Neuroscientists listened in on people’s brains for a week. They found order and chaos.

Our brains exist in a state somewhere between stability and chaos as they help us make sense of the world, according to recordings of brain activity taken from volunteers over the course of a week. As we go from reading a book to chatting with a friend, for example, our brains shift from one semi-stable state to another-but only after chaotically zipping through multiple other states in a pattern that looks completely random.

Understanding how our brains restore some degree of stability after chaos could help us work out how to treat disorders at either end of this spectrum. Too much chaos is probably what happens when a person has a seizure, whereas too much stability might leave a person comatose, say the neuroscientists behind the work.

A better understanding of what's going on could one day allow us to use brain stimulation to tip the brain into a sweet spot between the extremes.

A week in the brain

Brain imaging techniques have revealed a lot about how the brain works-but there's only so much you can learn by getting a person to lie still in a brain scanner for half an hour. Avniel Ghuman and Maxwell Wang at the University of Pittsburgh wanted to know what happens in the longer term. After all, the symptoms of many neurological disorders can develop over hours or days, says Wang. To get a better idea of what might be going on, the pair devised an experiment that would let them watch brain activity for around a week.

Ghuman, Wang, and their colleagues turned to people who were undergoing brain surgery for epilepsy. Some people with severe or otherwise untreatable epilepsy opt to have the small parts of their brain that trigger their seizures surgically removed. Before any operation, they may have electrodes implanted in their brains for a week or so. During that time, these electrodes monitor brain activity to help surgeons pinpoint where their seizures start and identify exactly which bit of brain should be removed.

The researchers recruited 20 such individuals to volunteer in their study. Each person had 10 to 15 electrodes implanted for somewhere between three and 12 days.

The pair collected recordings from the electrodes over the entire period. The volunteers were all in hospital while they were monitored, but they still did everyday things like eating meals, talking to friends, watching TV, or reading books. We know so little about what the brain does during these real, natural behaviors in a real-world setting," says Ghuman.

The edge of chaos

The team found some surprising patterns in brain activity over the course of the week. Specific brain networks seemed to communicate with each other in what looked like a dance," with one region appearing to listen" while the other spoke," say the researchers, who presented their findings at the Society for Neuroscience annual meeting in San Diego last year.

And while the volunteers' brains seemed to pass between different states over time, they did so in a curious way. Rather than simply moving from one pattern of activity to another, their brains appeared to zip between several other states in between, apparently at random. As the brain shifts from one semi-stable state to another, it seems to embrace chaos.

It makes sense, says Rick Adams, a psychiatrist and neuroscientist at University College London, who was not involved in the work. There's probably no central node that tells the rest of the brain what to do," he says. It's a bit like shaking a snow globe-you introduce some random variation and trust that if it goes through a bunch of configurations, the optimal one will pop out somehow."

There are stable states, and then there are unpredictable, volatile transitions," says Hayriye Cagnan, a neuroscientist at the University of Oxford, who was not involved in the research. If we can figure out the pattern associated with a healthy brain, we might be able to use electrical stimulation to treat neurological disorders, she says.

That's what Ghuman hopes. Healthy patterns of brain activity are somewhere on the edge of order and disorder," he says. This may be an optimal place for the brain to be."

The results don't yet tell us what a healthy brain functioning in a natural environment might look like. After all, all the volunteers were in the hospital, waiting for brain surgery to treat their severe seizures. But the team hopes that their study provides the first step to figuring this out.

The approach could help us develop better treatments for epilepsy, too. Some people opt to have electrodes implanted in their brains that sense when a seizure is starting and deliver a pulse of electricity to head them off. These devices aren't perfect, though. They might work better if they were developed to recognize these chaotic transitions and nudge the brain into a place between chaos and stability, suggests Kelly Bijanki, a neuroscientist at Baylor College of Medicine in Houston, Texas.

In the future, Ghuman and Wang hope to use the same approach to find out what happens in children's brains and whether it differs from the activity seen in adults. They also hope to learn more about how our brains change over the course of a day or a week, and how this is linked to our body's circadian rhythms.