What food coma in sea slugs teaches us about memory
By Nikolay Kukushkin | Published: 2025-03-10 17:30:00 | Source: Neuropsych – Big Think
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When we think about memory, we often assume that superior memory means remembering more things for longer. This is also how we think about computer memory: the more, the better. But biologically, memory did not evolve simply to store information. It chooses which information to store and which to discard, a form of pattern recognition. So, superior memory doesn’t just mean… more The information is stored successfully however Most relevant The information has been successfully selected.
I first encountered this tension a few years ago in an unexpected corner of science – while Study of insulin-like hormones in Aplysia californiaa type of sea slug, in Tom Caro’s lab at New York University. The hormones were released after the slugs enjoyed the meal and did several things at the same time:
- They enhanced sugar removal, just as the hormone insulin does in humans.
- They promoted neuroplasticity and nerve cell growth.
- They slowed down the animals.
The first effect is the legal response to food, and it is evident that it has been preserved throughout the tree of life in a remarkably intact way. Insulin-like hormones told the sea slug’s cells to absorb the nutrients it consumed. In the laboratory, we can even cause the release of these hormones in the sea slug using an anti-diabetic drug used in humans. It is one of those examples that reveal the unity of life on Earth.
The second effect relates to memory enhancement, which is consistent with the first effect. Since the food was successfully found, it is assumed that the sea slug wanted to form a long-term memory, and insulin-like hormones helped in this. Combining these influences made sense.
The latter effect was strange and a bit ironic considering that sea slugs are already very slow. However, the difference was evident when they were recorded on camera for several hours. Watching and analyzing these videos, even at 20x the original speed, was probably the most boring experience of my life. Since we were able to prevent this effect using insulin-like receptor inhibitors, it wasn’t just a matter of digestion or the meal weighing the sea slug’s physical weight. It must be said that these creatures can consume a huge amount of nori per body weight, but that was not the problem.
Instead, the effect was a coordinated food coma induced by tailored hormones. Evolution has built the response into molluscs. But why did the animal need to become unresponsive, reduce neuronal excitability, and stop moving after a meal? Why did animals develop this seemingly adverse response to food?
The only explanation I can think of is that memory is expensive. It takes energy, as does moving around and exploring your environment. However, once food is found and consumed, memory must be prioritized over active exploration. Sea slugs didn’t need to try new things; They needed to maintain past experience for future gains. Thus they diverted energy away from movement and into memory.
This was in 2019 when we didn’t know about GLP-1 agonists like Ozempic, which are insulin-related hormones that cause food comas while also promoting neuroplasticity and memory. I wonder if the whole set of effects would make immediate sense if we conducted the study today.
When we were working on the study, my boss, Tom Caro, and I discussed the “expensive memory” explanation. He questioned the idea that learning requires so much energy that it can be drawn from behavior. I get his point: At least on the surface, it seems that manipulating the precise configuration of neurons and synapses—this is how learning creates memory—should cost dramatically less energy than, say, muscle movement, just as a computer uses less energy than an electric car.
But computers can, in fact, consume large amounts of energy. Likewise, there is reason to believe that biological memory may be so “expensive” that it requires siphoning off energy from other sources. For example, fruit flies have two forms of long-term memory: one is more stable, and the other is cheaper and requires less energy. If the first It wasn’t very expensive To use it all the time, why have two?
We also know that organisms make information processing trade-offs based on energy use. Yeast, for example Credits Their power budget with the accuracy of cellular signals. When they run out of food, their interpretation of environmental cues becomes “more flexible.” If information processing were cheap, there would be no need to reduce it in such cases.
Memory may also be a luxury, and reduced mobility provides a way to save memory when it matters most.
Mnemonic economics
A strange food coma in sea slugs has affected the way I think about memory. Memory may be so expensive that, in some situations, it requires an organism-wide allocation of energy. In this case, minds must confront similar economic considerations in other, less extreme cases. The cost-benefit of memory formation is constantly evaluated according to the organism’s energy budget.
For us humans, choosing some styles over others is more important than choosing a sea slug. We process much more information per unit of time than a slug does. Many things pass through our brains at any given moment, and in order to understand them, they must be generalized and abstracted, which means that other things must be forgotten. Not only would it be very expensive to remember everything. It will be useless.
I think we forget this because we don’t realize that our memory is limited. We don’t run out of memory like computers do, and suddenly, you can’t remember anything new. However, we remember different things to different degrees, and this is our brain’s way of sorting through the endless stream of information. Even if we treat our memory as a limitless hard drive, our brains quietly sort our mental files into “to save” and “to forget.”
Is there anything practical to be gained from this vision?
The learning we normally attempt—like trying to cram an entire textbook into the weekend before finals—is unnatural. The brain’s goal is to pick out a salient pattern, and the textbook is not what it considers salient.
Instead, the best way to “improve your memory” is to listen to yourself. Use the powers of your mind — curiosity, inspiration, even boredom — as tools. When you’re curious, learn as much as you can. When you feel inspired, abandon other activities. When you get bored, change your focus to something else. And don’t forget to take breaks – Just like a sea slug, taking time to rest after a study session allows your brain to digest new information, which enhances memory and slows down forgetting.
On the other hand, if memory is expensive and selective, perhaps we should be more thoughtful about what we allow into our brains. I suspect that in the future, we will set stricter societal standards for mental hygiene and learn to treat unwanted memories like junk food.
For example, at least a third of my memory is occupied by TV commercials from the 1990s. Could this space have been used for something else? I’ll never know, and it might not matter much. But if someone had told my parents back then that commercials would actually crowd out other information from my mind, I bet they would never have let me watch TV again.
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