Research offers the first concrete explanation for why humans sleep

In a study that combines biology and physics, researchers have offered the first concrete explanation for why humans sleep. According to their theory, which treats the brain like a biological computer whose resources are depleted while awake, sleep restores the brain’s “operating system,” putting it back in a condition that maximizes thinking and processing.

Why do we sleep is a question that has long baffled scientists and experts. What is achieved by meeting this basic need? You can find a variety of responses to the question “why do we sleep” on Google from different sites. Sleep is essential for the creation of long-term memories, according to others, and it helps the body heal and replenish itself. Still others claim that sleep clears poisons from the brain.

In mice, activating specific brain cells prolongs life and reduces aging.
Researchers at Washington University in St. Louis have now offered the first concrete proof that could address the query in their study.

According to the study’s corresponding author Keith Hengen, “the brain is like a biological computer.” “Memory and experience during waking change the code bit by bit, slowly pulling the larger system away from an ideal state. The central purpose of sleep is to restore an optimal computational state.”

It is not too much of a stretch to compare the brain to an intricate computer. Our neurons are similar to circuitry, long-term memory is like a hard drive for storing and retrieving information, and both rely on electrical signals to carry information. A computer’s performance may gradually decrease as a result of the numerous resource-hogging processes that are performed in the background when it is being used. Based on the “criticality hypothesis,” the researchers of the present study postulated that the brain functions in a comparable manner.

Co-author of the paper Ralf Wessel stated, “The whole system organizes itself into something extremely complex.”

The researchers apply the criticality hypothesis to the brain and compare each neuron to a single grain of sand that adheres to a set of extremely fundamental laws. Similar to the sand avalanches that physicists have constructed, neural avalanches are characterized by cascades, which indicate that a system has attained its highest complicated state. Neurons can achieve criticality—a state where information processing in the brain is optimized—if they can find the ideal balance between excessive order and chaos.

The brain actively maintains criticality, as demonstrated by Hengen and Wessel’s 2019 exploration of the criticality theory. Their team of researchers endeavored to comprehend the role of sleep within the criticality framework in the current investigation. As the juvenile rats freely went about their regular sleep/wake cycles, they recorded the electrophysiological responses of individual neurons in their visual cortices.

According to Hengen, “you can follow these little cascades of activity through the neural network.” “At criticality, avalanches of all sizes and durations can occur. Away from criticality, the system becomes biased toward only small avalanches or only large avalanches. This is analogous to writing a book and only being able to use short or long words.”

When the rats were awoken from restorative sleep, the researchers saw avalanches of different sizes. The cascades grew smaller and smaller while the subject was conscious. The researchers discovered that by monitoring the distribution of neural avalanches, they could determine when the rats were going to fall asleep or wake up. When cascade sizes were lowered to a certain degree, sleep was imminent.

According to Hengen, “the results suggest that sleep helps the brain reset and every waking moment pushes relevant brain circuits away from criticality.”

Overall, the data, according to the researchers, are consistent with a concept in which criticality, which has gradually diminished throughout waking, is restored by sleep. Their findings supported their theory that sleep’s primary restorative function is the preservation of criticality.