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Neurostimulation restores feeling in paralysed hand for months after

Keith Thomas, who has paralysis, but can now move and feel his hands again thanks to a brain implant
Keith Thomas has paralysis, but can now move and feel his hands again thanks to a brain implant
MATTHEW LIBASSI/Feinstein Institutes for Medical research

A man who became paralysed after a diving accident six years ago regained the ability to move and feel pressure in his hands thanks to brain stimulation. Now, researchers have revealed he maintained this ability for months after the stimulation was turned off. This suggests the intervention has caused a rerouting of his neuronal connections through neuroplasticity.

“We turned everything off completely, for many months, and yet he’s maintained these gains,” says Chad Bouton at the Feinstein Institutes for Medical Research in New York. “That’s unheard of.”

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Keith Thomas, 48, was paralysed from the chest down in July 2020. He had no sensation or control over his limbs and had significant muscle wasting, says Bouton.

In 2023, Bouton and his colleagues performed a double neural bypass surgery on Thomas, placing five electrodes into his brain in regions associated with arm movements and feeling. They then connected computer cables to these electrodes, so artificial intelligence could interpret his movement intentions. That information was then wired into electronic splints that stimulated his arms, hands and fingers to carry out his intended movements, enabling him to pick up coffee cups and scratch his face.

To recreate the sense of feeling, the team embedded force sensors into 3D-printed wearable devices for Thomas’s hands and fingers, which sent feedback via electrical stimulation into the brain’s sensory areas.

After conducting a series of experiments – which even involved Thomas feeling objects through another person’s hand – Bouton says the team planned to stop the stimulation for about a month, to test for any lingering effects. “Then we had a fire in the building, and it actually forced us to stop stimulation for even longer than we’d planned, for about three months.”

Thomas has even been able to move and feel sensations through another person’s hand
MATTHEW LIBASSI/Feinstein Institutes for Medical research

The unexpected interruption led to surprising findings: Thomas continued to maintain strength, feeling and function in his hands. “He’s now also controlling individual fingers with even more accuracy, so that’s big,” says Bouton.

In a video interview with New Scientist, Thomas raised his elbows nearly to shoulder level and described feeling “tingling” in his wrist in response to pressure, even when he’s “unplugged from the computer”. “When I first felt it, it was amazing,” he says. “I’m used to it now.”

Sergey Stavisky at the University of California, Davis, says the work suggests that this approach promotes lasting recovery of the nervous system. “The goal is to help the nervous system partially heal so the person can move their own body better,” he says.

“If these improvements persist even when the system is turned off, then the device is doing more than temporarily restoring function,” says Daniel Lu at the University of California, Los Angeles. “It may be helping the nervous system reorganise itself through neuroplasticity.”

This describes the brain’s ability to rewire itself by forming new neural connections, such as after an injury or even in response to a new hobby. “After an injury such as spinal cord injury, those same mechanisms may help restore function by strengthening spared pathways or recruiting alternative circuits, allowing neural signals to travel through networks that were previously too weak to support meaningful movement,” says Lu.

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The researchers have observed stronger neural responses in Thomas’s sensory cortex since the intervention.

But this is just a single case report, so it’s unclear how well this approach would work on other people with paralysis from different types of injuries. Charles Greenspon at the University of Chicago says he has spent years working on stimulation to restore touch in people with spinal cord injuries and continues to find that some respond better than others, and some not at all. “And we have no idea why,” he says. “So, the question is: can you replicate it? This is a really ambitious study, but we need to see them replicating their results in more participants before we believe the hype.”

As to Thomas’s future, “at this point now we know nothing’s impossible, or anything’s possible”, says Boulton. “I think it’s possible he will continue to to improve,” he adds.

Journal Reference:

Nature Medicine DOI: 10.1038/s41591-026-04498-0

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Game that reduces dementia risk may clear amyloid from men’s brains

Beta-amyloid forms plaques in the brain (seen in yellow) that play a role in Alzheimer’s disease
JUAN GAERTNER/SCIENCE PHOTO LIBRARY/Alamy

A cognitive “speed training” game that cuts dementia risk by 25 per cent alters levels of beta-amyloid, a protein that clogs up the brain in Alzheimer’s disease, in men, but not in women.

It is the first time brain training has been shown to influence the levels of a neurodegenerative marker, strengthening the evidence suggesting that mental exercises can boost brain health.

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“One of the main markers that’s indicative of future dementia risk got better for men who completed cognitive speed training,” says Hye Won Chai at Clemson University in South Carolina, who presented the research at the Alzheimer’s Association International Conference in London on 12 July.

The computer-based speed training involves recalling where objects have flashed up, with the task becoming harder as performance improves. A prior 20-year study by some of Chai’s colleagues showed that people aged 65 and older, who did the training were 25 per cent less likely to be diagnosed with Alzheimer’s disease or a related form of dementia compared with a control group.

In the latest study, Chai and her team recruited a separate group of 53 people from the US aged 65 and older, 13 of whom were male. About a third of the participants were asked to complete between 2 and 4 hours of speed training each week for 4.5 months.

The remaining participants were either told to spend the same amount of time playing games such as Solitaire, word search and a game similar to Connect 4, or to complete another kind of brain training in which they had to strategically track objects and switch between tasks.

To explore how speed training may reduce dementia risk, the team collected blood samples from all of the participants at the start and end of the training period.

This revealed that, among men, speed training increased the ratio of two forms of beta-amyloid found in the blood, which suggests the training boosted the brain’s ability to clear beta-amyloid 42. This protein forms clumps called plaques in the brain during Alzheimer’s disease, disrupting brain function. The other two kinds of training had no effect.

“It’s a really cool finding,” says Sasha Novozhilova at McGill University in Montreal. “It is definitely strengthening what they’ve [previously] shown with the reduction in dementia.”

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Some Alzheimer’s treatments, such as lecanemab, have been designed to help clear amyloid from the brain, but they only marginally slow cognitive decline during Alzheimer’s disease. The limited benefit seen in trials is probably down to these treatments being taken at a relatively late stage of the condition, when substantial brain damage has already occurred, says Andrea Castegnaro at University College London.

Engaging in cognitive training to reduce beta-amyloid build-up before dementia develops may have a bigger effect on dementia because it would be done before much brain damage has occurred, says Castegnaro.

However, cognitive training had no effect on amyloid levels in female participants in the study. This suggests that speed training reduces dementia risk in different ways in women and men, says Chai.

The team hopes to explore how speed training may benefit women in future studies, says Chai. But first, the findings need to be verified in geographically and ethnically diverse groups, says Novozhilova.