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The Checkup: What minimally conscious brains can do

Hello, and welcome to this first edition of The Checkup!

Every week I’ll be covering what I think are the most exciting, fascinating, and controversial developments in health, medical science, and biotech—and how they might help diagnose, treat, enhance, or even harm us. Thanks for joining me! (If you want to be among the first people to read these posts, make sure you sign up to the newsletter here.)

This week I’ve been thinking about consciousness. Specifically, what are our brains doing when we’re unconscious? And is there a way to restore consciousness in a person who has lost it? (You can read more about the mysteries of the mind in our Mind issue from last year.)

I’d come across a new study suggesting that people in a minimally conscious state can learn a rudimentary form of language, or at least a string of previously unknown syllables.It sounded fascinating, so I called up John Whyte, who has spent much of his career studying disorders of consciousness. Whyte is the perfect person to speak to about this sort of thing, and he has so many mind-blowing insights and anecdotes.

Right at the start of our call, he told me that in many ways, the brains of minimally conscious people behave similarly to those of conscious people, despite their being unable to consistently communicate or be aware of their surroundings. He also told me about some fascinating—and tear-jerking—attempts to pull people in this state back into consciousness. I’ll come back to those in a moment.

This kind of research is really tricky to do in people who are minimally conscious or in an unresponsive wakefulness state, previously known as a vegetative state. Both of these are different from being in a coma. Minimally conscious people show unreliable flickers of awareness and can communicate, but inconsistently. But people in an unresponsive wakefulness state can’t communicate at all. 

People in either state experience periods of sleep and waking, while those in a coma show no signs of being awake.

Amazing brains 

In this study I’d seen, Nai Ding at Zhejiang University in Hangzhou, China, used a cap of electrodes to record the brain activity of people in a minimally conscious state. When his team played audio of familiar words, the participants’ brains showed waves of activity for entire words as well as their individual syllables, suggesting that they recognized each word.

But when the team played new, made-up words, the patterns of activity suggested that they only processed the words as individual syllables.

To “teach” the participants the words, Ding and his colleagues played the new words over and over, thousands of times. By the end of the experiment, the participants showed waves of brain activity for the entire words, just as they did with familiar real words. This suggests that they’d learned the new words. 

“They are not even conscious, but they preserve some ability to learn”

Nai Ding of Zhejiang University in Hangzhou, China

“They still have the potential to learn words in a new language,” Ding told me. “I think that’s amazing … they are not even conscious, but they preserve some … ability to learn.” Of course, they are not learning in the same way that school children learn new words—by reading and writing them, and using them in speech. But their brains have learned to make new associations.

Incredibly, this isn’t the first time that people in a minimally conscious state, or even an unresponsive wakefulness state, have shown some capacity to learn. Other teams have shown, for example, that people in a minimally conscious state can learn to associate a beeping sound with air being puffed into their eyes, and will eventually blink on hearing the sound alone.

What does this tell us? For a start, it highlights just how amazing our brains are. But it also illustrates how difficult it is to understand exactly what consciousness is and how our brains work. The neuroscientists who undertake this research hope to find ways of helping those who aren’t fully conscious. Ding, for example, hopes that his word learning technique will encourage people’s brains to become more “plastic,” creating new connections that might help them recover.

But we don’t yet know whether this ability to learn makes recovery more likely—or is beneficial in any way.

Bringing people back

Of the hundreds of thousands of people with disorders of consciousness, only a fraction will recover. The precise figure depends on why they lost consciousness—the outlook is better for those who survive traumatic brain injuries than those who had a loss of blood flow to the brain. The longer a person spends unconscious, the less likely recovery becomes. Which is one reason why multiple research groups are trying to find ways to pull people back into consciousness.

Some of these attempts involve inserting electrodes deep into the brain to reach a structure called the thalamus. This structure is thought to be part of the brain’s “seat of consciousness.”  Zapping the brain in this way has helped to rouse a small number of people in the past

Even drugs can work, albeit temporarily, for a small proportion of people. Whyte, a now semi-retired neuroscientist at the Moss Rehabilitation Research Institute in Elkins Park, Philadelphia, told me about his research into a drug called amantadine. The drug is used to treat Parkinson’s disease, but some neurologists had experimented with using it in minimally conscious patients.

When Whyte and his colleagues trialed it in 184 people in a minimally conscious or unresponsive (vegetative) state, they found that the drug could help speed up recovery—those taking the drug were faster to show signs of improvement, such as being able to respond to questions or use objects.

Another drug, zolpidem, appears to rapidly rouse a small fraction of cases, says Whyte. He remembers a young man who had sustained a head injury on his way home from his summer vacation. The man had been completely unconscious for three years. But within an hour of being given the drug, he started to show signs of consciousness— he even waved and hugged his parents.

Devastatingly, the improvements lasted only a few hours. And Whyte was in tears when he recalled how the drug started to lose its effectiveness. In the end, the family decided to save the drug for special occasions so they could wake their son when his grandmother visited, for example.

Cases like these provide heartbreaking and fascinating insight into the complicated and fragile nature of human consciousness, and the potential—or lack thereof—for technologies to help us understand or restore it. To find out more about some of these attempts, you can check out the following stories from Tech Review’s archive:

  • Raising consciousness, by Emily Singer, describes technologies revealing that the brains of people in a minimally conscious state respond to stories in a similar way to healthy brains, and that they can use their thoughts to communicate to some degree.

Solving the organ shortage problem

Last week saw the millionth organ transplant performed in the US, according to the United Network for Organ Sharing. The first organ ever to be transplanted was the kidney, back in the 1950s. But organ donation really took off in the decades that followed—more than half of all organ transplants in the US have been performed since 2007, and 41,000 were performed last year alone, according to the organization.

It sounds like a lot, but it’s unfortunately significantly short of what’s needed. Over 100,000 people in the US are on the national transplant waiting list, and 17 people die every day waiting for a transplant.

Research teams and biotech companies are working on a range of new technologies to solve the problem. Lygenesis, for example, is about to start a trial that will involve growing multiple new mini livers inside people’s bodies. Renewal Bio is attempting to grow organs for transplantation in synthetic embryos. Others are finding ways to rescue damaged organs, with the hope of either reducing the need for donated organs or making more organs fit to be donated to others. Researchers at Yale have shown they can keep a pig’s brain cells working to some degree an hour after the animal has died. And the start of the year brought the explosive news that doctors had transplanted a gene-edited pig heart into a person for the first time. (The recipient, David Bennett Sr., died two months after the operation, and my colleague Antonio Regalado reported that the organ was infected with a pig virus.)

From around the web

  • People across the Northern Hemisphere are gearing up for flu season, and it’s difficult to predict just how hard it will hit.
    – Flu has bounced back in the Southern Hemisphere, which doesn’t bode well for those of us in the North (The Atlantic $)
    – But getting your flu shot as soon as possible, alongside a covid booster, may not be in your best interest (STAT)
     
  • I don’t think I know anybody who hasn’t had covid by now. But some people appear to have escaped infection. Scientists are trying to work out what exactly is protecting them. (Wired $)
     
  • Thousands of women claim that talc in Johnson & Johnson’s baby powder gave them cancer. Not all legal cases have been successful, but in those that have, the company’s payouts have been huge. This long read explores the company’s checkered history, as well as its new strategy to avoid financial compensation. (New Yorker $)
     
  • Poorer countries are missing out on vaccines and treatments for monkeypox. (You’d have hoped we’d have learned about the importance of equitable access to vaccines by now, but it seems not.) (NYT $)
     
  • Given that millions of people have long covid— at least 17 million in the European region alone, according to the latest figures from the World Health Organization— it’s vital we get to grips with one of the most debilitating symptoms: brain fog. (The Atlantic $)

That’s it for this week. If you made it this far, thank you for reading!

Jess

Correction: The drug that roused the young man in John Whyte’s care was zolpidem, not amantadine

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