Summary: Experts are making strides in mental excitement to bring back feel sensations in prosthetic limbs. By using electrodes in the body’s feel center, they can generate firm, precise sensations, yet allowing users to feel the shape and motion of objects.
This development might help robotic people accomplish tasks that require fine engine power with confidence. Long-term assessments show regular sensation locations, essential for real-world usability.
Advanced activation patterns, which mimic natural touch, further enhance the sensory experience. These developments represent important advancements in neuroprosthetics that enhance quality of life for those who have limb loss or visual deficits.
Important Facts:
- Secure Sensations: Mental stimulation effectively evoked the same feel sensations over years, enhancing usability.
- Users could understand movement and shapes, such as sliding objects or letters, using active contact patterns of excitement.
- Large Software: The technique could expand to restoring other types of visual damage, including post-mastectomy effect.
Origin: University of Chicago
Without looking at them, you can possibly accomplish an incredible number of things. Many of those straightforward tasks become unpleasant, however, if you put on boots that aggravate your sense of touch.
If you lose proprioception, which measures your body’s perception of its relative position and action, you could end up breaking something or hurting yourself.
” Most people don’t realize how frequently they rely on feel instead of vision — reading, walking, picking up a thin cup of water”, said Charles Greenspon, PhD, a researcher at the University of Chicago.
” If you can’t experience, you have to continually watch your hands while doing something, and you still risk spilling, crushing or dropping things”.
Greenspon and his research collaborators recently published papers in , Nature Biomedical Engineering , and , Science , documenting major progress on a technology designed to address exactly this problem: clear, carefully timed electrical stimulation of the brain that can imitate sensory feedback to provide complex “feeling” to bionic hands.
The science of restoring sensation
These new studies build on years of collaboration among scientists and engineers at UChicago, the University of Pittsburgh, Northwestern University, Case Western Reserve University and Blackrock Neurotech.
Together, they are developing, creating, implementing, and improving brain-computer interfaces (BCIs ) and robotic prosthetic arms that are intended to restore motor control and sensation in people who have lost significant limb function.
On the UChicago side, the research was led by neuroscientist , Sliman Bensmaia, PhD, until his unexpected passing in 2023.
The researchers place tiny electrode arrays in the areas of the brain responsible for moving and feeling the hand in an attempt to mimic prosthetic sensation.
A robotic arm can be moved by a participant by simply thinking about moving it, and sensors on that robotic limb can produce intracortical microstimulation ( ICMS ) pulses in the area of the brain dedicated to touch.
According to Greenspon, this touch center stimulation for about ten years could only give the user a quick sense of contact in various areas of the hand.
We could “elicit the feeling that you were touching something,” he said, but it was mostly just an on/off signal and frequently it was difficult to determine the source of the hand contact.
Important milestones have been reached in the recently released results.
improving our understanding of artificial touch
In the , first study, published in , Nature Biomedical Engineering, Greenspon and his colleagues focused on ensuring that electrically evoked touch sensations are stable, accurately localized and strong enough to be useful for everyday tasks.
The researchers created detailed “maps” of brain areas that were related to particular parts of the hand by giving short pulses to individual electrodes in participants ‘ touch centers and having them rate where and how strongly they felt each sensation.
The results of the testing showed that participants experience a stronger, clearer touch when two closely spaced electrodes are stimulated together, which can improve their ability to identify and assess the correct pressure in the hand.
The researchers also ran thorough examinations to verify that the same electrode consistently produces a sensation related to a particular location.
According to Greenspon, who was the lead author on this paper,” If I stimulate an electrode on day one and a participant feels it on their thumb,” we can test that same electrode on days 100, 1, 000, or even many years later, and they still feel it in roughly the same spot.”
Any clinical device would need to be stable enough for a patient to rely on it in daily life, in terms of practicality. An electrode would be frustrating and require frequent recalibration if it constantly shifts its” touch location” or produces inconsistent sensations.
By contrast, the long-term consistency that this study discovered could help prosthetic users gain the same level of confidence as they would in their natural limbs in terms of motor control and touch control.
adding movements and shapes
The , complementary , Science , paper , went a step further to make artificial touch even more immersive and intuitive. Giacomo Valle, PhD, a former postdoctoral fellow at UChicago and a former postdoctoral fellow at Chalmers University of Technology in Sweden, was the first author to lead the project.
” Two electrodes next to each other in the brain don’t create sensations that’ tile’ the hand in neat little patches with one-to-one correspondence, instead, the sensory locations overlap”, explained Greenspon, who shared senior authorship of this paper with Bensmaia.
The researchers looked into whether they could use this overlapping nature to create sensations that could allow users to feel the motion of an object or the movement of something sliding along their skin.
The scientists created sensations that travelled across the sensory map by activating them in carefully orchestrated patterns after finding pairs or clusters of electrodes whose” touch zones” overlapped.
Despite the fact that the stimulus was delivered in small, discrete steps, participants reported feeling a light gliding touch glide smoothly over their fingers.
The scientists believe that this result comes from the brain’s remarkable ability to combine sensory inputs and interpret them as coherent, moving experiences by “filling in” perceived gaps.
Participants ‘ ability to distinguish complex tactile shapes and react to changes in the objects they touched was also significantly improved by the sequential activation method.
They could occasionally recognize letters from the alphabet that had been electrically” traced” on their fingertips, and they could hold a steering wheel in place when it started to slack off.
These advancements help to bring bionic feedback closer to the precise, complex, adaptive abilities of natural touch, opening the door for prosthetics that make it possible to handle simple objects and respond to shifting stimuli with confidence.
The future of neuroprosthetics
The researchers anticipate that as electrode designs and surgical techniques become more advanced, the hand’s coverage will increase, giving more lifelike feedback.
Robert Gaunt, PhD, associate professor of physical medicine and rehabilitation and lead of the stimulation work at the University of Pittsburgh, said,” We hope to incorporate the results of these two studies into our robotics systems, where we have already , shown , that even simple stimulation strategies can improve people’s abilities to control robotic arms with their brains.
Greenspon emphasized that the goal of this work is to improve the quality of life and limb loss for people who have paralysis.
This research is for the people in our lives who get injured and lose the use of a limb, he said.” We all care about the people in our lives who get injured and lose the use of a limb,” he said.
” This is how we restore touch to people. It’s the forefront of restorative neurotechnology, and we’re working to expand the approach to other regions of the brain”.
The approach also has potential for those who have sensory loss of a different kind. In fact, the group has collaborated with UChicago’s surgeons and obstetricians on the Bionic Breast Project, an implantable device that can restore the sensation of touch after mastectomy.
These most recent studies provide proof that the path to restoring touch is getting simpler, despite the difficulties that still exist. Researchers become more optimistic about a future where a prosthetic body part is not just a functional tool but also a way to experience the world with each new set of findings.
About this research in neurotechnology and neuroprosthetics
Author: Grace Niewijk
Source: University of Chicago
Contact: Grace Niewijk – University of Chicago
Image: The image is credited to Chalmers University of Technology | Boid | David Ljungberg
Original Research: Closed access.
Giacomo Valle et al.,” Tactile edges and motion are induced by human somatosensory cortex pattern microstimulation..” Science
Open access.
Giacomo Valle and colleagues ‘ work” Evoking stable and precise tactile sensations via somatosensory cortex multi-electrode intracortical microstimulation.” Nature Biomedical Engineering
Abstract
Tactile edges and motion are induced by human somatosensory cortex pattern microstimulation.
Sensory cortex evokes tactile sensations that can be systematically altered by varying stimulation parameters through intracortical microstimulation ( ICMS ). However, ICMS currently provides an imperfect sense of touch, limiting manual dexterity and tactile experience.
We sought to inform people with paralysis about local geometry and apparent motion of objects on their skin by using our understanding of how tactile features are encoded in the primary somatosensory cortex ( S1 ).
We also delivered ICMS through electrodes that had spatially patterned projected fields ( PFs ), causing edges-feeling sensations. Then, we created complex PFs that can be used to encode arbitrary skin indentation patterns and tactile patterns.
We elicited motion across the skin by delivering ICMS with a spatiotemporally patterned pattern, which could be controlled in terms of speed and direction. Thus, we improved individuals ‘ tactile experience and use of brain-controlled bionic hands.
Abstract
Evoking stable and precise tactile sensations via somatosensory cortex multi-electrode intracortical microstimulation
Intracortical microstimulation ( ICMS ) of the primary somatosensory cortex can partially restore tactile feedback from brain-controlled bionic hands.
In ICMS, the electrode’s location determines where the percepts are located, and the percept intensity determines the stimulation frequency and amplitude. The contact force of each sensor can be used to determine the stimulus’s amplitude because sensors on a bionic hand can be connected to somatotopically appropriate electrodes.
We present a thorough analysis of the intensity and localization of ICMS-evoked percepts in three cases of cervical spinal cord injury.
A retrospective analysis of projected fields revealed that they were typically set up as a focal hotspot with diffuse borders, arranged somatotopically in accordance with their underlying receptive fields, and stable throughout the study.
Individual electrodes typically evoked only weak sensations when testing whether a group could quickly localize a single ICMS presentation, making object localization and discrimination challenging.
However, overlapping projected fields from multiple electrodes resulted in more localizable and intense sensations and made it possible to use a bionic hand with greater precision.
