Micro-naps in the brain: Some regions sleep while others stay awake

Most people view sleep and wakefulness as two distinct states, clearly separating our daily activities.

Traditional neuroscience has anchored this perspective, defining sleep by the long, slow waves that traverse our brain. Now, pioneering research has unveiled intriguing details that challenge this belief.

The sleeping brain

The researchers have found that sleep can be detected by neural activity patterns lasting for just milliseconds – 1,000 times shorter than a second.

What’s more, they discovered that small areas of the brain could briefly “flicker” awake, while the rest of the brain is asleep, and the opposite can also occur.

These revelations open up fresh avenues to explore and understand the fundamental brain wave patterns that govern consciousness.

The research is a collaboration between the laboratories of Professor Keith Hengen at Washington University in St. Louis and Professor David Haussler at UC Santa Cruz, with crucial contributions from Ph.D. students, David Parks (UCSC) and Aidan Schneider (WashU).

What is a state?

Professor Hengen highlighted the significant implications of their discovery. He said that with powerful tools and new computational methods, there’s so much to be gained by challenging our most basic assumptions and revisiting the question of “what is a state?”

“Sleep or wake is the single greatest determinant of your behavior, and then everything else falls out from there. So if we don’t understand what sleep and wake actually are, it seems like we’ve missed the boat.”

Micro-naps in the brain

Professor Haussler noted that the research revealed different parts of the brain “taking little naps” while other regions remain awake.

“It was surprising to us as scientists to find that different parts of our brains actually take little naps when the rest of the brain is awake. Many people may have already suspected this in their spouse, so perhaps a lack of male-female bias is what is surprising.”

Brain activity patterns by the millisecond

In the course of their four-year research, Parks and Schneider trained a neural network to scrutinize patterns within an enormous amount of brain wave data.

Ultimately, the team observed patterns occurring at extremely high frequencies, challenging foundational beliefs about the neurological basis of sleep and wake states.

Studying brain data that lasted for only a millisecond, the researchers found that the model could differentiate between sleep and wake states. This remarkable finding confirmed that the model wasn’t relying on the slow-moving waves to learn the difference.

“The previous feeling was that nothing would be found there, that all the relevant information was in the slower frequency waves,” said Professor Haussler.

“This paper says if you ignore the conventional measurements and just look at the details of the high-frequency measurement over just a thousandth of a second, there is enough there to tell if the tissue is asleep or not.”

According to Professor Haussler, this tells us that there is something going on a very fast scale – that’s a new hint to what might be going on in sleep.

Uncovering neural “flickers”

Upon further investigation of these high-speed activity patterns, the researchers discovered another surprising phenomenon, which they refer to as “flickers.”

These are instances where, for a split second, one region of the brain would be awake while the rest were asleep, and vice versa.

These flickers don’t adhere to the traditional neuroscience rules governing the strict cycle between wake, non-REM sleep, and REM sleep, further defying standard beliefs on sleep dynamics.

The future of sleep research

These groundbreaking findings pave the way for a deeper understanding and potential treatments of neurodevelopmental and neurodegenerative diseases, both of which are closely associated with sleep dysregulation.

The research holds promise for developing new diagnostic tools and therapies that target the specific neural mechanisms involved in these conditions.

“The more we understand fundamentally about what sleep and wake are, the more we can address pertinent clinical and disease-related problems,” said Professor Hengen.

This knowledge could revolutionize our approach to treating a wide range of disorders linked to sleep, from insomnia and sleep apnea to more complex neurological conditions such as Alzheimer’s and autism.

The study is published in the journal Nature Neuroscience.

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