If you've ever wondered if octopuses dream, science has a stunning answer. When these eight-armed masters of camouflage fall asleep, they don't just fall into a quiet sleep. Instead, they occasionally have brief episodes in which their arms twitch, their breathing quickens, and their skin fluctuates with bright, changing colors.
According to a study published in NatureThese dazzling sleep displays aren't just for show. They may actually discover that octopuses experience a form of dream-like sleep remarkably similar to our own.
Read more: Curious traits of the octopus: how do they understand the world?
How scientists studied the brain of a sleeping octopus
To figure out what really happened during these dramatic bouts of sleep, scientists first needed to confirm that the octopuses were actually sleeping. To do this, they gently nudged them during periods of restful and active sleep and found that the octopuses required more stimulation to respond compared to when they were awake. This lack of response was confirmed as a sign of a real dream.
During restful sleep, the Laceus octopus appears white and motionless. This quiet sleep is interspersed with bursts of sleep that exhibit wake-like activity (active sleep) approximately every hour.
(Image credit: Keishu Asada (OIST))
After confirming sleep status, the research team began tracking octopus brain activity during wakefulness and sleep. During a phase known as restful sleep, the team observed neural activity reminiscent of mammalian “sleep spindles,” a brain wave pattern observed in humans during slow-wave sleep. Although the function of sleep spindles remains a mystery even in humans, many scientists suspect that they help consolidate memories. Using a high-resolution microscope, the researchers found that these spindle waves occur in areas of the brain associated with learning and memory in octopuses.
However, everything changed about once an hour. Each octopus entered about a minute-long burst of activity when its neural patterns suddenly matched what the team had seen when the animals were awake—patterns reminiscent of human REM sleep.
“The fact that dual-stage sleep has independently evolved in distantly related creatures such as octopuses, which have large but quite distinct brain structures from vertebrates, suggests that the presence of an active waking stage may be a general feature of complex cognition,” explained Linoy Mechoulam, a statistical physicist at the University of Washington, in her paper. press release.
Do you really dream about octopuses?
One of the most alien aspects of an octopus is its skin. Octopuses control an amazing collection pigmented skin cells which create striking patterns used for camouflage and communication. To see how these patterns manifested themselves during sleep, the research team filmed the octopuses in ultra-high resolution 8K.
“By filming at such high resolution, we can see how each individual pigmented cell behaves to create the overall skin pattern,” Mechoulam said. “This could help us create simple models of skin patterns to understand general principles of behavior during wakefulness and sleep.”
While reviewing the footage, the research team was surprised by what they found. During active sleep, octopuses change the same skin patterns as when they are awake, suggesting that they may have dreams that influence their skin color to change while they sleep.
Why do you dream about octopuses?
One explanation for this behavior is practical: perhaps they are rehearsing camouflage using a kind of muscle memory. Another explanation suggests that changes in skin patterns during sleep could be a sign that octopuses are dreaming. In this state, the octopus may be reliving actual events from its day, triggering skin patterns associated with memories of evading a predator or pursuing prey.
“In this sense, although humans can only verbally report what dreams they have had after they wake up, octopuses' skin patterns serve as a visual indicator of their brain activity during sleep,” said senior author Sam Reiter.
The results show that complex REM sleep sleep phaseevolved in a surprising way and may be characteristic not only of mammals.
Read more: Dogs have dreams, and they most likely have to do with their toys, food, and you.
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