Why prosthetics don’t have to look like the real thing

Iphoto shoot British model and disability rights activist Kelly Knox poses with a one-of-a-kind prosthetic leg. Mr. Knox was born with his left arm missing from the elbow. From the ends of her arms, she has dozens of vertebrae-like structures extending out, forming long, winding tentacles.

The limbs are certainly impressive. It’s also dexterous. Mr. Knox can control his movements through pressure sensors in his shoes that are wirelessly connected to his limbs. The artificial tendon can be tightened or loosened, allowing the tentacles to reach and grab. The limb, which was separated from Mr. Knox and titled “VINE 2.0,” will be exhibited at “BODIES…The Exhibition.”” It will be held later this year at the Luxor hotel and casino in Las Vegas.

The limbs were designed by artist Sophie de Oliveira Barata and designer and engineer Dani Claude. Although it is a work of art, it is inspired by recent and interesting developments in neuroscience, and the reason why prosthetic limbs need to look and behave like biological prostheses is because they are at least as sensitive to the initial neural Scientific principles suggest that it does not exist.

This development concerns a phenomenon called “embodiment” and is of interest to both neuroscientists and prosthetic limb manufacturers. Embodiment is the way the brain identifies with the body in which it is located and determines the boundaries of what is considered “self” and what is considered “other.”

In some cases, materialization may not work. According to some papers, most amputees (60% to 80% worldwide) often continue to experience the presence of the missing limb for many years after the initial amputation. there is. This “phantom limb syndrome” (please) shows that the brain’s ideas about the boundaries of the body don’t always match physical reality.

Prosthetic limb manufacturers have long wanted to use physicality to design designs that feel like extensions of the body, rather than foreign objects attached to it.Treatment pleaseThe study, which uses mirrors to create the illusion that the missing limb is still there, could persuade the brain to create a prosthetic limb if it matches the shape and function of the limb being replaced. I suggested that.

However, scientists’ understanding of embodiment is beginning to change. In a series of experiments in 2018 and 2020, neuroscientist Tamar Makin, who runs the Plasticity Laboratory at the University of Cambridge, used functional magnetic resonance imaging to record blood flow in different parts of the brain. I looked into someone’s head. – Double amputee.

It’s not what you think

Makin had them look at pictures of three different types of objects: biological hands, prosthetic hands, and hand tools such as brushes and spoons. By comparing which parts of the subjects’ brains responded, Makin was able to determine whether the brain was interpreting the prosthetic hand as something like a biological hand, or as an object more like a tool. I wanted to prove that.

To Dr. Makin’s surprise, the answer seemed to be neither. Instead, she says, her brain “puts the prosthetic limb in a category entirely of its own, clearly distinguishing it from other prosthetics.” That’s true whether the prosthetic hand is a decorative one designed to look like an organic hand, a functional one, a sophisticated robotic version or a simple hook. .

This does not mean that prosthetics cannot be realized. Many amputees report embodying their prosthetic limbs to some degree. But what it proves is that whether a prosthetic limb is embodied has little to do with whether it looks like a biological arm or leg.

This has several implications for prosthesis design. One is to embrace all kinds of innovations in materials, colors, and shapes. This is where Ms. de Oliveira Barata comes into the picture. She runs the Alternative Limb Project (A.L.P.) is a British studio that creates custom prosthetic limbs. Ms. Oliveira-Barata, who has a background in makeup and special effects, started by creating realistic limbs for amputees. But a project with a young girl who decided to cover her alternate legs with cartoons changed her perspective.

recently, A.L.P. We create impressive, high-concept prosthetics for our clients. Her first big request came from British singer Victoria Modesta, who had her below-the-knee amputation. Inspired by an idea that occurred to Ms. Modesta in her dream, Ms. de Oliveira Barata designed a black prosthetic leg made of metal in the shape of a long conical spike vaguely reminiscent of a giant stiletto heel. did. Modesta performed at the closing ceremony of the 2012 Paralympic Games using another of De Oliveira Barata’s creations, legs encased in silver and glass crystals.

And if a prosthesis does not need to mimic the limb it replaces, perhaps a prosthesis could become more than just a replacement? Ms. Claude is an expert in the design of robotic prostheses controlled by artificial tendons . She is passionate about exploring the potential to enhance the existing body with new functions and making prosthetics “a technology that benefits everyone, not just amputees.” To that end, she designed a “third thumb,” a small, strong prosthetic finger that does exactly what it says on the tin. Like Mr. Knox’s vine arm, this thumb, which is controlled by pressure sensors in the shoe, can be used to replace the missing big toe. However, it can also be added to the intact hand opposite the existing biological thumb.

Having two thumbs “opens up an incredible range of what the human hand can do,” Ms. Claude says. Many tasks involve holding and manipulating objects at the same time, such as peeling a banana or opening a bottle of soft drink with one hand. Using toe controls is primitive compared to more sophisticated prosthetic hands on the market, which are designed to be controlled by picking up signals from the wearer’s remaining muscles. It may seem that it is.

But Claude says the opposite is true. Myoelectric prostheses can be slow and cumbersome. Additionally, the muscles remaining at the amputation site are unlikely to be the same muscles used to move the missing limb, so it may take several months to learn how to use the muscles in a prosthetic leg. there is. In contrast, shoe-mounted controls are relatively quick to learn.

In the future, it may be possible to provide such prosthetics with artificial sensory feedback. In a paper published in November 2023 science robotics, a team of Chinese researchers led by Beihang University roboticist Li Wen has described a flexible robotic arm that mimics the tentacles of an octopus. Although it was not designed as a prosthetic limb, the tentacles are controlled by a finger glove that fits the wearer’s index finger and provides touch feedback through the same mechanism that controls the tentacles.

Neither Ms de Oliveira Barata nor Ms Claude are neuroscientists. But academic researchers are also becoming interested. Ms. Claude is working with Dr. Makin to study how the brain adapts to the body’s augmentation. They are particularly interested in how the brain reallocates its cognitive resources to accommodate new appendages, and whether such appendages can materialize. “I don’t think we’re even close to the limits of what’s possible yet,” says Ms. Claude. “But we’re certainly going to figure it out.” ■

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