Brain stimulation that restores a sense of touch stayed safe and effective for up to ten years

What happened

Intracortical microstimulation of the somatosensory cortex can restore a sense of touch to people with spinal cord injury. This early feasibility trial followed five participants, each implanted with two Blackrock NeuroPort microelectrode arrays in the hand area of the cortex, for between 2 and 10 years.

More than 168 million stimulation pulses were delivered over a combined 27 years of implant time, without serious adverse events or direct damage to electrode health. Stimulation consistently evoked sensations localised to the hand. The current needed for a detectable sensation rose slowly, by about 3.5 microamperes per year. On average 64% (±13%) of electrodes still reliably evoked touch, a decrease of about 21% in functional electrodes; in one participant 60% still worked after 10 years. The quality and location of the sensations stayed consistent. On rare occasions (3 to 25 events across participants) a sensation lingered briefly after stimulation stopped.

Why it matters

Devices that write information into the brain, to restore touch, hearing or vision, must work for many years, and long-term human data on cortical stimulation have been scarce. This is the kind of evidence that developers and regulators need before such devices can move beyond research.

Caveats

Only five people took part, with implant durations ranging from 2 to 10 years, so the 10-year result rests on one participant. Detection thresholds did rise and about a fifth of electrodes stopped evoking sensations. The study used one type of research array. This entry is based on the abstract.