Waking Up at Night Could Be Your Brain Boosting Your Memory

From Medscape today -

Waking Up at Night Could Be Your Brain Boosting Your Memory

Gina Loveless
August 03, 2022

We tend to think a good night's sleep should be uninterrupted, but surprising new research from the University of Copenhagen suggests just the opposite: Brief awakenings may be a sign you’ve slept well.
The study, done on mice, found that the stress transmitter noradrenaline wakes up the brain many times a night. These "microarousals" were linked to memory consolidation, meaning they help you remember the previous day's events. In fact, the more "awake" you are during a microarousal, the better the memory boost, the research suggests.
"Every time I wake up in the middle of the night now, I think — ah, nice, I probably just had great memory-boosting sleep," says study author Celia Kjaerby, PhD, an assistant professor at the university's Center for Translational Neuromedicine.
The findings add insight to what happens in the brain during sleep and may help pave the way for new treatments for those who have sleep disorders.
Waves of Noradrenaline

Previous research has suggested that noradrenaline — a hormone that increases during stress but also helps you stay focused — is inactive during sleep. So, the researchers were surprised to see high levels of it in the brains of the sleeping rodents.
"I still remember seeing the first traces showing the brain activity of the norepinephrine stress system during sleep. We could not believe our eyes," Kjaerby says. "Everyone had thought the system would be quiet. And now we have found out that it completely controls the microarchitecture of sleep."
Those noradrenaline levels rise and fall like waves every 30 seconds during non-rapid eye movement (NREM) sleep. At each "peak" the brain is briefly awake, and at each "valley" it is asleep. Typically, these awakenings are so brief that the sleeping subject does not notice. But the higher the rise, the longer the awakening — and the more likely the sleeper may notice.
During the valleys, or when norepinephrine drops, so-called sleep spindles occur.
"These are short oscillatory bursts of brain activity linked to memory consolidation," Kjaerby says. Occasionally there is a "deep valley," lasting 3 to 5 minutes, leading to more sleep spindles. The mice with the most deep valleys also had the best memories, the researchers noted."We have shown that the amount of these super-boosts of sleep spindles, and not REM sleep, defines how well you remember the experiences you had prior to going to sleep," says Kjaerby.
Deep valleys were followed by longer awakenings, the researchers observed. So, the longer the valley, the longer the awakening — and the better the memory boost. This means that, though restless sleep is not good, waking up briefly may be a natural part of memory-related sleep phases and may even mean you've slept well.
What Happens in Our Brains When We Sleep: Piecing It Together

The findings fit with previous clinical data that shows we wake up roughly 100-plus times a night, mostly during NREM sleep stage 2 (the spindle-rich sleep stage), Kjaerby says.
Still, more research on these small awakenings is needed, Kjaerby says. She notes that professor Maiken Nedergaard, MD, another author of this study, has found that the brain cleans up waste products through a rinsing fluid system.
"It remains a puzzle why the fluid system is so active when we sleep"” Kjaerby says. "We believe these short awakenings could potentially be the key to answering this question."
Sources

Celia Kjaerby, PhD, assistant professor, Center for Translational Neuromedicine, University of Copenhagen.
Nature Neuroscience: "Memory-enhancing properties of sleep depend on the oscillatory amplitude of norepinephrine."

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Interesting how the scientific/medical/dietary things we thought we knew (back in the 60s and 70s, for example) turn out to be untrue.

clownbell wrote: ↑

Tue Aug 09, 2022 5:25 pm

Interesting how the scientific/medical/dietary things we thought we knew (back in the 60s and 70s, for example) turn out to be untrue.

but do we think this is true for those of us at the top of the food chain?

Saying some thing at the bottom of the food chain waking often during sleep doesn’t sound so unreasonable.

I don’t know how this relates to the lifespan of a mouse compared to human and memory loss etc.

It’s an interesting concept though. Is it making everyone else rethink their CPAP treatment?

Just kidding

Here are the first word from the study, as published in https://www.nature.com/articles/s41593-022-01102-9

Abstract
Sleep has a complex micro-architecture, encompassing micro-arousals, sleep spindles and transitions between sleep stages. Fragmented sleep impairs memory consolidation, whereas spindle-rich and delta-rich non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep promote it. However, the relationship between micro-arousals and memory-promoting aspects of sleep remains unclear. In this study, we used fiber photometry in mice to examine how release of the arousal mediator norepinephrine (NE) shapes sleep micro-architecture. Here we show that micro-arousals are generated in a periodic pattern during NREM sleep, riding on the peak of locus-coeruleus-generated infraslow oscillations of extracellular NE, whereas descending phases of NE oscillations drive spindles. The amplitude of NE oscillations is crucial for shaping sleep micro-architecture related to memory performance: prolonged descent of NE promotes spindle-enriched intermediate state and REM sleep but also associates with awakenings, whereas shorter NE descents uphold NREM sleep and micro-arousals. Thus, the NE oscillatory amplitude may be a target for improving sleep in sleep disorders.

Leave it to the Danes to question ancient ASSumptions and do research.