Sensory and Motor Building Blocks of an Extra Robotic Digit Representation
- 1University of Cambridge
Abstract
Supernumerary limbs provide a unique opportunity to ask how the brain represents an entirely novel effector within an existing sensorimotor system. Here, we investigated how primary motor cortex (M1) represents a robotic extra digit (the Third Thumb; Dani Clode Design), and how this representation changes with experience. Using fMRI, we compared participants following short-term exposure with participants who had undergone longitudinal Third Thumb training. The device was controlled by the toes but operated alongside the biological fingers, while its sensory consequences were experienced on the hand. Following prolonged experience, greater activity was elicited in the M1 hand area both during Third Thumb control, and in response to its sensory consequences alone. Multivariate analyses showed that the Third Thumb representation became more distinct from its biological toe controller. Pattern component modelling further showed that the representation could be explained by a combination of its constituent motor and sensory patterns, but their relative contributions changed substantially with experience, from toe-dominated following short-term exposure to sensory-dominated following longitudinal training. These findings suggest that M1 can represent a novel effector through flexible recombination of existing sensorimotor representations, with experience altering how these pre-existing resources contribute to the emerging representation.
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BibTeX
@misc{dowdall2026sensory,
title = {{Sensory and Motor Building Blocks of an Extra Robotic Digit Representation}},
author = {L. Dowdall and E. Amoruso and G. Dominijanni and M. Molina-Sanchez and J. Diedrichsen and D. Clode and T. R. Makin},
howpublished = {bioRxiv},
year = {2026},
month = nov,
doi = {10.64898/2026.11.09.765353},
url = {https://www.biorxiv.org/content/10.64898/2026.11.09.765353v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Sensory and Motor Building Blocks of an Extra Robotic Digit Representation
AU - L. Dowdall
AU - E. Amoruso
AU - G. Dominijanni
AU - M. Molina-Sanchez
AU - J. Diedrichsen
AU - D. Clode
AU - T. R. Makin
PY - 2026
DA - 2026/11/09
PB - bioRxiv
DO - 10.64898/2026.11.09.765353
UR - https://www.biorxiv.org/content/10.64898/2026.11.09.765353v1
AB - Supernumerary limbs provide a unique opportunity to ask how the brain represents an entirely novel effector within an existing sensorimotor system. Here, we investigated how primary motor cortex (M1) represents a robotic extra digit (the Third Thumb; Dani Clode Design), and how this representation changes with experience. Using fMRI, we compared participants following short-term exposure with participants who had undergone longitudinal Third Thumb training. The device was controlled by the toes but operated alongside the biological fingers, while its sensory consequences were experienced on the hand. Following prolonged experience, greater activity was elicited in the M1 hand area both during Third Thumb control, and in response to its sensory consequences alone. Multivariate analyses showed that the Third Thumb representation became more distinct from its biological toe controller. Pattern component modelling further showed that the representation could be explained by a combination of its constituent motor and sensory patterns, but their relative contributions changed substantially with experience, from toe-dominated following short-term exposure to sensory-dominated following longitudinal training. These findings suggest that M1 can represent a novel effector through flexible recombination of existing sensorimotor representations, with experience altering how these pre-existing resources contribute to the emerging representation.
ER -