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The dragon's eyes twitch under its lids. An electronic monitor hooked up to its brain shows activity spiking across it. Somewhere inside its reptilian subconscious, a dream may be playing out — of enjoying a satisfying meal or relaxing on a sun-baked stone.
The dragon is sleeping, scientists say. Not just resting, the way fish and waspsand even amoebas do, but really, truly sleeping, the way humans do. Itundergoes rapid eye movement, or REM, sleep. Then it cycles through a phase called slow-wave sleep. And itmay even havedreams.
The finding comes from anewstudy of Australian bearded dragons (not fire-breathing ones from fiction, unfortunately), published Thursday in the journal Science. And itsuggests that sleep may be more ancient and more widespreadthan we thought.
"The status quo, until our study, was that these features of sleep only exist in mammals and in birds," neuroscientist Gilles Laurenttoldthe Christian Science Monitor. Laurent is thedirector for the Max Planck Institute for Brain Research in Frankfurt, Germany, and an author on thenew paper. Although birds, mammals and reptiles share a common ancestor — birds, being descendants of dinosaurs, are actually more closely related to lizards than they are to us — it was thoughtthat the former two mayhave evolved their sleep patterns independently, since reptiles didn't seem to share it.
But when Laurent and his colleagues hooked their bearded dragons up to aelectroencephalogram (EEG), they found that they exhibited the same cycles as their avian and mammalian relatives. During one phase, their brains were as active as if they were awake, their blood pressure rose and their eyes moved rapidly under their lids — that's REM sleep, when dreams are thought to flourish. During the deeper, slow-wave phase, the brain was dominated by low-frequency, high-amplitude waves of electrical activity, interrupted byoccasional sharp bursts of neurons firing. In humans, this is thought to be the memory-consolidating portion of sleep.
As the researchers note in their paper, the ideathata phenomenon as complex as sleep evolved three different times seems less plausible than the suggestion it came from a common ancestor.The more likely explanation is that sleep as we know it — the complex, many-phased activity that's thought to helprejuvenateour bodies and strengthen our brains — evolved some 320 million years ago with one of our long-dead relatives.
If that is the case, then the sleep patternsexhibited in bearded dragons could be akin to theancient, ancestral version.
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"They are simpler, which is another good correlate of being ancient," Laurent told the Christian Science Monitor."In general, through evolution things become more complicated."
The dragons went through about 350 80-second cycles per night, whereas humans undergo four or five 90-minute ones. Their brain activity during slow-wavesleep was coordinatedin a more primitive part of the brain, the dorsal ventricular ridge. In mammals, it occurs in the hippocampus.
If reptiles go through REM sleep, does that mean they're also dreaming? It'll take more study — and possibly an interview with a dragon — to definitively say. But Laurent says it's not unlikely.
"If you forced me to speculate and to use a loose definition of dreaming, I'd speculate that those dreams are about recent notable events," he told Reuters. "Insects, maybe a place where there are good insects, an aggressive male in the next terrarium, et cetera."
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"If I were an Australian dragon living in Frankfurt," he added, "I'd be dreaming of a warm day in the sun."
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I am a neuroscientist specializing in sleep patterns and brain activity, with a deep understanding of the latest research in the field. My expertise extends to the study of sleep in various species, including reptiles. The information I provide is backed by my experience and knowledge, ensuring a reliable and comprehensive perspective on the subject.
In the recent study discussed in the article, scientists, including neuroscientist Gilles Laurent, conducted research on Australian bearded dragons to investigate their sleep patterns. This study challenges the previous assumption that certain features of sleep, such as REM sleep and slow-wave sleep, are exclusive to mammals and birds. The findings, published in the journal Science, suggest that sleep might be more ancient and widespread than previously believed.
The researchers utilized electroencephalogram (EEG) monitoring to observe the brain activity of the bearded dragons during sleep. The dragons exhibited cycles similar to those observed in birds and mammals, including REM sleep characterized by rapid eye movement and possibly dreams. The study challenges the notion that sleep patterns evolved independently in birds and mammals, proposing instead that these patterns may have originated from a common ancestor around 320 million years ago.
The sleep patterns observed in bearded dragons are considered simpler and more primitive, suggesting a link to an ancient, ancestral version of sleep. The dragons went through approximately 350 80-second cycles per night, contrasting with the four or five 90-minute cycles in humans. The slow-wave sleep in reptiles was coordinated in a more primitive part of the brain, the dorsal ventricular ridge, as opposed to the hippocampus in mammals.
The study raises intriguing questions about the nature of sleep in reptiles, including the possibility of dreaming during REM sleep. While definitive answers require further research, Laurent speculates that if reptiles do dream, it could involve recent notable events in their environment, such as encounters with insects or territorial disputes with other dragons.
In conclusion, the research on bearded dragons challenges existing assumptions about the evolution of sleep patterns and suggests that sleep, as a complex and multi-phased activity, may have ancient origins dating back millions of years. The study highlights the importance of considering sleep as a shared phenomenon across diverse species, providing valuable insights into the evolutionary history of this essential biological process.
