Nine brains, blue blood, instant camouflage: it’s no surprise that octopuses pique our interest and imagination. Science fiction creators in particular have been inspired by these tentacled creatures.
An octopus’s remarkable intelligence also makes it a unique subject for marine biologists and neuroscientists. Research has shown that the octopus’ brain power allows it to unscrew a jar or navigate a maze. But, like many children, the octopus also develops a mischievous tendency to push the boundaries of behavior. Several aquariums have found octopuses memorizing watch schedules to sneak into nearby tanks to steal fish; meanwhile, marine biologists have discovered that wild octopuses will strike fish… for no apparent reason.
According to dr. Jennifer Maher, a professor at the University of Lethbridge in Canada, “are several [different] types of learning [for octopuses]: cognitive tasks such as tool use, memory of complex operations for future reference, and observational learning.”
How does the peculiar structure of the octopus’s brain make all this complex behavior possible? No one had successfully studied the brain waves of wild or free-moving octopuses until a new study by researchers from the University of Naples Federico II in Italy and the Okinawa Institute of Science and Technology (OIST) in Japan, among others. In their Current Biology paper, the researchers followed and tracked three captive but free-moving octopuses, analyzing their brain waves for the first time. Using recording electrodes, the researchers found a type of brain wave that had never been seen before, along with brain waves that may be similar to some seen in human brains, possibly providing hints about the evolution of intelligence.
Cunning cephalopods
Our current understanding of octopus intelligence may seem incredible. In 2011, researchers discovered that each arm of the cephalopods has its own “brain.” Using a transparent maze with food inside, kept outside the tank, the researchers forced the octopus to navigate the maze using only its arm, even though it could see where the food was. The octopus could not rely on chemical signals processed by its brain to find the food, as it usually does in the ocean, forcing the arm’s individual “brain” or neuron bundle to find the food itself by localizing the signals. process . Each octopus arm is believed to have about 10,000 neurons dedicated to sensing its environment.
Other research shows that apart from some insects, octopuses are the only invertebrates that use tools. They will compress grenades around their bodies as a kind of proto-armor and camouflage against predators.
Octopuses can also mimic human movements by walking bipedally, lifting six of their legs like a skirt and gliding across the ocean floor. However, that seems to be one of the few similarities between these cephalopods and humans, as evolution has separated us for many millions of years.
“The huge difference between octopuses and us stems from more than 550 million years of independent evolution,” explains Dr. Michael Kuba, the OIST project leader for the 2023 octopus brainwave study, who now works at the University of Naples. “Our closest common ancestor probably resembled a flatworm.” Still, Kuba and his team are looking at the few similarities to learn more about the evolution of mental abilities.
Wiring the brain of an octopus
Reading the brain of an octopus is not an easy task. For starters, the animals are nearly impossible to track in the wild. “Octopuses are hard to see, plus they often run out of water in tide pools,” Maher added. “Only some of them get used to humans, and many species are nocturnal.”
To avoid these complications, many researchers are turning to captive octopuses to study their brains. But even this can be a challenge. “Since the octopuses have eight ultra-flexible arms that can reach any part of their body and have a soft body without a skull to anchor the recording equipment, the challenge of this project was to realize a new equipment that was out of reach,” said Dr. Anna Di Cosmo, a professor at the University of Naples and a researcher involved in the 2023 study.
Range is important because the animal often removes or plays with the recording equipment. Kuba, Di Cosmo and others decided to take a new approach by implanting their recording equipment inside the brain of the octopus, far out of reach.
An octopus lobotomy
“We have developed a new technical solution capable of recording signals underwater, using small and lightweight data loggers, originally used to monitor the brain activity of birds in flight,” added Di Cosmo. These repurposed lumberjacks were carefully placed in the upper heads of three captive tropical octopuses, just between their eyes. “The electrodes were implanted in an area of the octopus brain called the vertical lobe and median superior frontal lobe,” Di Cosmo explained, “which is the most accessible area and thought to be important to control learning and memory processes .”
The octopuses were sedated during their operations. They spent the next 12 hours recovering, followed in their tanks, as they were the first octopuses to be studied in real time. “We also filmed them with a sensitive camera as they swam, slept and explored their surroundings,” Kuba added. While the researchers didn’t get the octopuses to engage in brain-teasing activities during the next 12 hours of study, they did find interesting brain activity in their subjects.
When the team first looked at the brain waves of an octopus, the results were shocking. As Di Cosmo explained, these features were “protracted, slow oscillations not previously described.” As far as we know, these signatures appear to be unique to the octopuses.
Because the researchers didn’t test the octopuses while recording, they couldn’t link these unique brain waves to a specific activity, leaving that question to be answered by a future experiment.
