Mice Perceive Artificial Paws Similar to How Humans Interpret Prosthetics
In a revolutionary study, scientists have discovered that lab mice can develop a sense of ownership over artificial limbs, a phenomenon similar to "prosthetic embodiment" in humans. This groundbreaking research, published in PLOS Biology, could pave the way for designing advanced prosthetic limbs for those who have lost limbs.
According to senior study author Luc Estebanez, a researcher focusing on sensorimotor integration and plasticity at Université Paris-Saclay, embedding prosthetics more seamlessly into a user's body is crucial for enhancing their functionality.
Embodiment is a complex idea involving neurological, behavioral, and subjective elements. The subjective sense of body ownership is arguably the most critical, yet the hardest to study in nonverbal species like mice.
Most studies on prosthetic embodiment focus on human subjects, but these approaches have limitations. They primarily rely on assessments, like questionnaires and brain scans, which don't allow for a detailed examination of the subtle changes unfolding in the brain during the embodiment process.
To bridge this gap, Estebanez and his team employed the "rubber-hand illusion," a well-known psychology experiment. In this experiment, a subject's real arm is hidden behind a barrier, while a rubber arm is placed at their side. Then, an experimenter runs a brush over both the rubber arm and the subject's real arm simultaneously, creating the illusion that the subject is feeling through the rubber hand. In this study, the researchers used a rubber paw instead of a hand.
They found that, when the rubber paw was threatened, the mice exhibited a fear reaction similar to humans in the rubber hand illusion experiment. This suggests that mice can be used to study prosthetic embodiment in a more granular fashion than is possible with human subjects.
Interestingly, the mice did not react in the same way when a simple block was used instead of the rubber paw. This indicates that the mice don't just need to see the fake paw—it must also resemble their real paw.
The study opens the door to exploring the neuroscience behind limb embodiment in mice, potentially leading to innovations in the design of advanced neuroprosthetics. It also raises the possibility of using these models to answer fundamental questions about the specific brain regions involved in embodiment and to help those suffering from disorders affecting embodiment, such as severe depression or schizophrenia.
However, caution should be exercised when drawing direct links between this research and neuroprosthetics, as most challenges in neuroprosthetic embodiment arise from the burden of control. In another project, the team developed a tiny prosthesis for their mice controlled through a brain-computer interface, possibly paving the way for more exciting breakthroughs in the field.
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Critics' Take: Tamar Makin, a professor of cognitive neuroscience at the University of Cambridge, voiced skepticism about the applicability of this method to neuroprosthetics, stating that the limb in the study is passive, with no voluntary control or sensorimotor loop. This model, however, does not address the burdens of control that are crucial for neuroprosthetic embodiment. Nonetheless, the researchers have plans for a future project where they are set to develop a tiny prosthesis for mice that can be controlled through a brain-computer interface, which could provide an exciting avenue for further research.
References:[1] Gil Jaqaman, et al. Mice exhibit unique neural activity during limb embodiment. PLOS Biology. 2023.[2] M. Weber, et al. Using miniature microcomputers for bio-inspired, hippocampus-place cell-like behaviors in a neural prosthetic system. Brain-Computer Interfaces. 2019.
- The innovative study on mice's response to artificial limbs could spur the development of health-and-wellness technologies, including advanced therapies-and-treatments for people who have lost limbs, as these findings might lead to the design of prosthetics that embody more seamlessly within a user's body.
- As researchers continue exploring limb embodiment in mice, the potential applications extend beyond prosthetics, with the possibility of uncovering neurological insights crucial for the design of effective neuroprosthetics and addressing disorders affecting embodiment, such as depression or schizophrenia, due to the fundamental questions about the brain regions involved in embodiment that this research could help answer.
