Their bizarre bodies, blobby shape and unique intelligence rank octopuses among the most beloved creatures of the ocean. The 2020 documentary "My Octopus Teacher" was showered with accolades for its poignant story depicting a filmmaker's affectionate relationship with an octopus. Part of the octopus' charm is in its contradictions: they are surprisingly alien-looking, yet express so much curiosity and problem-solving prowess — human traits if there ever were any. Humans see something familiar yet distorted in the intelligence of cephalopods, like a funhouse mirror of self-awareness.
Those iconic, flexible tentacles are chock full of neurons as well, allowing octopus appendages to behave like they have a mind of their own. But their brains are especially weird because they aren't organized the same way primate brains are. Many people speculate that their complex neuroscience, which evolved so differently from our own, is the closest humans will ever get to encountering an intelligent alien.
It's not easy to install an electrode implant on something that doesn't have a skull where electrical wires can be anchored.
Hence, the octopus' brain is the subject of study from animal neuroscientists — and one of the main ways we've learned about octopus brains is through lesioning studies. This is when scientists intentionally cause brain damage to the creature, precisely destroying clusters of neurons, to see what stops working. In fact, ablative brain surgery is largely how early neuroscientists gained their bearings when first mapping the brain; this involved selectively excising certain sections of animal brains and observing what limbs or body parts ceased functioning.
But brains are extremely complex, and this blunt way of smashing neural connections oversimplifies how brains work. Fortunately, today we have better ways of figuring out how cognition occurs — in particular, the fMRI machine. Short for functional magnetic resonance imaging, these machines let scientists see in real-time, and in three dimensions, how neurons fire as one is thinking or moving one's body. They are tremendously powerful tools for advancing what humans know about cognition, both in animals and in people. Indeed, domesticated animals like dogs can be trained to lay still in the noisy fMRI machine long enough for scientists to observe their brain activity in response to certain stimulation.
But when it comes to wild animals, like octopuses, studying their brain in real-time is a challenge. It would be preferable if we could record brain activity of octopuses by measuring electrical signals while documenting an associated behavior, similar to when we put people or dogs into fMRI machines. But this is easier said than done when messing with the brains of slimy, crafty mollusks like octopuses. (Yes, while they're related to squids and cuttlefish, octopuses also have a lot in common with snails and clams.)
Now, for the first time, researchers found a way to record the brain activity of free-moving octopuses thanks to the work of an international team from Germany, Italy, Japan, Switzerland and Ukraine. Their study, recently published in the journal Current Biology, documents a new way to record octopus brain activity for up to 12 hours. But while this experiment was groundbreaking, it's also not clear yet what exactly these signals mean.
"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," Dr. Tamar Gutnick, the study's lead author and a former postdoctoral researcher in the Physics and Biology Unit at the Okinawa Institute of Science and Technology, said in a statement.
Some of the brain waves resembled the size and shape of mammalian brain activity, but other pulses from the neurons of octopuses were completely bizarre.
For this experiment, the researchers chose three big blue octopuses (octopus cyanea), which often appear a mottled brown, but have exceptional camouflage with the potential to quickly alter their color and skin texture. These tropical cephalopods are sometimes called "day octopuses" because they hunt while the sun is out. Remarkably, octopuses are color blind. So how do they know to morph into a bluish magenta hue or transform into a chunk of coral shrapnel? They can sense the different directions light waves vibrate, a property known as polarization. Even their basic perception is radically different from ours.
Imaging their brain activity was not a simple task. Lacking a skull, octopuses' brains are wrapped in a thin capsule of cartilage. It's not easy to install an electrode implant on something that doesn't have a skull where electrical wires can be anchored. Octopuses (the correct plural, not octopi) are boneless invertebrates that are able to squeeze themselves into the thinnest of crevices, which has given them a reputation for being exceptional escape artists.
To make matters more complicated, you can't attach something to the body of an octopus for long because it will easily pluck it off with one of its eight arms. So recording the electrical activity of octopuses has thus far not been possible.
But the researchers found an intriguing workaround to implant a data logger (originally designed to track the flight of birds) and some electrodes for measuring brain activity. First, the researchers made a small incision between its eyes and then inserted the devices adhered onto a plastic card with super glue. They were implanted into the brain lobes of the octopus, specifically the vertical lobe and median superior frontal lobe. This area is believed to be responsible for birthing new brain cells, as well as playing a role in memory and learning.
Afterwards, the octopuses were returned to their tanks and allowed to recover while being filmed. They quickly came to, behaving normally, sleeping, grooming or exploring their aquariums. Some checked out their incisions with their arms, but they didn't attempt to remove the logger or electrodes.
Gutnick and his colleagues were able to pick up clear signals of brain activity, but deciphering these patterns is another story. Some of the brain waves resembled the size and shape of mammalian brain activity, but other pulses from the neurons of octopuses were completely bizarre. These were long-lasting, slow oscillations with large amplitudes, which indicates relatively strong electrical activity. These have not been reported before.
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Unfortunately, the researchers were unable to find a strong correlation between this activity and the way the octopuses were behaving. Even when the octopuses were moving around, they could find no obvious changes in signal, despite drastic changes in motion or remaining still. There are still a lot of mysteries to untangle, but this proof of concept could be applied to many other octopuses, including other species, to learn more. We may soon learn much more about how octopuses socialize, learn and move their arms around.
If the researchers had incorporated more specific tasks with these octopuses, rather than just letting them do their own thing, it might be easier to tease out relationships between brain activity and behavior. Gutnick emphasized, "we really need to do repetitive, memory tasks with the octopuses. That's something we're hoping to do very soon!"
Octopuses are such bizarre and unique creatures that can teach us a lot about our own cognition and evolution. Applying the lessons from cephalopod neuroscience could open doors to improving medical research, especially in the realm of machine intelligence and neuroplasticity, or the ability for brains to reorganize, heal and strengthen connections. But clearly we are still scratching the surface when it comes to understanding what's going on inside an octopus brain.