Octopuses have long been a subject of fascination. From deceiving predators to learning from past experiences, they display many behaviors associated with high intelligence [1]. This has sparked curiosity about their brain function and perception of reality. Octopuses also have large brains relative to their body size. The most complex of any invertebrate, their brains contain over 30 different lobes, and as many as 42 different types of brain cells [2]. Octopuses not only have a large centralized brain but also clusters of neurons in each of their eight arms, which are believed to function partially independently from the central brain [3]. Due to the relative independence of their arms, it has even been suggested that they experience multiple levels of consciousness [3]. But how can we know what’s really going on in their heads? Despite the fascination with octopus brains and intelligence, there is little conclusive data. Knowledge of the inner world of octopuses is still extremely limited and has been largely based on behavioral observations and lesioning experiments [1] [4].

There have, however, been recent insights into the minds of these mysterious cephalopods. Researchers from Japan, for instance, have recently successfully measured the brainwaves of a free-moving octopus using innovative electrode technology [4]. A common practice for observing neural behavior in animals, recording brain waves allows researchers to record brain activity. When recorded in conjunction with behavioral data, it can help determine the types of brain activity present during different behaviors. However, recording octopus brain waves has posed a massive challenge to researchers. Namely, octopuses are invertebrates, and their lack of a skull makes it extremely challenging to implant a neuroimaging device into their heads. Until now, researchers have been unable to implant a neuroimaging device into an octopus brain while also allowing it to freely move. The ability to successfully measure the brainwaves of these free-moving octopuses is thus what makes this new experiment so revolutionary. It’s the first time the brain activity of an octopus has been recorded alongside their behavior as they are allowed to move freely in a tank [4].

To study the brain activity of these creatures, researchers surgically implanted a data logger into the dorsal mantle cavity of three octopus cyanea, a large tropical species of octopus [4]. The dorsal mantle cavity is where the brain and many other vital organs are housed. From here, electrodes used for measuring brain electrical activity were implanted into the vertical lobe system of the brain. After recovery from surgery, the octopuses were allowed to move freely about their tanks, exploring and resting as they wished. The brain activity and behavior of these octopuses were recorded simultaneously for about 12 hours. These two recordings were carefully matched up so brain activity could be compared with different behaviors [4]. 

Familiar brain waves resembling those found in mammal brains were recorded, as well as a novel brainwave [4]. This large amplitude, 2 Hertz brainwave has never before been recorded in any other organism. While these results are exciting, they raise more questions than answers. Researchers were unable to draw a correlation between the octopus brain activity and behavior, so it’s unknown what this new brainwave could mean. Episodes of this 2 Hertz oscillation appeared during a variety of behaviors  [4].

Although the results of this experiment are inconclusive, the neuroimaging techniques developed could lead to important future discoveries [4]. It is yet to be seen how reproducible this method of electrode and data logger implantation is, but researchers hope that in future experiments, they will be able to implant the electrodes deeper into the octopus’s brain, picking up activity that could be more easily connected to reward systems, memory consolidation, motor function, and more. However, the researchers also presented concerns that implanting electrodes into an area of the brain that controls behavior could disrupt that area’s function, rendering the data useless [4]. The ethics of repeating this experiment should also be considered. It’s widely recognized that octopuses are highly intelligent creatures that potentially experience high levels of consciousness and awareness [1]. As this study requires octopuses to undergo brain surgery, it is unlikely that researchers were able to completely eliminate the octopus’s suffering.

Repeating this study could potentially lead to a far greater understanding of octopus behavior, intelligence, and even consciousness. As this is a novel technique, it’s challenging to compare or interpret the results, but researchers believe their technique of implanting electrodes into an octopus’s brain may lead to future discoveries. Future experiments could potentially answer long-held questions about octopus behaviors and cognition while providing further insights into nonhuman intelligence and the convergent evolution of intelligence.

References: 

1. Schnell, A. K., Farndale Wright, N. R., & Clayton, N. S. (2023). The inner lives of cephalopods. Integrative And Comparative Biology, 63(6), 1298–1306. https://doi.org/10.1093/icb/icad122
2. Styfhals, R., Zolotarov, G., Hulselmans, G., Spanier, K. I., Poovathingal, S., Elagoz, A. M., De Winter, S., Deryckere, A., Rajewsky, N., Ponte, G., Fiorito, G., Aerts, S., & Seuntjens, E. (2022). Cell type diversity in a developing Octopus Brain. Nature Communications, 13(1). https://doi.org/10.1038/s41467-022-35198-1
3. Carls-Diamante, S. (2022). Where is it like to be an octopus? Frontiers in Systems Neuroscience, 16. https://doi.org/10.3389/fnsys.2022.840022
4. Gutnick, T., Neef, A., Cherninskyi, A., Ziadi-Künzli, F., Di Cosmo, A., Lipp, H.-P., & Kuba, M. J. (2023). Recording electrical activity from the brain of behaving octopus. Cell, 33(6), 1171–1178. https://doi.org/10.1016/j.cub.2023.02.006