For people living with paralysis after a spinal cord injury, losing the ability to feel their hands can be just as difficult as losing movement.
Touch allows people to judge how tightly they are holding an object, feel temperature, and safely interact with the world.
Without that feedback, daily activities become far more challenging. Scientists have long believed that replacing these missing signals might be possible, and new research shows that this idea may be closer to reality than ever before.
A team from the University of Pittsburgh and the University of Chicago has completed the longest study ever to examine the safety of delivering tiny electrical signals directly into the human brain to recreate touch sensations. Their research was published in Science Translational Medicine and followed five volunteers with spinal cord injuries over many years.
The technology relies on brain-computer interfaces, often called BCIs. These systems connect implanted electrodes with computers that can either read signals from the brain or send carefully controlled signals back into it.
In recent years, BCIs have attracted enormous interest because they may eventually help people recover movement, communicate after severe injury, or regain lost senses.
The current study focused on the sensory part of the brain, which normally receives information from the skin. Researchers implanted tiny electrodes into this region and delivered carefully controlled electrical pulses. These pulses created the feeling that the participants were touching something with their hands, even though the signals were generated artificially.
Over the course of the project, the five participants received approximately 168 million stimulation pulses. Altogether, the implants remained inside participants for a combined total of 27 years. Such an extended study allowed scientists to answer questions that shorter experiments simply could not address.
One of the most encouraging findings was that the sensations remained stable. Stimulation delivered to the hand area of the brain continued producing sensations in the hand rather than spreading unpredictably to other parts of the body. This stability is essential if future devices are to provide reliable sensory feedback during everyday activities.
Safety was another major focus. The researchers carefully monitored participants for unwanted side effects throughout the study. Lingering sensations after stimulation was turned off occurred only very rarely and almost always disappeared within a few seconds.
None were painful or required medical treatment. Although some electrodes gradually lost sensitivity over time, many remained usable for years, demonstrating impressive durability for implanted medical technology.
The project builds on more than a decade of pioneering work. Earlier studies from the University of Pittsburgh showed that people with paralysis could control robotic arms using signals from implanted brain electrodes.
Researchers later combined movement with artificial touch, making control much more natural. The latest study strengthens confidence that these approaches may one day become practical treatments rather than laboratory demonstrations.
Scientists believe the importance of this research extends beyond restoring touch. Similar brain stimulation methods are being investigated to restore vision and hearing by targeting different brain regions. Long-term safety information from this study provides valuable evidence that may help speed development of future treatments for many neurological conditions.
The researchers continue improving the technology. Their goals include creating more realistic touch sensations, reducing the amount of adjustment needed for each user, and making future systems simple enough for use at home instead of only in specialised research centres.
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Source: University of Pittsburgh.
