Sleep like log?

Reader question:

Please explain “sleep like a log” in this passage: Can’t get to sleep? Perhaps you’re not tired. Run 10 miles like I sometimes do, and, like me, you’ll sleep like a log.

My comments:

The speaker posits that people who cannot get to sleep at night are perhaps not tired enough. If they’re tired enough, such as after running 10 miles, they’ll be able to get to sleep easily. In fact, they’ll be able to sleep like a log.

That is, like a trunk, a trunk of tree that has been cut off.

Dead, in other words, as you can imagine.

To use a similar idiom, they’ll sleep like a dog.

Actually, “sleep like a dog” may be the more familiar expression. And people clearly have derived this idea from observing pet dogs sleeping soundly – and cozily – on the sofa or on the floor.

Dogs get to sleep that way because they play hard, presumably going to sleep only after they’re exhausted.

Pet dogs play hard. Hunting dogs work hard.

In the old days, domesticated dogs worked as hunting dogs, and they spared no energy chasing prey. In fact, hardworking hunting dogs is believed by some to give rise to the expression, “dog tired”, as TheIdioms.com explains:

Dog tired is an old English idiom usually hyphenated to dog-tired. An adjectival phrase meaning to be physically exhausted, it derives from an ancient tale of Alfred the Great, who used to send his sons out with his widespread kennels of hunting dogs. Whichever of his sons, be it Athelbrod or Edwin, were able to catch more of the hounds would gain their father’s right-hand side at the dinner table that evening. These chases would leave them ‘dog-tired’ yet merry at their victory.

Anyways, dogs work hard and, therefore, they sleep hard – I mean, soundly.

Well deserved, too.

This “dog-tired” theory agrees with the opinion of the speaker in our example, who believes if you’re tired enough, you’ll be able to fall sleep the minute your head touches the pillow in bed.

And when you do, in fact, you may be able to sleep like a log.

Or a dog.

Same thing.

Only when you’re dog tired, of course.

Or dead tired, in other words.

All right, no more ado. Let’s read two media examples of “sleep like a log”:

1. Pope Francis says sleeping six hours “like a log” each night is part of his secret for managing job stress.

Italian Catholic TV channel TV2000 asks Francis, in an interview being broadcast Sunday, how he manages to look “never stressed” even while tired and even with his 80th birthday approaching on Dec. 17.

Francis jokingly asked his interviewers if they’re angling for an answer like “a special tea.” Instead, he replied, he’s helped greatly by prayer.

He adds: “Then I sleep well, thanks to the Lord. I sleep like a log,” six hours a day. He figures sound sleep probably boosts his health.

Francis says he has had some spinal column problems, but says they’re resolved. He also paces himself, saying: “I do what I can and nothing more.”

- Pope says sleeping ‘like a log’ helps him handle stress, APNews.com, November 20, 2016.

2. Deep in the bowels of “sleep’s engine room”, Danish researchers have now identified oscillations crucial to memory, suggesting novel targets for improving sleep.

This discovery was made by an international research team headed by sleep experts from the University of Copenhagen. In addition to improving our understanding of sleep, the finding also indicates a need to design novel medicines for treating sleep disorders.

Just has you can be as fresh as a daisy, as fast as lightening or as slow as a snail, you can sleep like a log.

Lots of us will say we “slept like a log” when we’ve had a really good night’s sleep. And then we might add with a grin: ‘I didn’t wake up once.’

The experience of having had a good night’s sleep is genuine – and is usually underpinned by a feeling of having gained energy from the sleep. However, on closer inspection, the claim not to have woken up “a single time” doesn’t wash. And this is one of the key points of a new research article published in Nature Neuroscience, one of the world’s most prestigious neuroscience journals.

The story is complex in many ways, involving the deciphering of existing brain activity using microscopic optic fibres implanted in mouse brains. These optic fibres communicate with genetically engineered receptors capable of measuring the incidence of biochemical substances and lighting up like tiny party lanterns.

And the story also contains ideas for the design of novel medicine for treating sleep disorders.

The article was authored by a team of Danish and Chinese researchers, headed by three sleep experts from the Centre for Translational Neuroscience at the University of Copenhagen: Professor Maiken Nedergaard, Assistant Professor Celia Kjærby and PhD student Mie Andersen who all received funding from the Lundbeck Foundation.

The article describes a previously unknown phenomenon: significant variations in the concentration of the norepinephrine hormone and neurotransmitter in the brains of mammals both regulate sleep patterns and consolidate memory.

One of the consequences of this regulation during the sleep phase is that the brain actually wakes up countless times during the night. The new research article shows that, at times, the brain will wake up once or twice a minute – much more frequently than previously thought.

And by measuring the electrical activity of the brain, the researchers found that the sleeper is usually unaware of this. It is assumed that the sleeper fails to register that they are awake because each awakening is extremely brief, representing the crest of an ongoing, wave-like sleep pattern driven by norepinephrine. There is then a rapid descent from the crest of the wave to a deep valley of sleep. Here, other measurements of the brain’s electrical activity indicate that it is now soundly asleep. As soon as it passes through this valley, the brain heads for the next crest and briefly wakes up again.

The sleep pattern and the dynamic it creates continue in this way – provided, of course, that the sleeper is experiencing non-rapid eye movement (NREM) sleep. Approximately 75-80% of a night’s sleep is NREM sleep when we do not dream.

It is a well-established fact that there is a connection between NREM sleep and memory. Celia Kjærby explains that this type of sleep consolidates in our memory the impressions and information we gather during our waking hours. She and Mie Andersen are the first authors of the scientific article in Nature Neuroscience:

“But until now we’ve lacked information about the details of this consolidation and the role norepinephrine plays in this context. This is where we can contribute new knowledge by demonstrating that norepinephrine also plays an essential role while we sleep.”

Norepinephrine is closely linked to the waking hours of our lives – the hours when we are active – and it is also a so-called stress hormone, released when we experience fear or tension. Therefore, in sleep research circles it has been assumed that norepinephrine is relatively calm when we are asleep – because, otherwise, it would stop us from sleeping. Celia Kjærby says:

“But we were able to prove that this is not the case. And the finding is very exciting because it gives us a better understanding of how NREM sleep helps us store things in our memories.”

- Wake up during the night? Oscillatory sleep states are actually best for your brain, LundbeckFonden.com, July 14, 2022.

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About the author:

Zhang Xin is Trainer at chinadaily.com.cn. He has been with China Daily since 1988, when he graduated from Beijing Foreign Studies University. Write him at: zhangxin@chinadaily.com.cn, or raise a question for potential use in a future column.

（作者：张欣）