February 21, 2024

Octopus brains share some striking similarities to our own, and scientists have spent years trying to figure out whether octopuses have dreams.A recent study even claims that eight-armed cephalopods have a physical response during sleep that resembles being attacked by a predator, suggesting that they experience nightmare.

Now, researchers at the Okinawa Institute of Science and Technology (OIST), in collaboration with the University of Washington (UW), have studied the brain activity and patterning behavior of a small shallow-water octopus from Japan. octopus trapand demonstrated that not only are animals asleep during these moments of “active sleep,” but that there are similarities to our own rapid eye movement (REM) sleep.

When octopuses doze off, their “quiet sleep” is interrupted by brief bouts of REM sleep-related frenzy during “active sleep” — their patterns flash brightly, their eyes and arms twitch, their breathing rate increases. will also speed up.

While researchers can’t claim to have proven that animals are dreaming, the REM state in mammals is the sleep stage in which dreaming is most frequent.

“All animals seem to exhibit some form of sleep, even simple ones like jellyfish and fruit flies,” said OIST professor Sam Reiter, the study’s senior author. “But for a long time, we’ve only known that vertebrates cycle between two distinct sleep stages.”

During “quiet sleep,” the octopus brain emits waves that mammals like us see during non-REM sleep, called sleep spindles, which are thought to be involved in the consolidation of memories. The study’s first author, Tomoyuki Mano, made the microscope and found that these sleep spindle-like waves originate in brain regions associated with learning and memory, suggesting that they function very similarly to humans.

“The fact that two phases of sleep evolved independently in distantly related organisms, such as octopuses, whose brain structures are large but completely different from those of vertebrates, suggests that having an active, wake-like phase may be complex. A universal feature of cognition,” said Leenoy Meshulam from the University of Washington.

When the scientists weren’t giving the octopuses ecstasy, they “brushed their skin lightly with a paintbrush”. Interruptions every two to three minutes over a 48-hour period were done to see how sleep deprivation affected these two sleep states. It resulted in a higher rate of active sleep and sooner onset, indicating absolute certainty that this flickering and twitching state was indeed sleep.

“This compensatory behavior establishes that the active phase is an important phase of sleep that octopuses need to function properly,” said Aditi Pophale, an OIST doctoral student and co-first author of the study.

Additionally, high-resolution photography of octopus patterns during active sleep revealed that the animals were the same color and shape as when they were awake. While it’s also possible that octopuses do this to “practice” waking camouflage, or simply to maintain the health of their pigment cells, it could also indicate that the animal is remembering or relearning moments of its conscious time — like a dream state.

“In this sense, while humans can only verbally report what kind of dreams they are having after waking up, octopus skin patterns can serve as a visual readout of brain activity during sleep,” Wright said. “We currently do not know which of these explanations, if any, are correct. We are very interested in investigating further.”

Meanwhile, scientists at OIST and the Max Planck Institute for Brain Research have learned more about cuttlefish, the octopus’ closest relative, and how their ability to color-correct camouflage patterns suggests a higher level of cognitive function and ability. Autonomy over their changes is greater than previously thought.

Cuttlefish are good at using their skin organs and pigment cells to blend into the environment, and the pigment cells contract and relax according to the instructions of the brain neurons to adjust pigmentation.

The stunning head of the common cuttlefish shows off its detailed patterns
The stunning head of the common cuttlefish shows off its detailed patterns

But as Sam Reiter, who also works on octopuses, discovered, it’s the little things that make the difference.

“Previous research has shown that squid have only a limited choice of pattern components that they can use to achieve the best match to their environment,” Wright said. “But our latest study shows that their camouflage response is much more complex and flexible — we just couldn’t detect it because previous methods weren’t as detailed or quantitative.”

Close inspection of the European cuttlefish’s skin using an ultra-high-resolution camera (squid) in the context of a rapid loop, they collected about 200,000 images and analyzed them with some kind of artificial intelligence.

The fascinating results showed that animals cycle patterns and adjust for each individual chromatophore in which they tuned. possibly millionsuntil they settle on an overall look they agree with.

Animals don't use the same color changing path to reach the final pattern
Animals don’t use the same color changing path to reach the final pattern

The scientists observed them “color correct” so that each path to the final pattern is different even when exposed to the same background, suggesting a hitherto unobserved complexity in their behavior.

“Squids often step outside of their target skin patterns, pause, and then come back,” said Theodosia Woo, co-first author of the study at the Max Planck Institute for Brain Research. “In other words, cuttlefish do not simply detect the background. And go directly to the set pattern, instead they are likely to receive constant feedback about their skin pattern and use it to adjust their camouflage.

“Exactly how they receive the feedback—whether they use their eyes, or whether they can feel how much the muscles around each pigment cell contract—we don’t yet know,” she added.

“The next step is to capture neural recordings from the squid’s brain so we can further understand exactly how they control their unique and fascinating skin-patterning abilities,” said study co-first author Xitong Liang, formerly of the Max Planck Institute. explain.

this octopus study and cuttlefish study both published in journals nature.

Watch the video below to see how an octopus changes patterns during REM sleep, and below that, see the cuttlefish’s incredible color-correcting skills as they search for just the right look.

Octopus during active sleep

cuttlefish in disguise

source: Okinawa University of Science and Technology (octopus), Okinawa University of Science and Technology (squid)