New innovation paves the way for natural feeling bionic limbs

The complexity of human movement stems from the central nervous system's ability to organize motion using modular control structures. These structures, known as synergies, allow for the coordinated activation of multiple muscles, simplifying the control of intricate motor tasks.

This principle extends to spinal motoneurons, the nerve cells responsible for stimulating muscle contractions. Researchers have now demonstrated that these neural synergies align with postural synergies, the patterns of joint coordination that define hand movements.

For individuals using prosthetic limbs, this discovery has profound implications. Current prosthetic hands often feel unnatural because they fail to integrate with the body's existing neural control mechanisms. Many users abandon them due to their limited dexterity and awkward operation.

Scientists have now applied the concept of neuromuscular synergies to develop a prosthetic hand that mirrors the natural coordination of a human hand. This innovation enhances precision and fluidity, bridging the gap between biological and artificial movement.

Motor control relies on the ability to coordinate multiple muscle groups simultaneously. The brain and spinal cord manage this complexity by using synergy-based control, a strategy that reduces the number of signals needed to execute movements.

The human hand, for instance, can achieve a wide range of postures by combining a few fundamental motion patterns rather than independently controlling each finger.

Recent research has shown that motoneurons, which relay signals from the spinal cord to muscles, are organized in a way that reflects these movement patterns. Instead of treating individual muscles as the basic units of movement, this new perspective considers groups of motoneurons as functional units.

By analyzing the electrical activity of motoneurons, researchers have identified neural synergies that correspond to natural grasping behaviors.

This insight allows prosthetic devices to be designed in a way that aligns with the body’s existing control strategies. Instead of requiring users to learn a set of unnatural commands, these advanced prostheses can be controlled using signals that naturally occur within the nervous system.

Building on these findings, researchers have developed a prosthetic hand that utilizes two primary postural synergies. This design enables the hand to perform a wide range of grasps with only two control signals. The device has 15 degrees of freedom—allowing for nearly full hand mobility—but requires only two degrees of actuation, simplifying the control process.

Unlike traditional prosthetic hands, which rely on rigid mechanisms and predefined grip patterns, this new design incorporates soft robotics principles. The hand adapts to objects, ensuring a more fluid and natural interaction with the environment. By integrating neural and postural synergies, the prosthesis allows users to control their artificial limb as seamlessly as they would a biological hand.

A key advancement in this work is the ability to decode neural signals in real time. By applying sophisticated algorithms to electromyography (EMG) data—electrical signals generated by muscle activity—scientists can identify motoneuron synergies and translate them into movement. This process enables intuitive control, making the prosthetic hand feel like an extension of the user’s body.

The prosthetic hand was tested with 11 able-bodied participants and three individuals with limb loss. The results confirmed that integrating motoneuron decoding with synergy-based control enhances dexterity and ease of use. Users could grasp and manipulate various objects naturally, demonstrating a level of fluidity not previously achievable in prosthetic technology.

This research, published in Science Robotics, led by teams at the Istituto Italiano di Tecnologia in Italy and Imperial College London in the UK, represents a major leap forward in bionics. Funded by the European Research Council under the “Natural BionicS” project, the study aims to develop prosthetic limbs that feel and function as naturally as biological ones.

The findings could have applications beyond prosthetics. By creating seamless connections between the nervous system and robotic components, researchers open the door to advanced human-machine integration. This technology could eventually be used to develop exoskeletons, robotic augmentation devices, and even neural interfaces for controlling external systems.

For prosthetic users, the impact is immediate. This synergy-driven approach offers greater autonomy, restoring not just movement but also a sense of natural interaction with the world.

By bridging the gap between neural control and artificial limbs, this research brings us closer to a future where bionic technology feels as natural as the human body itself.

Note: Materials provided above by The Brighter Side of News. Content may be edited for style and length.

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