Even Awake, Our Brains Rest and Activate During Sleep

Scientists have made a groundbreaking discovery: a small region of our brain shuts down briefly to take microsecond-long naps while we’re awake. Interestingly, these same areas become active during sleep. These findings could provide crucial insights into neurodevelopmental and neurodegenerative diseases associated with sleep disturbances.

Researchers from Washington University in St. Louis (WashU) and the University of California Santa Cruz (UCSC) stumbled upon these findings unexpectedly. They observed brain waves in a specific tiny area of the brain abruptly shutting down for milliseconds during wakefulness and flickering awake for the same duration during sleep.

Keith Hengen’s Perspective on States in Behavior

Keith Hengen, Assistant Professor of Biology at WashU, emphasized the potential of challenging fundamental assumptions and reevaluating the concept of ‘what is a state?’ with advanced tools and computational methods. “Sleep or wake is the primary determinant of behavior, shaping everything else. If we don’t truly understand these states, it feels like we’re missing a crucial aspect,” he explained.

Traditionally, sleep and wake states have been defined by overall brain wave patterns — alpha, beta, and theta waves during wakefulness, and delta waves during sleep. However, these ‘flicker’ anomalies challenge existing understandings of these distinct states.

David Haussler, Professor of Biomolecular Engineering at UCSC, humorously remarked, “It was surprising for us scientists to discover that different parts of our brains take brief naps while the rest remains awake, although this may not be news to some spouses.”

Four-Year Study on Brain-Wave Voltage and Neuron Activity in Mice

In a comprehensive four-year study involving extensive electrophysiology data collection, researchers monitored brain-wave voltage across 10 brain regions in mice. They meticulously tracked neuron activity down to the microsecond level over several months. Using advanced artificial neural network analysis of petabytes of data, they identified patterns and isolated microsecond anomalies that had eluded previous human studies.

“We’re observing information at an unprecedented level of detail,” Haussler noted. “Previous assumptions suggested that no significant findings would emerge at this scale, believing all pertinent information resided in slower frequency waves. However, our study indicates that by focusing on high-frequency measurements over extremely brief periods, we can discern whether tissue is in a state of sleep or wakefulness. This insight hints at rapid-scale processes potentially underlying sleep mechanisms.”

Machine Learning Insights into Brain Activity Patterns

Using machine learning, researchers focused on millisecond intervals of brain activity data and identified rapid activity between specific neurons in one region that contradicted traditional slow delta waves typically associated with sleep. Conversely, they observed a different pattern of activity during periods conventionally defined as wakefulness, which they termed ‘flickers.’

“We removed all the traditional information neuroscience has relied on to study and define sleep for the past century, and asked, ‘Can the model still learn under these conditions?‘” explained David Parks, a researcher at UCSC. “This allowed us to delve into signals that were previously misunderstood.”

Essentially, the data indicated that even during wakefulness, a few neurons in this small brain region switched to a sleep-like mode, while the remainder of the brain functioned normally.

“We examined the exact moments when these neurons fired, clearly showing they were transitioning to a different state,” said Aidan Schneider, a researcher at WashU. “In some instances, these flickers were confined to an individual brain region, possibly even smaller.”

Physical Responses During Split-Second Micro-Naps

The researchers then investigated any observable physical responses during these split-second micro-naps. They were surprised to observe brief moments where mice seemed to ‘zone out’ during wakefulness, and twitched during sleep at these ‘flicker’ occurrences.

“We’ve observed flickers from wake to REM, REM to non-REM, and various other combinations, defying expectations based on a century of literature,” noted Hengen. “These findings reveal the disconnect between the macro-state—sleep and wake at the level of the whole organism—and the fundamental unit of state in the brain—the rapid and localized patterns.”

These discoveries may yield fresh insights into conditions linked to disrupted sleep, potentially offering new therapeutic avenues for neurodevelopmental and neurodegenerative diseases.

“This gives us a potentially powerful tool to dissect these questions about diseases and disorders,” Hengen emphasized. “The more we grasp the fundamental nature of sleep and wakefulness, the better equipped we are to address clinical and disease-related challenges.”

Read the original article on: New Atlas

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