The octopus has impressive cognitive abilities and is admired for its intelligence. Despite this reputation, however, we know very little about the workings of its brain, writes New Science.

Deciphering it could provide valuable clues to understanding the most complex nervous systems, including our own. By carefully studying the nervous system of these cephalopod mollusks, an international research team has recorded the brain waves of free-moving individuals for the first time. This is a real technical feat that could lead to a better understanding of how animals' brains drive their incredible intelligence and unusual cognitive abilities.

With eight limbs, three hearts and several brain centers providing it with astonishing intelligence, the octopus is a mysterious and fascinating animal that sometimes eludes our understanding. "They come closest to the study of an intelligent alien on Earth," says Sam Reiter, a researcher in the computational neuroethology department at the Okinawa Institute of Science and Technology (OIST) and an expert on coleoidal cephalopod mollusks. The octopus's nervous system, consisting of 500 million neurons, is as extensive as that of a dog. However, unlike dogs and other vertebrates, the vast majority (more than two-thirds) of octopus neurons are distributed in its limbs and other parts of the body. This giant network of neurons allows it to solve complex cognitive puzzles, have a heightened perception of its environment and merge with it, bait predators, control its eight arms with perfect coordination, etc. A new study led by OIST aims to determine how the octopus controls its movements and behavior and which brain circuits govern this control. Specifically, each tentacle contains more than 200 suction cups, whose movements and contractions are constantly coordinated to sense and potentially capture everything in the animal's environment. In addition, each of these tentacles can twist and bend at will in an almost innumerable number of configurations. The coordination of movements must be done in parallel with the control of the cephalopod's vital and autonomous functions. Controlling all this requires processing a very large amount of information in real time.

Research results have shown that octopus tentacles have both proprioception (the ability to sense where a limb is and how it moves) and the ability to process tactile information. Thus, the animal's nervous system is much more complex than previously thought. The octopus has a soft body, and it is very difficult to attach electrodes in the absence of a skull. In addition, the animal systematically pulls off any object stuck to any part of its body, due to the flexibility of its limbs. As a result, recording electrical activity in the animal's nervous system was, until recently, an impossible task. To be able to attach the recording devices, the researchers decided to implant them under the skin of three Octopus cyanea octopuses. For 12 hours after surgery, they were observed sleeping, eating and moving around. The recording devices were then retrieved and analyzed by synchronizing with the surveillance videos. While observing, the researchers found several distinct patterns of brain activity, some of which were similar in size and shape to those observed in mammals. Surprisingly, slow and very long oscillations were also detected, which had never before been observed in any other animal. As a next step, the researchers intend to observe these electrical oscillations by having the octopus perform specific learning tasks.