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Amateur Scientist Tries to Hack Human-Human Interface to Treat His Own Spinal Cord Injury

Amateur scientist Gianni Garulli in his lab, trying to hack Human-Human Interface to treat his spinal cord injury

We’ve been doing it for 10 years already: connecting two humans so that one uses their own brain signals to control the other one’s limb. But how about hooking up two limbs of a single human so that one limb can control the other?

This is exactly what Gianni Garulli, a hardware and firmware developer from Lonato del Garda, Italy, tried to do. Having suffered a spinal cord injury that affected his legs, one more heavily than the other, he was on the lookout for treatment, even if it required some serious tinkering.

So when his daughter Elisa came across our booth at the FENS 2022 in Paris, one thing caught her eye: the Human-Human Interface (HHI) and the idea of neuroplasticity. Christmas was nearing and with it, their old tradition of spending holiday time doing projects together. As it happened, the perfect Christmas gift was there for the taking.

Elisa’s own background helped too. As a PhD student at Charité University Hospital, Berlin, she studies neurotechnology and holds an MSc in biotech. Moreover, she used to be part of O.W.L. (Open Wet Lab), a biohacking association committed to bringing science out of labs and making it more accessible to everyone. And that, reader, may ring a bell or two.

Mirror Stimulation: The Hypothesis

The premise of our HHI is two humans interfacing with each other so that one can send brain impulses to control the other human’s arm.

But Gianni needed a slightly different take. What he and Elisa set out to do is make him interface with himself, so that his healthier leg can feed its activity into its less innervated counterpart. Relying on neuroplasticity, their hypothesis would also fall back on mirror stimulation where some of our neurons can be triggered not only by an action, but also by our seeing or even imagining that action. That way, our body can feel an effect even when it isn’t there.

“At first, I tried the HHI on myself to map out the potential electrode placement. Getting nerves on the legs is more complicated than getting them on an arm,” Elisa recounts. When she went to Italy and brought the gift to her dad, the real thing could commence. But thresholds that would give her leg a strong zap just didn’t work for Gianni, not even when they replicated the positioning. They stepped up the thresholds to little avail.

An Engineering Challenge – Accepted!

Amateur scientist Human-Human Interface - experimenting with electrode placement

“In science, you often start by thinking big. But then you have to break down the idea and try to troubleshoot,” says Elisa.

So after countless iterations where they moved the electrodes around in vain, Gianni decided to strip down the HHI to just the TENS stimulator. But the trouble didn’t end there – it turned out that the stimulator itself needed modifying. To be able to tweak the frequency, amplitude and shape of the wave, he shorted it and tried to switch between monophasic and biphasic pulse. To their surprise, the oscilloscope didn’t show any biphasic wave shapes. That higher amplitudes didn’t yield results wasn’t surprising, however. Another device that Gianni tried on his legs does produce higher amplitudes using electromagnetic fields, but the de-innervated leg doesn’t respond to them either.

“We started doing mirror stimulation: On the healthier leg, we’d try to figure out the position where we can get the muscles to respond. Then we’d try to find the exact same position on the other leg. But that was where we hit the roadblock as we couldn’t get past the innervation problem,” Gianni sums it up.

As every scientist knows all too well, every experiment that works follows countless experiments that don’t. So Elisa and Gianni don’t intend to give up.

Their premise isn’t wrong, Elisa posits. While they squeezed every conceivable capability out of a non-invasive stimulator like this, a better outcome could be possible with a different device. One of the standard therapies for spinal cord injury is stimulation of the cord itself rather than the muscles. “If the stimulator could be modified so that it becomes a spinal cord stimulator rather than muscle stimulator, maybe it would work. The electrodes would also have to be much bigger and be placed one in the front, another in the back rather than next to each other,” she concludes. 

Indeed, spinal cord stimulation has been documented to work, but involves implantation directly into the spinal cord, an experimental technique that only neurosurgeons are qualified (rightfully so) to do.

We sure hope our team of engineers will be reading this article! But while they’re at it, there’s one thing we need to ask of you, dear reader. Have you ever tried to do anything similar with our HHI? If yes, do get in touch either with us at or Elisa directly via LinkedIn. It’s not just because we enjoy seeing people hack our gear apart and make it better. It’s also because we all need to foster a community where ideas flow freely to make our lives better!

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