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The neural resource allocation problem when enhancing human bodies with extra robotic limbs


The emergence of robotic body augmentation provides exciting innovations that will revolutionize the fields of robotics, human–machine interaction and wearable electronics. Although augmentative devices such as extra robotic arms and fingers are informed by restorative technologies in many ways, they also introduce unique challenges for bidirectional human–machine collaboration. Can humans adapt and learn to operate a new robotic limb collaboratively with their biological limbs, without restricting other physical abilities? To successfully achieve robotic body augmentation, we need to ensure that, by giving a user an additional (artificial) limb, we are not trading off the functionalities of an existing (biological) one. Here, we introduce the ‘neural resource allocation problem’ and discuss how to allow the effective voluntary control of augmentative devices without compromising control of the biological body. In reviewing the relevant literature on extra robotic fingers and arms, we critically assess the range of potential solutions available for this neural resource allocation problem. For this purpose, we combine multiple perspectives from engineering and neuroscience with considerations including human–machine interaction, sensory–motor integration, ethics and law. In summary, we aim to define common foundations and operating principles for the successful implementation of robotic body augmentation.

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Fig. 1: Body enhancement continuum with respect to bodily ability.
Fig. 2: Examples of use case scenarios of body augmentation with XRLs.
Fig. 3: Taxonomy for XRAs and XRFs and a comparison with established robotics paradigms.
Fig. 4: Possible interfaces for control and sensory feedback for an XRA.


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G.D. was funded by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 813713). S.S. was funded by the CHRONOS project, the Wyss Center for Bio and Neuroengineering and the Bertarelli Foundation. F.D.V. was funded by ANR grants nos. ANR-17-EURE-0017 FrontCog and ANR-16-CE28-0015 Developmental tool. T.R.M. was funded by an ERC Starting Grant (715022 EmbodiedTech) and a Wellcome Trust Senior Research Fellowship (grant no. 215575/Z/19/Z). G.S. and D.P. were supported by Progetto Prin 2017 ‘TIGHT: Tactile InteGration for Humans and arTificial systems’, protocol 2017SB48FP. S.M. was funded by the Swiss National Science Foundation through the National Centre of Competence in Research (NCCR) Robotics, the ERC under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 813713) and the Bertarelli Foundation.

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G.D. and S.S. contributed equally to writing, editing and the overall vision of the paper, and also the figures. They and T.M. wrote the introductory section. G.S. and S.R. wrote the ‘Sensory feedback for XRAs and XRFs’ section. E.P. and F.D.V. wrote the ‘Regulatory, legal and ethical considerations’ section, and A.d’A. and D.P. wrote the ‘Motor control of XRAs and XRFs’ section. T.R.M. and S.M. wrote the final section. S.B. contributed to the editing of the paper, including reformulating of conceptual content. A.d’A., T.R.M., D.P. and S.M. contributed equally to the overall structure and the underlying idea of the review. All authors reviewed the manuscript.

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Correspondence to Silvestro Micera.

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Dominijanni, G., Shokur, S., Salvietti, G. et al. The neural resource allocation problem when enhancing human bodies with extra robotic limbs. Nat Mach Intell 3, 850–860 (2021).

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