Octopuses are considered one of the most intelligent invertebrates. Their sensory and motor activities are autonomous and coordinated by a complex central nervous system. The octopus brain consists of many neurons organized into numerous separate lobes, the functions of which are largely based on the results of lesion experiments.
Because the octopus does not have a hard structure to which recording equipment can be anchored and uses its eight flexible arms to remove any foreign object attached to the outside of its body, in vivo recording of electrical activity from behaving octopuses has been limited until now. not been possible.
Now scientists are recording the very first brain waves of free-moving octopuses. Conducted by the Okinawa Institute of Science and Technology (OIST), the study is crucial to understanding how octopus brains control their behavior. It could provide clues to the common principles needed for intelligence and cognition.
Dr. Tamar Gutnick, first author and former postdoctoral researcher in the Physics and Biology Unit at the Okinawa Institute of Science and 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 evolved completely differently from those of vertebrates.”
“Octopuses have eight powerful and ultra-flexible arms that can reach anywhere on their body. If we tried to attach wires to it, they would immediately pull it off, so we had to keep the equipment out of their reach by placing it under their skin.”
Scientists chose small and lightweight data loggers as a solution, originally designed to monitor the brain activity of birds in flight. The team modified the devices to be waterproof and compact enough to easily slip into the octopuses. Up to 12 hours of continuous recording was possible with the batteries, which had to operate in low air conditions.
Because of its larger size, the researchers decided to use Octopus cyanea, also known as the daytime octopus, as their model animal. Three octopuses were put to sleep before a lumberjack was inserted into a hole in the mantle’s muscular wall. The most accessible part of the octopus’s brain, known as the vertical lobe and median superior frontal lobe, is where the scientists implanted the electrodes.
Upon completion of surgery, the octopuses were returned to their home aquarium and monitored by video. After five minutes, the octopuses had recovered and spent the next 12 hours sleeping, eating and moving around in their aquarium, while their brain activity was recorded. The logger and electrodes were then removed from the octopuses and the data was synced to the video.
The researchers discovered several patterns of brain activity, some of which resembled mammalian patterns in size and shape, while others were slow oscillations with very long amplitudes that had never been observed before.
Dr Gutnick said: “We are not yet able to link these brain activity patterns to specific behaviors from the videos. However, this is not entirely surprising as they did not force the animals to perform specific learning tasks.”
“This is an area associated with learning and memory, so to explore this circuit we need to perform repetitive memory tasks with the octopuses. That’s something we hope to do very soon!”
According to scientists, this method of recording brain activity of free-moving octopuses can be used in other octopus species. It can help determine several facts, including how octopuses learn, socialize, and control the movement of their bodies and arms.
prof. Michael Kuba, who led the project at the OIST Physics and Biology Unit and now continues at the University of Naples Federico II, said: “This is a crucial study, but it is only the first step. Octopuses are so smart, but at the moment we know so little about how their brains work. This technique means we can now look into their brains as they perform specific tasks. That is exciting and powerful.”
- Tamar Gutnick, Andreas Neef, et al. Recording of electrical activity from the brain of the behaving octopus. Current Biology (2023). DOI: 10.2139/ssrn.4309084