The electrified brain: the power and promise of neural implants

100,000 people are living with brain stimulation implants. But can the devices do more than cure the sick?


In 2007, in the middle of a 12-hour nursing shift at New York-Presbyterian Hospital in Manhattan, Rebecca Serdans noticed something was wrong. "It always starts with pain," she says — a hot, radiating pain growing from the base of her skull. Serdans suffers from a neurological disorder called dystonia that, when untreated, leaves her with debilitating muscle pain and movement problems. She keeps it in check with a deep brain stimulation (DBS) device. This pacemaker for the brain works by sending a steady electrical pulse into her globus pallidus. When it's functioning properly, this pulse lets her walk without tripping and move through the world without pain. Only now, years after it was installed, it wasn't working. She could feel it. Serdans began the surreal process of troubleshooting her electrically enhanced brain.

After receiving the implant, she'd been given a booklet of things that might deactivate the device, like strong magnetic fields or running microwaves. Some patients even reported trouble from the battery of a hybrid car. But she hadn't been near a microwave. She hadn't even been near a car. Still, she could feel the pain begin to build as her muscles grew stiff.

The trouble was coming from something she couldn’t even see, reaching through the wall of the intensive care unit. It was an MRI machine in the adjacent room, generating a magnetic field powerful enough to deactivate her implant from thirty feet away. She’d never been warned about machines in the next room. After finishing out her shift in pain, she went back to her doctor to have the unit reset, and the symptoms began to disappear. She returned to the hospital with doctor's orders to avoid that ICU, but over the next two months, her device was switched off three more times. After the fourth shutoff, she staggered home and blacked out.

"I still don't know what I did for those four days," she says.

After nearly 20 years as a nurse, Serdans wasn't safe in hospitals anymore. There were too many loose magnetic fields and disruptive forces, and her supervisors offered little help navigating it. They didn’t understand the MRI problem, or why their nurse was suddenly refusing to work in one of their ICUs.

"They have to learn how to accommodate this new set of bionic people," Serdans says. "Because that's what we are."


There are over 100,000 people currently living with DBS brain implants; most are being treated for symptoms of Parkinson’s disease. The device itself is simple, just a pair of wires connected to a battery pack implanted beneath the skin. It’s not a cure, but by sending small electrical shocks to the regions of the brain that govern movement, doctors are able to keep the tremors of Parkinson’s in check. Other movement disorders like Rebecca Serdans’ dystonia respond the same way. With a pair of wires, five years of declining motor control can be reversed.

With a pair of wires, five years of declining motor control can be reversed

Every patient remembers getting the surgery, for the simple reason that they’re awake when it happens. They need to be. The human brain is so varied that the only way surgeons can navigate it is by testing the effects of an electric pulse on different regions. For instance, one center might paralyze the left half of your body, while another produces global aphasia, leaving you unable to form words. The surgeons create a kind of roadmap to the brain that helps guide them to the optimal placement. On one occasion, a doctor at UCLA went so far as to broadcast the procedure in real time on Twitter. The patient even brought a guitar and strummed it as the surgery went along. He wanted to be sure he would still be able to play it on the other side.

The results are as reliable as flipping a light switch, but even after decades of testing, no one knows exactly why it works. Dr. Kaplitt, the surgeon who installed Rebecca Serdans’ implant, explains it by likening the brain to a collection of electrical circuits. A disorder like dystonia is a failure of those circuits. When you install a brain stimulation device, “it's presumably blocking abnormal information from getting from one part of the brain to another, or normalizing that information.” But Kaplitt is the first to acknowledge that this is just a theory. “The mechanism by which brain stimulation works is still somewhat unclear and controversial.”

But the lingering questions haven’t slowed down research. There are already patents that would use brain stimulation implants to enhance memory or prevent stuttering, to cure anorexia or bring a person to orgasm. Experimental studies use the device to treat Alzheimer’s disease and drug addiction. Those circuits aren’t as well understood as the circuits governing movement disorders, but the principle is no different. Once you’ve got a line into the circuitry of the brain, Parkinson’s is just the beginning.

"I really think that brain stimulation in psychiatry is the biggest revolution in the last 50 years."

At the same time, the economic incentives are undeniable. Medtronic, the largest brain stimulation device manufacturer, made $1.7 billion from the implants last year. This has prompted a search for more ways to use the device, including a seizure-sensing model that preemptively responds to epileptic attacks, which is slated to begin human trials this year.

Psychiatrists are also finding uses for the technology. At the University of Bonn in Germany, Dr. Thomas Schlaepfer is using the implant to treat severe depression. Instead of the movement centers, Schlaepfer's treatment targets the brain’s reward centers, taking depression as a malfunction of the neurological reward mechanism. “I really think that brain stimulation in psychiatry is the biggest revolution in the last 50 years,” he says, “because it offers some hope for patients who had little or nothing to hope for.”

Schlaepfer makes a point of saying he’s trying to restore the brain to normal function, but it’s not the only place his research could go. He admits that a less ethical scientist could use the device to create a state of constant reward, something he calls "heroin in electrical form." It wouldn’t be useful in treating depression, but it would be as simple as reprogramming the device, and it would take just half an hour in a doctor’s office.

Why stop at curing the sick? If we can restore memory to an Alzheimer’s patient, why not target the same circuit to enhance a person’s recall to superhuman levels? Researchers can already guess where the centers for enhanced memory or improved cognition are, and it’s easy to imagine treatments that might boost attention or trigger bursts of verbal fluency. Neuroenhancement, as it's called, has been a common topic for thought experiments, but brain stimulation could someday make it a reality.

The idea has been around since physiologist José Delgado demonstrated the first versions of brain stimulation technology in the 1960s. Using a remote control to stop a bull mid-charge, he thought he’d found the neurological origins of aggression. Later experiments determined stimulation targets that could create sexual arousal, deja vu, and in Delgado’s words, “Both shame and true rage.” In 1969, he wrote a book-length treatise called Physical Control of the Mind: Toward a Psychocivilized Society. It envisioned neurostimulation’s possibilities on a societal scale, where it could be used “to create a future man with greater personal freedom and originality, a member of a psychocivilized society, happier, less destructive, and better balanced than present man.” As research advanced, and methods became more rigorous and scientific, many of Delgado's conclusions were rejected (for instance, there is no “shame center” in modern neuroscience). These days, Delgado is seen as an embarrassing predecessor to modern brain stimulation research, and he's remembered as being too eccentric to be taken at his word.

"a member of a psychocivilized society, happier, less destructive, and better balanced than present man."

While Delgado's work remains controversial, many of his ideas on neuroenhancement now seem far more plausible than they once were. Dr. Schlaepfer, for instance, doesn’t think that deep brain stimulation will stay confined to the medical world for long. We’ve been building better brains for years, the argument goes, whether through short-term fixes like a cup of coffee or long-term training like multiplication table drills. As long as the procedure is done with informed consent, there’s no reason neuroenhancement should be any more troubling. If depression could be treated in 12 hours using an implant instead of 12 months using prescribed medication, most ethicists would argue it’s a good thing. If patients find the effects unpleasant, they could simply turn the implant off.

The biggest roadblock to widespread use of brain stimulation is the surgery required to implant the device. It’s expensive and there’s an element of danger any time a foreign object is implanted in the human body. But it may not always be that way. "Right now, DBS is only a 'halfway' technology," Schlaepfer says, and as the technology improves, it will become less invasive. Experimental methods like targeted ultrasound or electrode treatment ELE could achieve the same effect without running wires directly into the skull. When this happens, doctors might not be necessary at all.

For patients living with chronic illness, mind control and electrical heroin are the least of their worries. They’re more concerned with the routines of medical treatment: tracking symptoms and looking for signs of recovery. Nearly all of the patients I spoke to had a story about how much they’d lost to their illness, and how brain stimulation had helped them get some of it back.

At 44 years old, Joe Narciso was taking 19 pills a day before his implant. He took the usual Parkinson’s pills, and a separate battery of tremor pills. The Parkinson’s pills left him wired and unable to sleep, so he took sleeping pills. The chemical cocktail left him feeling drowsy and foggy on top of the lingering Parkinson’s symptoms. Compared to that regimen, brain stimulation is remarkably low-impact. He's also using the implant to target symptoms there aren’t drugs for. Before Parkinson’s, he’d been a voice actor with 2,500 commercials under his belt, but the disease turned his voice into a husky whisper. Now he’s looking for a combination of voltage and frequency that will get him his old voice back, even if it comes at the expense of motor control. That’s a tradeoff that would be impossible in a pharmaceutical regimen, but brain stimulation could be versatile enough to pull it off.

Another Parkinson’s patient who asked not to be named came to brain stimulation after experiencing terrible side effects from Mirapex, a Parkinson’s drug found to cause impulse control problems. In her case, that meant both gambling addiction and compulsive sexual addiction. She experienced some side effects with brain stimulation, but nothing close to Mirapex. As unsettling as the thought of a brain implant was, it turned out to be safer than pills.

Dee Linde had such severe dystonia that she could barely lift herself from the floor. The implant gave her back her mobility, but left her with profound questions about what brain stimulation meant. If she couldn’t live without the implant, she asked, what did it say about the body and brain she was born with? “The doctors are very good at preparing you for what to expect physically, but not psychologically,” she says. “Eventually," Linde decided, "I don't care what they put in me. If I'm gonna get my life back, they could fill me full of batteries and I don't care. As long as I can function.”

"I don't care what they put in me. If I'm gonna get my life back, they could fill me full of batteries and I don't care. As long as I can function.”

Rebecca Serdans, for her part, is living with the same questions. She's back to work, making house calls on the Upper East Side and avoiding hospitals entirely. "DBS gives you some function back, but it doesn't give you everything back," she tells me. Her voice is strained, and she worries that it puts people off. She still has trouble turning her body to the right, which keeps her from driving, so when we walk down the street, she asks me to stay to her left.

Brain stimulation has also drawn her into a legal fight. She’s suing her former employer, New York-Presbyterian Hospital under state anti-discrimination laws, hoping to establish the implant as a legal disability. The effects of the MRI machine were surprising, but they're not rare. She still has to be careful of magnetic fields and the other complications of life as a bionic person. She's worried about the new fleet of hybrid taxis, and what effect they'll have on her implant.

In some moments, she feels guilty for how well the treatment works. She tells me about the days before the implant, when she was relying on botox injections in her back that were growing increasingly less effective. At the time, she was studying nights at Hunter College for her nursing degree, and after a while the tremors were so bad that she couldn’t pass the physical exams. It took brain stimulation to still her tremors enough to get her through her finals, and get her the certification she needed. Even now, exiled from hospital work, the implant has still given Serdans more than it’s taken away.

Isn't it strange? I ask. Living with wires and an implant, checking your battery level every week? Doesn't it seem… not normal?

"I forgot what normal was," she says with a smile. "I don't even remember it."

Photography by Michael Shane
Infographic designed by Kelsey Scherer and Scott Kellum

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