iiinova — where your digital self keeps evolving

Lucy Dowdall @lucydowdall.bsky.social · 27/06/2025

Catching up with the community at UK Sensorimotor is always a highlight of the year! Thanks for having us @uksensorimotor25.bsky.social @ox.ac.uk !

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Lucy Dowdall @lucydowdall.bsky.social · 19/06/2025

Check out the full pre-print now: doi.org/10.1101/2025.06.16.658246. This work was truly a collaborative and interdisciplinary effort, and we’d like to thank all of our collaborators, and the over 100 participants that made this work possible! @plasticity-lab.bsky.social

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Lucy Dowdall @lucydowdall.bsky.social · 19/06/2025

Finally, we not only found increased subjective somatosensory embodiment following Third Thumb training, but this increase also correlated with increased similarity between the Third Thumb and biological fingers in S1

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Lucy Dowdall @lucydowdall.bsky.social · 19/06/2025

Within the S1 hand representation, we saw experience-dependent refinement of the Third Thumb’s sensory representation following training, as it became more similar to the biological fingers in a way not seen for our control group

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Lucy Dowdall @lucydowdall.bsky.social · 19/06/2025

Following Third thumb training, markerless hand tracking revealed reduced co-usage amongst the biological fingers as the Third Thumb became integrated into the hand’s coordination patterns

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Lucy Dowdall @lucydowdall.bsky.social · 19/06/2025

To explore how sensorimotor experience refines this representation, participants then underwent 7 days of motor training involving Third Thumb-biological hand collaboration, or our control group instead trained to play the piano keyboard

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Lucy Dowdall @lucydowdall.bsky.social · 19/06/2025

Using RSA, we found the immediate emergence of a topographically organised Third Thumb sensory representation within S1. This representation is also distinct from the biological palm representation

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Lucy Dowdall @lucydowdall.bsky.social · 19/06/2025

But how does the brain then represent this natural sensory information? We next stimulated the Third Thumb and the biological hand, and used fMRI to map their sensory representations in primary somatosensory cortex

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Lucy Dowdall @lucydowdall.bsky.social · 19/06/2025

Despite the tasks being designed for the artificial systems, participants performed equally, or even outperformed, with the natural feedback, demonstrating that meaningful, interpretable information can be extracted from the natural feedback across versatile task demands

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Lucy Dowdall @lucydowdall.bsky.social · 19/06/2025

To put this natural feedback to the test, we created 2 new Third Thumb systems - one integrated artificial skin stretch feedback, the other integrated artificial vibrotactile feedback. We then compared the artificial to the 'natural' feedback across perceptual discrimination tasks

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Lucy Dowdall @lucydowdall.bsky.social · 19/06/2025

This is possible through the previously neglected role of the ‘natural’ feedback received as a natural by-product of how artificial limbs interface with the biological body. For example, the Third Thumb is worn and moves on the hand, this naturally generates sensory information felt across the palm

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Lucy Dowdall @lucydowdall.bsky.social · 19/06/2025

However, despite having no artificial feedback, we have previously demonstrated that people can perform a coordination task with the Third Thumb when blindfolded, relying on a sense of proprioceptive awareness of the robotic digit

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Lucy Dowdall @lucydowdall.bsky.social · 19/06/2025

Somatosensory feedback is crucial for motor learning, yet artificial limbs are thought to lack such feedback. Research has therefore focused on creating artificial sensory feedback, but these signals do not replicate the rich, multimodal information available from natural touch-see shorturl.at/2PMyU

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Lucy Dowdall @lucydowdall.bsky.social · 19/06/2025

Excited to share our new interdisciplinary work exploring the sensory representation of an artificial body part, combing datasets and methodologies to explore sensorimotor integration of the Third Thumb, a 2 DoF hand augmentation device (@daniclode.bsky.social) doi.org/10.1101/2025.06.16.658246

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