Octopuses possess a brain wave that has never been seen before in animals, along with others similar to those found in humans, first-of-their-kind brain recordings reveal. 

The groundbreaking study captured the first ever brain recordings of freely moving octopuses and was performed by implanting electrodes in the animals’ brains and connecting them to data loggers under their skin. The recordings have given scientists the very first inklings into the workings of cephalopod minds. The researchers published their findings March 27 in the journal Cell (opens in new tab).

"Some of these activity patterns have some similarity to activity patterns observed in the mammalian hippocampus, also a memory center," first-author Tamar Gutnick (opens in new tab), a visiting scientist at the University of Naples, told Live Science. "But we also observed unique patterns, 2Hz activity, that were never reported in other animals."

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Octopuses and their close cephalopod relatives, such as squid and cuttlefish, have been a subject of fascination among biologists ever since the third century A.D., when Roman author and naturalist, Claidius Aelianus, noted their "plainly seen" characteristics of "mischief and craft." Octopuses and other cephalopods have long been studied because of their intelligence. Octopuses possess remarkable memories, excel at camouflage; are curious about their surroundings, have been observed using tools to solve problems, and — as the ripples of colors that flash across their skin as they sleep indicate — are even thought to dream.  

However, octopuses’ minds can be difficult to peer into. The creatures’ arms can reach to any part of their boneless bodies, so not only can they easily snatch and detach any invasive tracking object, but there is no obvious place in which to anchor recording devices that can detect brain waves. 

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To get around this, the researchers surgically inserted medical tracking devices into the heads of three captive octopuses, placing lightweight data loggers often used on birds between their eyes before connecting them to electrodes inserted into a region of the octopuses’ brains responsible for learning and memory. The scientists then recorded the octopuses for 12 hours as the creatures slept, groomed themselves and explored their tank.

The recorded brain wave patterns surprised the scientists in a number of ways. First of all, the researchers discovered brain waves that were very similar to those found in the human hippocampus. This hints at convergent neurological evolution — where two separate animals evolve the same trait independently of each other — as humans’ last common ancestor with octopuses was a seafloor-trawling flatworm that lived around 750 million years ago and did not possess anything other than a rudimentary brain. The researchers also found brain waves known for control sleep-wake cycles in other animals.

The researchers also found never-before-seen brain waves in the recordings, which were long-lasting and slow, repeating just twice every second. Scientists aren’t sure what these mysterious brain waves are being used for, and it will take more recordings while octopuses complete set tasks to fully map them, the researchers said.

"Most likely they all require recordings on octopuses that are trained to show certain behaviors, so that we can get several repetitions with similar behavior," Gutnick said. "In vertebrates, this is the key to finding patterns in brain activity that help us to understand how the brain coordinates behavior."