Neural vs. Myoelectric Prostheses: A Revolution in Bionic Limbs

Neural vs. Myoelectric Prostheses: A Revolution in Bionic Limbs

When an individual loses a hand, they also lose the intricate motor skills and sensory experiences associated with it. An ideal prosthesis should not only restore movement and control but also replicate the natural interaction between the hand and the environment. Despite advances in prosthetic technology, most commercially available prostheses are still far from replicating the functionality of a biological limb.

The Limitations of Myoelectric Prostheses

Currently, most prosthetic limbs operate using myoelectric control. This means they rely on electrical signals generated by the remaining muscles in the residual limb. However, due to the nature of forearm amputations, a significant number of muscles that control the fingers and wrist are lost. A healthy hand relies on 22 muscles to achieve its complex dexterity, but an amputated forearm retains only a fraction of these, leading to a reduced range of motion and control in myoelectric prostheses.

Myoelectric prostheses function by detecting signals from the remaining muscles, but these signals are limited in number and strength. For each movement, at least two distinct signals are needed: one to activate the prosthesis and another to return it to its original position. While the most advanced myoelectric prostheses offer up to 24 predefined movements, many users can only effectively control three or four movements due to the difficulty of commanding the prosthesis through atypical muscle contractions. This constraint makes prosthetic control challenging and unnatural for many amputees.

The Promise of Neural Prostheses

Unlike myoelectric systems, neural prostheses are designed to be controlled using motor signals from the nerves in the residual limb. These signals remain intact even after amputation because they originate in the brain and are directly related to the movement commands once sent to the lost limb. By decoding these neural signals, it is possible to reconstruct a much wider range of movements compared to myoelectric control.

The NerveRepack project aims to bring this vision to reality by leveraging neural implants to capture motor commands directly from the nerves of the residual limb. This approach allows for a more natural and intuitive control mechanism, enabling amputees to manipulate objects with greater precision and fluidity. With a direct connection to the nervous system, NerveRepack’s prosthetic technology seeks to restore lost motor functions and allow users to regain control over everyday activities in a way that closely mirrors the movement of a natural hand.

Personalized Movement Algorithms for Prosthetic Arms

One of the groundbreaking innovations of NerveRepack’s neural prosthesis is the implementation of personalized movement algorithms. Unlike traditional prostheses that provide a fixed set of motions with identical characteristics for all users, this new technology adapts finger movements to each patient’s unique neural commands.

For instance, conventional prostheses execute a predefined grasping motion when holding a spherical object. The movement speed, acceleration, and trajectory remain the same for every user, as these parameters are set by the manufacturer and cannot be adjusted. In contrast, a neural prosthesis can detect subtle variations in neural signals, allowing the patient to modify grip strength, speed, and movement patterns naturally, just as they would with a biological hand. This personalization is made possible by an advanced neural interface that captures and processes signals from the median and ulnar nerves.

Expanding the Range of Motion with Neural Control

A significant limitation of myoelectric prostheses is the small number of movements they can perform due to the limited number of distinct signals available from the residual muscles. As mentioned earlier, most myoelectric prostheses require at least two signals per movement, and patients often struggle to control more than a few movements effectively.

Neural prostheses eliminate this barrier by using the patient's original brain commands. Since neural signals contain comprehensive movement information—such as speed, direction, and force — it becomes possible to execute a broader range of motions. The NerveRepack system aims to acquire at least 31 distinct motor patterns from the neural interface, allowing patients to control a significantly larger number of movements effortlessly. This increased functionality translates into smoother transitions between movements and a more natural prosthetic experience.

Transitioning from Myoelectric to Neural Prostheses

An essential advantage of the NerveRepack system is its compatibility with existing myoelectric prosthetic designs. This allows for a gradual transition from conventional myoelectric prostheses to advanced neural prostheses without requiring a complete redesign of prosthetic limbs.

A useful analogy for understanding this transition is the shift from gasoline-powered cars to electric vehicles. Car manufacturers did not entirely redesign automobiles; instead, they replaced internal combustion engines with electric motors while maintaining the same body, chassis, and controls. Similarly, neural prostheses can be integrated into existing myoelectric prosthetic structures, upgrading their functionality without requiring users to adapt to an entirely new device.

By enhancing current prostheses with neural interfaces, amputees can benefit from significantly improved control and usability. This advancement will enable them to perform more complex movements naturally, reducing the cognitive effort required to operate a prosthetic limb and improving overall quality of life.

The Future of Neural Prostheses

The ultimate goal of the NerveRepack project is to make neural prostheses widely available to millions of amputees worldwide. By refining neural interface technology and making it more accessible, NerveRepack aims to transform the prosthetic industry and provide amputees with an unprecedented level of control and independence.

In the coming years, advancements in neural implants, signal processing algorithms, and prosthetic design will continue to improve the functionality and usability of neural prostheses. As these technologies evolve, they will bring us closer to a future where artificial limbs function almost as seamlessly as their biological counterparts.

NerveRepack’s innovations in neural prosthetic technology mark a significant advancement in the field of bionics, enabling a more natural connection between the user’s nervous system and the prosthetic limb. By utilizing neural signals as a source of control, this new approach opens the door to prosthetic systems that more accurately reflect the user’s intended movements. As a result, individuals with limb loss may regain refined motor abilities and interact with their environment in a way that feels more intuitive and responsive.