manipulation abilities.
Bibliographical noteFunding Information:
We thank the subjects of this study for their availability and flexibility. We thank Tomoki Arichi, Glauco Caurin, Sofia Dall’Orso, Ana Dos Santos Gomes, Jonathan Eden, Alessandro Farnè, Dollyane Muret, Luca Rosalia and Marco Solca for technical assistance. We thank Claudia Clopath, Nicolas Rojas and Stephen Scott for comments on an earlier version of this manuscript and Dmitry Kobak for comments on parts of the analyses. This research was funded in part by the German Research Foundation (DFG) through grants no INST 39/1014-1 and INST 39/963-1, the state of Baden-Württemberg through bwHPC and the Struktur-und Innovationsfonds (SI-BW), the Swiss National Science Foundation (PP00P3_163951 / 1), by EU FP7 grants PEOPLE-ITN-317488-CONTEST, ICT-611626 SYMBITRON, H2020 ICT-644727 COGIMON, Minded Program—Marie Skłodowska-Curie grant agreement no. 754490 and by the grant UK EPSRC MOTION EP/NO29003/1.
© 2019, The Author(s).
ASJC Scopus subject areas
- Chemistry (all)
- Biochemistry, Genetics and Molecular Biology (all)
- Physics and Astronomy (all)