Because of how intelligent their tentacles are and how similar they are to us, octopuses are intriguing to study. But they share more with us than just that. A recent Japanese-American research suggests that these aquatic critters have the ability to dream. 29 nocturnal Octopus laqueus were studied by scientists from the Okinawa Institute of Science and Technology (OIST) and the University of Washington on their brain activity and skin color variations. They discovered that the octopuses assumed a sleeping-like posture and closed their eyes throughout the day. These animals also experienced quick changes in skin tone that lasted for approximately a minute, variations in respiration rate, and variations in body and eye movements.
Due on their data, the researchers were able to conclude that octopuses experience two distinct phases of sleep: silent sleep and active sleep. According to the study team’s work, which was just published in the journal Nature, the octopus’s body begins to constrict in the later stage, and its skin’s structure and pattern rapidly change.
The researchers put the octopuses through a variety of external stimuli to see whether they were indeed in the active sleep stage in order to test this theory. They focused on tapping the tanks where the animals were resting to see how they responded. When they were awake, or when they were in a calm or active sleep period, the marine animals responded differently. The study team also discovered that after two days of sleep deprivation, the octopuses entered the active sleep state sooner and more often. This discovery raises the possibility of a homeostatic mechanism, which is one of the important prerequisites for sleep.
experiencing the past again
Additionally, octopus neural activity recording probes discovered sleep-like spindle-like brain waves. A group of waves known as sleep spindles are considered to safeguard sleep by obstructing sensory information. Even in humans, the precise role of these spindles is still unknown, although researchers think they play a role in memory consolidation. The fact that these waves are seen in octopuses’ learning and memory-related brain areas suggests that they may serve a similar purpose to those in humans, according to biologists.
The modifications in octopus skin patterns that researchers have seen may be explained by these sleep spindles. Indeed, hundreds of coloured cells called chromatophores enable octopuses to rapidly and in a variety of ways alter the texture and look of their epidermis in order to mimic their surroundings. They can conceal from prospective predators thanks to this protection mechanism.
The researchers noticed that octopuses alternate the same skin patterns throughout the active sleep cycle. This phenomena could be accounted for by the fact that animals use their sleep to hone their camouflage abilities or merely to check that their chromatophores are functioning correctly. Another theory, however, suggests that octopuses could be remembering and learning from earlier events, such as when they were hunting or hiding from a predator, by reactivating the skin pattern connected to those memories. To put it another way, they may be dreaming.
According to Dr. Sam Reiter, associate professor and head of the Computational Neuroethology Unit at OIST, “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,” he was quoted in a news release. We don’t now know which of these hypotheses, if any, may be accurate, he said. We are extremely eager to look into this further.