Losing the sense of touch can dramatically change everyday life. People with spinal cord injuries may no longer feel their hands even though their hands are still there.
Without touch, simple tasks such as holding a cup, buttoning a shirt, or picking up fragile objects become much harder because the brain no longer receives information about pressure or contact.
Scientists have spent many years searching for ways to restore this missing sense, and a new study suggests that one promising technology may be safe for long-term use.
Researchers from the University of Pittsburgh and the University of Chicago have reported encouraging results after studying a special type of brain-computer interface for more than a decade.
Their findings were published in Science Translational Medicine. The study focused on a method called intracortical microstimulation, which uses tiny electrical pulses delivered directly to the part of the brain that normally processes touch.
Brain-computer interfaces are devices that create a direct connection between the brain and electronic equipment. They have attracted worldwide attention because they may one day help people who have lost movement, speech, hearing, or vision.
Some systems allow people with paralysis to control computers or robotic arms using only their thoughts. Others aim to restore lost senses by sending carefully controlled electrical signals into the brain.
One of the biggest questions has always been safety. A technology that works for a few weeks in a laboratory is very different from one that can remain inside the human body for many years. Doctors need to know whether implanted electrodes remain reliable, whether stimulation causes unwanted side effects, and whether the brain continues responding normally over time.
To answer these questions, the research team studied five volunteers living with spinal cord injuries.
Together, the participants received about 168 million electrical stimulation pulses through implanted electrodes over a combined total of 27 years with the devices in place. According to the researchers, this is the longest human safety study of intracortical microstimulation ever performed.
The work builds on years of earlier discoveries. In 2012, the University of Pittsburgh team became one of the first groups to help a person with paralysis control a robotic arm using implanted brain electrodes.
A few years later they added artificial touch by stimulating the sensory cortex, allowing participants to feel sensations while using the robotic arm. Researchers at the University of Chicago later expanded this work with their own participants.
The new study found that stimulation remained remarkably stable. When researchers delivered electrical pulses to the brain area representing the hand, participants consistently felt sensations in their hands instead of other body parts. The location of these sensations stayed stable even after many years.
The researchers also looked for possible problems. Persistent sensations after stimulation ended were extremely rare, occurring only about once in every 23,000 stimulation sessions. Most disappeared within seconds, none caused pain, and none required medical treatment.
Although some electrodes gradually became less sensitive with time, many continued functioning for years. Even after ten years, one participant still had about 60 percent of implanted electrodes working.
These findings suggest that long-term brain stimulation may be practical for future medical devices used outside research laboratories. Scientists hope future systems could eventually allow people with paralysis to both control robotic or assisted devices and naturally feel what they are touching.
The researchers also believe these safety findings could help many other fields. Similar technology is being explored to restore hearing and vision by stimulating different parts of the brain. Demonstrating long-term safety is an important step before these treatments can become more widely available.
Even with these encouraging results, additional research is still needed. The study involved only five volunteers, so larger studies will be needed to confirm the findings. Researchers also continue working to make artificial touch feel more natural, simplify device settings, and improve long-term performance.
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Source: University of Pittsburgh.
