Losing the sense of touch can significantly impact daily life. Individuals with spinal cord injuries might no longer feel their hands, even though they are still there. Without tactile feedback, simple activities like holding a cup, buttoning a shirt, or handling delicate objects become much more challenging because the brain no longer receives signals about pressure or contact.
Researchers have dedicated years to finding ways to restore this vital sense. Recent studies indicate that one promising technology may be safe for long-term use. Dr. Michael Smith and colleagues from the University of Pittsburgh and the University of Chicago have shared positive results from over a decade of research on a specialized brain-computer interface.
Their findings, published in Science Translational Medicine, focus on intracortical microstimulation—tiny electrical pulses delivered directly into the brain regions responsible for touch. Brain-computer interfaces (BCIs) are devices that create a direct link between the brain and external machinery, drawing global attention for their potential to help individuals who have lost movement, speech, hearing, or vision.
Some BCIs enable paralysis patients to control computers or robotic limbs purely via thought, while others aim to restore sensory perceptions by precisely stimulating brain areas. A major concern has always been safety—how well electrodes stay functional over years, whether stimulation causes adverse effects, and if the brain continues to respond normally over time.
To explore these questions, the team studied five individuals living with spinal injuries. Over a combined total of 27 years, these participants received approximately 168 million electrical pulses through implanted electrodes. According to the researchers, this represents the longest human safety study of intracortical microstimulation to date.
This research builds on earlier breakthroughs. In 2012, the Pittsburgh team enabled a paralyzed person to operate a robotic arm using implanted brain signals. Later, they added artificial touch via sensory cortex stimulation, allowing participants to feel sensations while manipulating the robotic limb. The University of Chicago expanded on this work with their own participants.
The new findings reveal that the stimulation remained highly stable over time. When electrical pulses were delivered to the part of the brain representing the hand, participants uniformly experienced sensations in their hands, rather than other body parts. These sensations remained consistently localized even after many years.
The study also looked for adverse effects. Persistent sensations after stimulation were exceedingly rare, occurring only approximately once every 23,000 sessions. Most sensations faded within seconds, did not cause pain, and did not require medical intervention. While some electrodes gradually became less sensitive, many continued functioning for years. Even after ten years, one participant still had about 60% of the electrodes active.
These results suggest that long-term brain stimulation could become a viable option for future medical devices beyond research settings. Such systems might eventually allow people with paralysis to control assistive devices and experience touch naturally. Additionally, the safety evidence could accelerate similar approaches for restoring hearing and vision by stimulating other parts of the brain—a crucial step toward wider application.
Although these findings are promising, further research is essential. The study involved only five participants, so larger trials are necessary to confirm the safety and efficacy of long-term intracortical stimulation. Researchers continue to work on making the artificial touch feel more natural, simplifying device configurations, and enhancing durability over time.
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Source: University of Pittsburgh.