How Smart Is an Octopus? Marine Mollusk Has the Largest Brain-to-Body Ratio Among Invertebrates

A new study recorded how an octopus' mind works through electrodes implanted into their brains and data loggers that could record up to 12 hours of brain activity. The study of octopuses is very interesting because they are highly intelligent.

Octopus Are Highly Intelligent

The eight-limbed marine mollusk is reportedly the perfect animal to study compared to mammals because they are highly intelligent.

Octopus researcher Tamar Gutnick of the Okinawa Institute of Science and Technology in Japan and the University of Naples Federico II in Italy said octopuses have large brains, unique bodies, and advanced cognitive abilities, which are completely different from vertebrates, Science Alert reported.

They are also highly intelligent and extremely curious. Plus, they are very mobile and are equipped with manipulation and reach skills that are far better than other creatures in Kingdom Animalia.

According to Gizmodo, they are among the few animals to use tools to further their goals. They were observed using coconut shells as their shelters.

An octopus has eight arms, and each arm has its own mini-brain, according to Natural History Museum. Thanks to this, they can complete tasks with their arms more quickly.

Aside from having "mini-brains" in their arms, octopuses' brain-to-body ratio is the largest of any invertebrate and many vertebrates, not including mammals.

They have about as many neurons as a dog. The common octopus, Octopus vulgaris, has around 500 million.

They have demonstrated their intelligence in a number of ways, according to Jon Ablett, curator of the Museum's cephalopod collection, including solving mazes and completing tricky tasks to get food rewards. They are also skilled in getting themselves in an out of a container.

Jon also shared one of its mischievous abilities. He recounted an incident when all fish were missing from a tank. They put on a little video camera to see what happened.

They saw one of the octopuses getting out of its tank and eating the fish. Then, it closed the lid and went back to its own tank without leaving any trace of evidence.

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Octopus Brain Recording Research

According to the researchers, non-invasive equipment that sticks outside the body, like an electrode cap, wouldn't work. Gutnick said if they tried to attack wires, the octopus would only rip it off. So, they needed to get the equipment under its skin to make it completely out of its reach.

The researchers used electrodes and data loggers designed to record the brain activity of free-flying birds. The device is often protected by a waterproof casing of hard plastic and is unsuitable for implantation. So, the researchers developed a streamlined casing of plastic tubing.

They chose three octopuses of the species Octopus cyanea, also known as the big blue octopus. They decided on the said species because they are large with a cavity within the mantle - the central part of its body - where they could place the data logger.

The scientists anesthetized the octopuses directly into their vertical and median superior frontal lobes. The electrodes were connected to the data loggers tucked into the octopus' mantle.

Each data logger had a batter that could record up to 12 hours of brain activity. Researchers placed the octopuses in their tanks and allowed them to go about their usual activities, with their brain activity being recorded.

A video camera was also set up to record what they were doing, so researchers could compare the brain activity to the behavior of each octopus.

When the recording was done, they euthanized the octopuses and retrieved the data loggers. They noticed long-lasting brain activity patterns, including some similar to mammals. However, some patterns are unlike anything in the scientific literature.

Also, some patterns could not be associated with any behaviors seen in the videos. The electrodes were reportedly attached to the brain region linked to learning and memory, so the octopuses in the experiment were not required to perform any learning or memory. However, it could be the focus of future experiments.

Zoologist Michael Kuba, formerly of OIST and now at the University of Naples Federico II, said the study was pivotal, but it's only the first step, suggesting that there's more to learn.

He added that octopuses are intelligent, but little is known about their brains. The study only confirms that we can now peek into their brain while performing their usual activity or specific tasks. He said it's exciting and powerful.

The results of the study were published in Current Biology.