Octopuses may have nightmares

Study of single cephalopod suggests the animals may have narrative dreams

19 MAY 2023

BY CHRISTIE WILCOX

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SUSAN AIDE/WIKIMEDIA COMMONS (CC BY 4.0)

Octopuses may have vivid, narrative dreams—some of which are terrifying—according to a study posted this month on the preprint server bioRxiv. Scientists describe what appeared to be four filmed instances of nightmares in a Brazilian reef octopus (Octopus insularis) named Costello, during which the sleeping animal exhibited bizarre behaviors including abrupt color changes, erratic movements, expelling water from its siphon, and even inking. Although limited conclusions can be drawn from one individual, the researchers noted that the actions are similar to natural stress and antipredator behaviors in this species and therefore could be physical manifestations of frightening dreams. Costello’s life before the lab certainly could have provided nightmare fuel, a study author tells New Scientist. The octopus lost an arm to a predator before he was rescued and taken into captivity. If indeed the episodes were nightmares, that would suggest narrative dreaming independently evolved in cephalopods, and further research on the phenomenon could provide unique insights into the neuroscience of dreams.

See: https://www.science.org/content/article/octopuses-may-have-nightmares

Scientists caught a napping octopus changing its colours on tape, leading them to believe that the animal was camouflaging itself to the environments in its dream. Considering how octopuses have a brain-to-body ratio similar to that of mammals, and many primate and non-primate mammals are known to experience dreams and nightmares, this wasn’t very surprising. However, the prospect of the highly intelligent and problem solving octopuses having complex dreams was exciting. Now, footage of a male Brazilian reef octopus named Costello falling sound asleep has surfaced in the scientific community leading to many neurological questions.
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I like to think of octopuses 🐙 as these imaginative beings, exploring the depths of their underwater dreams. Maybe they dream about hunting for food, solving puzzles, or even encountering other curious creatures like themselves. Who knows what adventures they embark on in their slumber? Maybe one day we'll uncover more about their underwater dreamscape and understand what makes them tick during their slumber.
 

Octopus may experience REM sleep, and dream, much like we do​

By Bronwyn Thompson
June 29, 2023

Scientists have spent years trying to work out if octopuses, whose brains have some remarkable similarities to our own, have dreams. A recent study even purported that the eight-armed cephalopods can have physical reactions in their sleep, akin to being attacked by a predator, suggesting they experience nightmares.

Now, researchers from the Okinawa Institute of Science and Technology (OIST), in collaboration with the University of Washington (UW), have examined the brain activity and patterning behavior of a small, shallow-water octopus from Japan, Octopus laqueus, and confirmed that not only is the animal asleep during these ‘active sleep’ moments, but it shares similarities to our own rapid eye movement (REM) slumber.

When octopuses snooze, their ‘quiet sleep’ is interrupted with short periods of frenzied REM-adjacent behavior in ‘active sleep’ – their patterning flashes brightly, their eyes and arms twitch and their breathing rate quickens.

While the researchers can’t claim to have proved the animals are dreaming, the REM state in mammals is the stage of sleep in which dreams most frequently occur.

“All animals seem to show some form of sleep, even simple animals like jellyfish and fruit flies,” said Sam Reiter, senior author of the study and professor at OIST. “But for a long time, only vertebrates were known to cycle between two different sleep stages.”

During ‘quiet sleep,' the octopus brain emitted the kind of waveforms seen during non-REM sleep in mammals like us, known as sleep spindles, which are thought to be related to consolidating memories. With a microscope built by the study’s first author, Tomoyuki Mano, these sleep-spindle-like waves were found to be originating in the brain region associated with learning and memory, hinting that they could function much like they do in humans.

“The fact that two-stage sleep has independently evolved in distantly related creatures, like octopuses, which have large but completely different brain structures from vertebrates, suggests that possessing an active, wake-like stage may be a general feature of complex cognition,” said Leenoy Meshulam from UW.

And when scientists aren’t giving octopuses ecstasy, they’re “gently brushing their skin with a paintbrush.” This interruption every two to three minutes over a period of 48 hours was to see what effect sleep deprivation would have on those two sleep states. It resulted in a greater rate of active sleep, which was initiated more rapidly, revealing that with absolute certainty this state of flashing and twitching was indeed sleep.

“This compensatory behavior nails down the active stage as being an essential stage of sleep that is needed for octopuses to properly function,” said Aditi Pophale, co-first author of the study and PhD student at OIST.

Furthermore, high-definition filming of the octopus patterning while in active sleep showed that the animals cycled through the same colors and shapes as when awake. While it’s also likely the octopus does this for ‘practice’ in camouflage for when it’s awake, or to simply maintain the health of the pigment cells, it could also indicate the animal is remembering or re-learning moments of its conscious periods – like a dream state.

“In this sense, while humans can verbally report what kind of dreams they had only once they wake, the octopuses’ skin pattern acts as a visual readout of their brain activity during sleep,” said Reiter. “We currently don’t know which of these explanations, if any, could be correct. We are very interested in investigating further.”

Meanwhile, also out of OIST, along with the Max Planck Institute for Brain Research, scientists have discovered more about the octopus’ cousins, the cuttlefish, and how their ability to color-correct their camouflaging patterns indicates a much greater level of cognitive function and autonomy over their changes than previously thought.

Cuttlefish are masters at blending into their environment by use of their skin organs, chromatophores, which contract and relax as directed by neurons in the brain to adjust pigmentation.

But as Sam Reiter, who also worked on the octopus study, found out, the devil is in the detail.

“Prior research suggested that cuttlefish only had a limited selection of pattern components that they would use to achieve the best match against the environment,” Reiter said. “But our latest research has shown that their camouflaging response is much more complicated and flexible – we just hadn’t been able to detect it as previous approaches were not as detailed or quantitative.”

Using ultra-high-resolution cameras to closely examine the skin of the European cuttlefish (Sepia officinalis) against rapidly cycling backgrounds, they collected around 200,000 images that were analyzed by a type of AI.

The fascinating results showed that the animal would cycle through patterns, adjusting it with each individual chromatophore, of which they potentially have millions of, until they settled on an overall look they approved of.

The scientists observed them ‘color-correcting,’ and each path to the final pattern was different, even when exposed to the same background, suggesting a complexity in their behavior that hasn’t been observed until now.

“The cuttlefish would often overshoot their target skin pattern, pause, and then come back,” said Theodosia Woo, joint first author of the study from the Max Planck Institute for Brain Research. “In other words, cuttlefish don’t simply detect the background and go straight to a set pattern, instead, it is likely that they continuously receive feedback about their skin pattern and use it to adjust their camouflage.

“Exactly how they receive that feedback – whether they use their eyes, or whether they have a sense of how contracted the muscles around each chromatophore are – we don’t yet know,” she added.

“The next step is to capture neural recordings from cuttlefish brains, so we can further understand exactly how they control their unique and fascinating skin patterning abilities,” said Xitong Liang, joint first author of the study and formerly at the Max Planck Institute.

The octopus study and the cuttlefish study were both published in the journal Nature.

Sources: Okinawa Institute of Science and Technology (octopus), Okinawa Institute of Science and Technology (cuttlefish).

See: https://newatlas.com/biology/octopus-dream-rem-sleep-cuttlefish/

Costello, a male Brazilian reef octopus may even have had nightmares about a predator removing two and a half of his arms. That’s the theory posed by researchers in a paper published last week on the preprint server bioRxiv. In the study, which has not yet been peer-reviewed, the team describes Costello’s bizarre behaviors while sleeping, which suggest octopuses can have vivid dreams.
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