Reptiles And Rem Sleep: What's The Connection?

Do reptiles experience REM sleep? This question has puzzled scientists for years, with some studies suggesting that reptiles do experience a REM sleep-like state, while others have failed to reach a consensus. However, recent research involving Australian bearded dragons has provided new insights into this topic.

Bearded dragons exhibit a period of behavioural sleep characterised by slow-wave activity and rapid eye movements, similar to the REM sleep observed in mammals and birds. These findings suggest that reptiles may indeed experience a form of REM sleep, challenging the previous assumption that only homeothermic species exhibit this sleep stage.

The discovery of REM sleep in reptiles has significant implications for our understanding of sleep evolution. It suggests that REM sleep may have evolved earlier than previously thought, dating back to the common evolutionary ancestors of reptiles, birds, and mammals.

Further research is needed to confirm these findings and fully understand the evolution and functions of sleep across different species.

Reptiles may or may not dream during REM sleep

REM sleep was initially discovered in mammals and was later found in birds. However, the existence of REM sleep in reptiles has been a subject of debate for decades. Some studies on lizards have reported the presence of two sleep states, suggesting the existence of a REM sleep state. On the other hand, other studies on turtles and crocodilians have yielded conflicting results, with some indicating the presence of two sleep states while others disagreeing.

The challenge in determining the presence of REM sleep in reptiles lies in the differences in their neuroanatomy and physiology compared to mammals and birds. Reptiles may exhibit certain behaviours and brain activities that resemble REM sleep, but it is unclear if these are truly equivalent to the REM sleep seen in mammals and birds.

Recent studies using modern methods and technologies have provided new insights. Research on Australian bearded dragons, a type of lizard, has revealed the presence of two distinct sleep states. One state is characterised by slow-wave activity, while the other exhibits wake-like brain activity and rapid eye movements, resembling REM sleep. However, the absence of clear muscle atonia and twitches in these lizards has led to ongoing debates about whether these periods are truly REM sleep or brief awakenings from sleep.

While the existence of REM sleep in reptiles is still not conclusively proven, these findings suggest that REM sleep may have evolved earlier than previously thought. The discovery of REM sleep in reptiles could provide valuable insights into the evolution of sleep and its functions, as well as a better understanding of the common and essential features of vertebrate brain function.

REM sleep in reptiles is linked to the evolution of sleep

REM sleep in reptiles has been linked to the evolution of sleep. Research suggests that the discovery of REM sleep in reptiles indicates that REM sleep is much older than previously thought. Reptiles share a common ancestor with mammals and birds, and the presence of REM sleep in all three groups suggests that REM sleep emerged far earlier than suspected.

REM sleep was initially described in mammals and later found in birds. For years, it was thought that only homeothermic species experienced REM sleep. However, recent studies in lizards have challenged this assumption. Research involving Australian bearded dragons has documented, for the first time, that reptiles experience REM sleep and slow-wave sleep.

The discovery of REM sleep in reptiles has significant implications for understanding the function of REM sleep. It suggests that REM sleep is not correlated with the active lifestyle of homeotherms and may be much older than expected. Further comparative studies on how animals sleep will help reveal the origin of REM sleep.

The presence of REM sleep in reptiles, mammals, and birds indicates that this sleep stage may have evolved at least as far back as the common ancestor of these groups, which lived about 300-320 million years ago. This discovery provides valuable insights into the evolution of sleep and the potential functions of REM sleep across different species.

Reptiles may have two distinct sleep states

Research on Australian bearded dragons, a type of lizard, revealed the presence of two sleep states: one characterised by slow-wave activity and the other by REM sleep. This finding was further supported by studies on two other lizard species, the Argentine tegu and the green iguana. However, the expression of these sleep states differed between the species, and some characteristics of mammalian REM sleep were not observed in the lizards. For example, clear muscle atonia, a hallmark of mammalian REM sleep, was not detected in the lizards.

The presence of two sleep states in reptiles suggests that REM sleep may have a more complex evolution than previously thought. It also raises questions about the functions and significance of REM sleep in different species. Further research is needed to understand the evolution and purpose of sleep across various animal groups.

The presence of REM sleep in reptiles is still a mystery

The presence of REM sleep in reptiles is a topic of ongoing scientific investigation. While some studies have observed REM sleep in reptiles, the evidence is inconclusive, and the interpretation of results is subject to debate.

REM sleep, or Rapid Eye Movement sleep, is characterised by rapid eye movements, brain activity similar to a waking state, muscle atonia, and other physiological changes. It is typically followed by slow-wave sleep, which is characterised by slow brainwaves and little dreaming. These sleep stages are thought to play a role in memory consolidation and other functions.

Historically, REM sleep was believed to be unique to homeothermic species, namely mammals and birds, and absent in reptiles. However, recent studies have challenged this assumption, suggesting that REM sleep may be present in non-mammalian and non-avian species, including reptiles.

Research involving Australian bearded dragons has provided some of the most compelling evidence for the existence of REM sleep in reptiles. Bearded dragons exhibit two distinct sleep states, with one state characterised by high-amplitude sharp waves and the other by beta waves and dominant oscillations. These sleep states bear some resemblance to mammalian REM and non-REM sleep, respectively. Additionally, the presence of eye movements and the suppression of the second sleep state by fluoxetine, a drug that suppresses REM sleep in mammals, further support the idea that reptiles may experience REM sleep.

However, the interpretation of these findings is not without controversy. Some scientists argue that the criteria used to define REM sleep in mammals may not be directly applicable to reptiles due to differences in neuroanatomy, metabolism, and lifestyle. The absence of clear muscle atonia and twitches during the putative REM sleep state in reptiles has also been noted, raising questions about the validity of the findings.

Furthermore, the function of REM sleep remains unknown, and its presence or absence in reptiles has crucial implications for understanding its purpose. If REM sleep is indeed present in reptiles, it suggests that it evolved earlier than previously thought and is not correlated with warm-bloodedness. On the other hand, if REM sleep is absent in reptiles, it could indicate that it is linked to specific characteristics of warm-blooded species.

In conclusion, while there is emerging evidence for the presence of REM sleep in reptiles, particularly in Australian bearded dragons, the interpretation of these findings is complex and subject to ongoing debate. Further comparative studies examining the similarities and differences in sleep states across different species are needed to fully understand the evolution and function of REM sleep.

The discovery of REM sleep in reptiles

Early Studies

The discovery of REM sleep in humans and cats in the 1950s was based on the observation of rapid eye movements during sleep. This observation led to the conclusion that REM sleep was characterised by rapid eye movements, increased brain activity, muscle atonia, and other physiological changes.

Early studies on reptiles, conducted mostly before the 1980s, yielded mixed results. Some studies reported the presence of two distinct sleep states in reptiles, suggesting the existence of REM sleep. However, the majority of these studies were unable to provide conclusive evidence due to various limitations, such as small sample sizes and differences in recording techniques.

Recent Advances

In the last decade, advancements in technology have allowed for more precise measurements of brain activity during sleep in reptiles. Two key studies, published in 2016 and 2018, provided strong evidence for the existence of two distinct sleep states in reptiles, similar to the REM and non-REM sleep observed in mammals and birds.

The 2016 study, conducted by Shein-Idelson et al., focused on the Australian bearded dragon (*Pogona vitticeps*). They found that these lizards exhibited two distinct sleep states, with one state characterised by high-amplitude sharp waves in the dorsal ventricular ridge (DVR) of the brain, and the other state showing desynchronised brain activity similar to wakefulness.

The 2018 study, led by Libourel et al., replicated the findings in the bearded dragon and also examined a different lizard species, the Argentine tegu (*Salvator merianae*). They found that both species exhibited two sleep states, with the second state being characterised by beta waves and dominant oscillations in the DVR.

Ongoing Questions

While the recent studies provide strong evidence for the existence of REM sleep in reptiles, there are still some questions and disagreements regarding the interpretation of the findings. For example, the exact nature of the two sleep states in reptiles and their homology to mammalian and avian REM sleep is still a subject of debate.

Additionally, the function of REM sleep in reptiles remains unclear. While it has been proposed that REM sleep plays a role in memory consolidation and brain maturation in mammals, it is not yet known if these functions are conserved in reptiles.

In conclusion, while the discovery of REM sleep in reptiles is a significant advancement in our understanding of sleep across species, further research is needed to fully elucidate the nature and function of this sleep state in reptiles.

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