Octopus brainwaves tracked with data-loggers

A day octopus camouflages itself against the coral reef. Image: Keishu Asada

Scientists in Japan have successfully recorded brain activity from freely moving octopuses, a feat made possible by implanting electrodes and a data logger directly into the creatures.

The study is a critical step forward in figuring out how octopuses brains control their behaviour and could provide clues to the common principles needed for intelligence and cognition to occur.

Dr Tamar Gutnick, first author and former postdoctoral researcher at the Okinawa Institute of Science & Technology (OIST), said, “If we want to understand how the brain works, octopuses are the perfect animal to study as a comparison to mammals. They have a large brain, an amazingly unique body and advanced cognitive abilities that have developed completely differently from those of vertebrates.”

“If we want to understand how the brain works, octopuses are the perfect animal to study."

Tamar Gutnick, Okinawa Institute of Science & Technology

Measuring the brainwaves of octopuses has proven a real technical challenge. Unlike vertebrates, octopuses are soft bodied, so they have no skull to anchor the recording equipment onto, to prevent it being removed.

“Octopuses have eight powerful and ultra-flexible arms, which can reach absolutely anywhere on their body,” Dr Gutnick explained. “If we tried to attach wires to them, they would immediately rip them off, so we needed a way of getting the equipment completely out of their reach, by placing it under their skin.”

The researchers settled on using small, lightweight data loggers that were originally designed to track the brain activity of birds during flight. The devices were adapted make them waterproof, but still small enough to easily fit inside the octopuses.

A day octopus with a Shisa, a creature from Okinawan folklore. Image: Michael Kuba

The researchers chose the octopus cyanea species, known as the day octopus, as their model animal, due to its large size. They anaesthetised three octopuses and implanted a logger into a cavity in the muscle wall of each of their bodies.

Scientists then implanted the electrodes into an area of the octopus’ brain called the vertical lobe and median superior frontal lobe, which is the most accessible area. This brain region is believed to be important for visual learning and memory, which are brain processes that Dr Gutnick is particularly interested in understanding.

Once the surgery was complete, the octopuses were returned to their home tank and monitored by video. After five minutes, the octopuses had recovered and spent the following 12 hours sleeping, eating and moving around their tank, as their brain activity was recorded.

The researchers believe that this method of recording brain activity from freely moving octopuses can be used in other octopus species and could help solve questions in many other areas of octopus cognition, including how they learn, socialise and control the movement of their body and arms.

Professor Michael Kuba, who led the project, said, “This is a really pivotal study but it’s just the first step. Octopus are so clever, but right now, we know so little about how their brains work.

"This technique means we now have the ability to peer into their brain while they are doing specific tasks. That’s really exciting and powerful.”

The study involved an international collaboration between researchers in Japan, Italy, Germany, Ukraine and Switzerland.