The similarity is striking. They also go through two phases of sleep. A quiet one and an active one, similar to the REM phase. That’s right: octopuses dream like humans.
The brain activity and skin pattern of octopuses during this active sleep period was examined. It closely resembles the neuronal activity and skin pattern observed when they are awake. In mammals it happens in a similar way. This provides fascinating insights into the origin and function of sleep.
REM and non-REM
“All animals seem to show some form of sleep. Even simple animals such as jellyfish and fruit flies. Only vertebrates were thought to cycle between two different sleep phases,” the study explains. “This may be a general feature of complex cognition.”
The scientists performed multiple tests to trigger the responses. For example, they prevented or interrupted sleep. This caused the octopuses to enter active sleep earlier and more often when sleeping. “The active sleep phase is essential for octopuses to function properly.” During quiet sleep, brain waves similar to non-REM sleep appeared in mammalian brains. They are called sleep spindles, and they are believed to help consolidate memories. They are produced in regions of the octopus brain related to learning and memory.
When awake, octopuses control thousands of tiny pigmented cells in their skin. They create a wide range of different skin patterns to camouflage themselves in different environments. During active sleep, octopuses changed cyclically through these same skin patterns.
An intriguing idea is that octopuses could be reliving and learning from their waking experiences. For example, hunting or hiding from a predator. That would reactivate the skin pattern associated with each experience. In other words, they could be doing something akin to dreaming.
“Humans can only verbally report the type of dreams they have had once awake. The skin pattern of octopuses acts differently. It’s like a visual readout of their brain activity during sleep,” they explain.
Yes, octopuses dream like humans. Later, technology may be able to transform the electrical impulses in their brains into images. And perhaps we will discover that, from time to time, they dream of humans.