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Groundbreaking study uncovers why humans need sleep

[Jan. 11, 2024: JD Shavit, The Brighter Side of News]

Researchers are shedding light on the complex role of sleep in our brains. (CREDIT: Creative Commons)

Sleep, often considered a mysterious and essential part of our lives, has puzzled scientists for years. While we know that we can't survive without it, the true purpose of sleep remained elusive.

However, a groundbreaking study conducted by a team of researchers at Washington University in St. Louis, led by assistant professor Keith Hengen, is shedding light on the complex role of sleep in our brains.


In a recent publication in Nature Neuroscience, Hengen and his interdisciplinary team unveiled a revolutionary theory that combines concepts from physics and biology to explain the profound significance of sleep.

The researchers argue that sleep serves as a crucial reset button for the brain, allowing it to reach a state of "criticality," which optimizes cognitive functions and information processing.


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"The brain is like a biological computer," explains Hengen. "During waking hours, memory and experiences slowly alter its code, pulling it away from an ideal state. The primary purpose of sleep is to restore the brain to an optimal computational state."

This theory of "criticality" has its roots in the world of physics, where it describes a complex system that teeters on the edge between order and chaos. Ralf Wessel, a professor of physics and co-author of the study, notes that criticality maximizes the encoding and processing of information, making it a compelling principle for understanding neurobiology.


In a previous study in 2019, Hengen and Wessel demonstrated that the brain actively maintains criticality. However, their recent research offers direct evidence that sleep plays a pivotal role in restoring the brain's computational power, challenging the conventional belief that sleep merely replenishes mysterious and unknown chemicals. Hengen and Wessel proposed that learning, thinking, and wakefulness push the brain away from criticality, and sleep acts as the perfect reset mechanism. "Sleep is a systems-level solution to a systems-level problem," Hengen emphasizes.

Keith Hengen, assistant professor of biology at Washington University in St. Louis. (CREDIT: Washington University in St. Louis)

To test their theory, the researchers monitored the brain activity of young rats during their normal sleep-wake cycles. They observed "neural avalanches," which are cascades of activity reflecting how information flows through the brain. At criticality, avalanches of all sizes occurred, resembling a diverse vocabulary of words in a book.


However, as waking hours progressed, the cascades shifted toward smaller sizes, indicating a departure from criticality. The researchers could even predict when rats were about to fall asleep or wake up based on the distribution of these avalanches.

"The results suggest that every waking moment pushes relevant brain circuits away from criticality, and sleep helps the brain reset," Hengen concludes.

The concept of criticality, initially developed in the field of physics using sandpile models on checkerboard-like grids, surprisingly applies to our brains. Thousands of grains of sand following simple rules can quickly reach a critical state, where complex interactions and avalanches occur. Similarly, the neural avalanches in our brains signify a system that has reached its most intricate state.


Hengen likens neurons to individual grains of sand, following basic rules of firing on or off based on inputs. When billions of neurons reach criticality, they collaborate to create complex and wondrous phenomena in the brain.

Ralf Wessel. (CREDIT: Washington University in St. Louis)

This groundbreaking study is the result of a beautiful collaboration between physics and biology. Hengen, Xu, Schneider, and Wessel joined forces to design experiments, collect data, and implement mathematical equations that bridge the gap between these two disciplines.


This discovery opens new avenues for understanding the intricacies of sleep and its profound impact on our daily lives. The brain's ability to reset itself during sleep might just be the key to unlocking the secrets of optimal thinking and processing.

For more science news stories check out our New Discoveries section at The Brighter Side of News.


Note: Materials provided above by The Brighter Side of News. Content may be edited for style and length.


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