NEUROTECHNOLOGY has long been a favourite of science-fiction writers. In “Neuromancer”, a wildly inventive book by William Gibson written in 1984, people can use neural implants to jack into the sensory experiences of others. The idea of a neural lace, a mesh that grows into the brain, was conceived by Iain M. Banks in his “Culture” series of novels. “The Terminal Man” by Michael Crichton, published in 1972, imagines the effects of a brain implant on someone who is convinced that machines are taking over from humans. (Spoiler: not good.)

Where the sci-fi genre led, philosophers are now starting to follow. In Howard Chizeck’s lab at the University of Washington, researchers are working on an implanted device to administer deep-brain stimulation (DBS) in order to treat a common movement disorder called essential tremor. Conventionally, DBS stimulation is always on, wasting energy and depriving the patient of a sense of control. The lab’s ethicist, Tim Brown, a doctoral student of philosophy, says that some DBS patients suffer a sense of alienation and complain of feeling like a robot.

To change that, the team at the University of Washington is using neuronal activity associated with intentional movements as a trigger for turning the device on. But the researchers also want to enable patients to use a conscious thought process to override these settings. That is more useful than it might sound: stimulation currents for essential tremor can cause side-effects like distorted speech, so someone about to give a presentation, say, might wish to shake rather than slur his words.

Giving humans more options of this sort will be essential if some of the bolder visions for brain-computer interfaces are to be realised. Hannah Maslen from the University of Oxford is another ethicist who works on a BCI project, in this case a neural speech prosthesis being developed by a consortium of European researchers. One of her jobs is to think through the distinctions between inner speech and public speech: people need a dependable mechanism for separating out what they want to say from what they think.

That is only one of many ethical questions that the sci-fi versions of brain-computer interfaces bring up. What protection will BCIs offer against neural hacking? Who owns neural data, including information that is gathered for research purposes now but may be decipherable in detail at some point in the future? Where does accountability lie if a user does something wrong? And if brain implants are performed not for therapeutic purposes but to augment people’s abilities, will that make the world an even more unequal place?

From potential to action

For some, these sorts of questions cannot be asked too early: more than any other new technology, BCIs may redefine what it means to be human. For others, they are premature. “The societal-justice problem of who gets access to enhanced memory or vision is a question for the next decades, not years,” says Thomas Cochrane, a neurologist and director of neuroethics at the Centre for Bioethics at Harvard Medical School.

Brain-computer interfaces may redefine what it means to be human

In truth, both arguments are right. It is hard to find anyone who argues that visions of whole-brain implants and AI-human symbiosis are impossible to realise; but harder still to find anyone who thinks something so revolutionary will happen in the near future. This report has looked at some of the technological difficulties associated with taking BCIs out of the lab and into the mainstream. But these are not the only obstacles in the way of “brain mouses” and telekinesis.

The development path to the eventual, otherworldly destination envisaged by organisations like Neuralink and Kernel is extremely long and uncertain. The money and patience of rich individuals like Elon Musk and Bryan Johnson can help, but in reality each leg of the journey needs a commercial pathway.

Companies such as CTRL-Labs and Neurable may well open the door to consumer applications fairly quickly. But for invasive technologies, commercialisation will initially depend on therapeutic applications. That means overcoming a host of hurdles, from managing clinical trials to changing doctors’ attitudes. Frank Fischer, the boss of NeuroPace, has successfully negotiated regulatory approval for his company’s epilepsy treatment, but it has been a long, hard road. “If we tried to raise money today knowing the results ahead of time, it would have been impossible to get funded,” he says.

Start with regulation. Neural interfaces are not drugs but medical devices, which means that clinical trials can be completed with just a handful of patients for proof-of-principle trials, and just a couple of hundred for the trials that come after that. Even so, ensuring a supply of patients for experiments with invasive interfaces presents practical difficulties. There is only one good supply of these human guinea pigs: epilepsy patients who have proved unresponsive to drugs and need surgery. These patients have already had craniotomies and electrodes implanted so that doctors can monitor them and pinpoint the focal points of their seizures; while these patients are in hospital waiting for seizures to happen, researchers swoop in with requests of their own. But the supply of volunteers is limited. Where exactly the electrodes are placed depends on clinical needs, not researchers’ wishes. And because patients are often deliberately sleep-deprived in order to hasten seizures, their capacity to carry out anything but simple cognitive tasks is limited.

When it comes to safety, new technologies entail lengthier approval processes. Harvard’s Dr Lieber says that his neural mesh requires a new sterilisation protocol to be agreed with America’s Food and Drug Administration. Researchers have to deal with the question of how well devices will last in the brain over very long periods. The Wyss Centre has an accelerated-ageing facility that exposes electrodes to hydrogen peroxide, in a process that mimics the brain’s immune response to foreign objects; seven days’ exposure in the lab is equivalent to seven years in the brain.

The regulators are not the only people who have to be won over. Health insurers (or other gatekeepers in single-payer systems) need to be persuaded that the devices offer value for money. The Wyss Centre, which aims to bow out of projects before devices are certified for manufacturing, plans with this in mind. One of the applications it is working on is for tinnitus, a persistent internal noise in the ears of sufferers which is often caused by overactivity in the auditory cortex. The idea is to provide an implant which gives users feedback on their cortical activity so that they can learn to suppress any excess. Looking ahead to negotiations with insurers, the Wyss is trying to demonstrate the effectiveness of its implant by including a control group of people whose tinnitus is being treated with cognitive behavioural therapy.

That still leaves two other groups to persuade. Doctors need to be convinced that the risks of opening up the skull are justified. Mr Fischer says that educating physicians proved harder than expected. “The neurology community does not find it natural to think about device therapy,” he says.

Most important, patients will have to want the devices. This is partly a question of whether they are prepared to have brain surgery. The precedents of once-rare, now-routine procedures such as laser eye and cosmetic surgery suggest that invasiveness alone need not stop brain implants from catching on. More than 150,000 people have had electrodes implanted for deep-brain stimulation to help them control Parkinson’s disease. But it is also a matter of functionality: plenty of amputees, for example, prefer simple metal hooks to prosthetic arms because they are more reliable.

Waiting for Neuromancer

These are all good reasons to be cautious about the prospects for BCIs. But there are also reasons to think that the field is poised for a great leap forward. Ed Boyden, a neuroscientist at MIT who made his name as one of the people behind optogenetics, points out that innovations are often serendipitous—from Alexander Fleming’s chance discovery of penicillin to the role of yogurt-makers in the development of CRISPR, a gene-editing technique. The trick, he says, is to engineer the chances that serendipity will occur, which means pursuing lots of paths at once.

That is exactly what is now being done with BCIs. Scientific efforts to understand and map the brain are shedding ever more light on how its activity can be harnessed by a BCI and providing ever more data for algorithms to learn from. Firms like CTRL-Labs and Neurable are already listening to some of the more accessible neural signals, be it from the peripheral nervous system or from outside the skull. NeuroPace’s closed-loop epilepsy system creates a regulatory precedent that others can follow. Above all, researchers are working hard on a wide range of new implants for sending and receiving signals to and from the brain. That is where outfits like Kernel and Neuralink are focused in the short term. Mr Musk’s four-year schedule for creating a BCI for clinical use is too ambitious for full clinical trials to be concluded, but it is much more realistic for pilot trials. This is also the rough timeframe to which DARPA is working with its implantables programme. With these and other efforts running concurrently, serendipity has become more likely. Once a really good, portable, patient-friendly BCI is available, it is not hard to think of medical conditions that affect a large number of people and could potentially justify surgery. More than 50m people worldwide suffer from epilepsy, and 40% of those do not respond to medication. Depression affects more than 300m people worldwide; many of them might benefit from a BCI that monitored the brain for biomarkers of such mental disorders and delivered appropriate stimulation. The quality of life of many older people suffering from dysphagia (difficulty in swallowing) could be improved by a device that helped them swallow whenever they wanted to. “A closed-loop system for recording from a brain and responding in a medically useful way is not a small market,” says Dr Hochberg. That may still bring to mind the aphorism of Peter Thiel, a Silicon Valley grandee, about having been promised flying cars and getting 140 characters. There is a large gap between dreamy talk of symbiosis with AI, or infrared eyesight, and taking years to build a better brain implant for medical purposes. But if a device to deliver a real-time, high-resolution, long-lasting picture of neural activity can be engineered, that gap will shrink spectacularly.

Drs Anikeeva, Chizeck and Fetz are all members of the Centre for Sensorimotor Neural Engineering, a research hub headquartered at the University of Washington and funded by America's National Science Foundation.