Study: Brain stimulation restores touch safely over years

PITTSBURGH – What if people who have lost the ability to feel their hands could get that sense back — not through a prosthetic glove, but through tiny pulses of electricity delivered directly to the brain?

A decade of work by scientists at the University of Pittsburgh and the University of Chicago, published today in Science Translational Medicine, shows that this approach is not only possible but safe over the long haul. Across five volunteers with spinal cord injuries, the team delivered 168 million pulses of brain stimulation via implanted brain-computer interface device over a combined 27 years of implant time without any serious adverse events — making this the first study of its kind and the longest-running study of the safety of intracortical microstimulation in humans to date.

“This research plants a flag in the ground for the safety and utility of using brain-computer interfaces to deliver sensory stimulation in clinical settings and, eventually, in people’s homes,” said senior author Robert Gaunt, Ph.D., associate professor of physical medicine and rehabilitation and a member of Pitt's Rehab Neural Engineering Labs. “For brain-computer interfaces to have real impact on people’s lives, they need to keep working safely and reliably for years. This study shows that microstimulation in the brain can do exactly that.”

Brain-computer interfaces, or BCIs, have captured public imagination in recent years, fueled by companies racing to translate the technology into products that could help people move, feel or communicate again. But the fundamental question remains: Do these systems hold up over years of daily use, and are they safe?

Pitt's Rehab Neural Engineering Labs, working with colleagues at the University of Chicago, have been at the frontier of BCI science since the early 2010s. In 2012, the Pitt investigator-led team was among the first in the world to implant electrodes in the motor cortex to let a paralyzed person control a robotic arm and later, in 2015, pioneered the approach of stimulating the sensory cortex to pair movement with a sense of touch. The University of Chicago then implanted their first participant with electrodes in sensory and motor cortex in 2020.

The new publication, made possible by five pioneer volunteers who committed years of their lives to the research, answers the field's most pressing long-term questions. Is stimulation safe? Do stimulation-evoked sensations drift to other parts of the body or fade over time? Are there unintended side effects? The team's answer, in short: stimulation stayed safe, stable and localized — even after 10 years in one participant.

Working with those volunteers, the team found that electrical pulses delivered to the hand region of the somatosensory cortex evoked sensations that stayed mapped to the hand and did not shift to other body parts over time.

Those sensations rarely lingered after stimulation was switched off — on average, only one such “persistent sensation” occurred per roughly 23,000 stimulation trials, and the vast majority lasted less than 10 seconds. None were painful and none required medical intervention.

Finally, the electrodes became less sensitive over time: 64% remained functional on average — including 60% of one participant's electrodes after a full decade in the brain, though electrodes demonstrated accelerated decay later on in the study.

“This shows that this technology doesn’t just have to be a short-term solution we test in the lab; industry can start developing long term take-home solutions for patients,” said lead author Charles Greenspon, Ph.D., an assistant professor in the Department of Neurological Surgery at the University of Chicago.

The implications stretch beyond touch. Because the same kind of microstimulation is being tested in other brain regions that process vision or hearing, the safety data reported in this paper lays the groundwork for clinical-grade neuromodulation devices that could one day help restore lost senses more broadly.

The University of Pittsburgh and University of Chicago collaboration is ongoing. The teams continue to improve the abilities of microstimulation, including how to make the sensations feel more natural, how to better control the device when stimulation is turned on and how to simplify calibrating the many parameters that control sensations.

This research was supported by the National Institute of Neurological Disorders and Stroke, the NIH BRAIN Initiative, the National Eye Institute, and the National Institute on Drug Abuse of the National Institutes of Health (grants UH3 NS107714, R35 NS122333, U01 NS108922, U01 NS123125, R01 NS130302, R01 NS131953) and the Defense Advanced Research Projects Agency (contracts N66001-16-C-4051 and N66001-10-C-4056). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health or DARPA.

Additional authors on the paper are Taylor Hobbs, Robin Lienkämper, Ph.D., Joel Ye, Tyler Simpson, M.S., Jeffrey Weiss, M.S., David Weir, M.S., Debbie Harrington, C.C.R.P., Jorge Gonzalez-Martinez, M.D., Ph.D., Michael Boninger, M.D., and Jennifer Collinger, Ph.D., all of Pitt; Ali H. Alamri, Natalya Shelchkova, Ph.D., Ashley Van Driesche, David Satzer, M.D., Giacomo Valle, Ph.D., Nicholas Hatsopoulos, Ph.D., Peter Warnke, M.D., John Downey, Ph.D., of the University of Chicago; Ceci Verbaarschot, Ph.D., of University of Texas-Southwestern; and Lee Miller, Ph.D., of Northwestern University.

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