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Slime research may not be the sexiest science, but produces some really wild results. So wild, in fact, a new study reconfigures our understanding of not only animal intelligence, but also memory idea.
What’s up – The study, published Monday in the journal Proceedings of the National Academy of Sciences, investigates how, exactly, giant slime molds (Physarum polycephalum) encode memories in response to food sources.
This study offers clues to how biological signals can generate and alter memories of even the simplest creatures, the researchers say.
Karen Alim is co-author of the study and a professor at Technische Universität München, Germany. She says Reverse the study takes what we already knew about these curious life forms, and turns it around.
“There is previous work that the biological signals in slimy molds can store information about past experiences,” says Alim. “Yet the fact that the network architecture can store memories is [a] new concept against the background of slimy mold and fungus. “
How they did it – Alim and his team both observed slimy mold in a lab and generated a theoretical model to aid their calculations.
Using images generated from their observations and the model, they determined the changes in the tubes of the organisms (essentially, the silt tendrils emanating from the organism as it makes its way through an environment) in response. to a newly introduced food source.
First, the scientists calculated the changes in the diameter or size of these tubes in response to the new food source, as well as what the slimy mold did over the course of several hours.
It took the slime mold 45 minutes to rearrange its entire network of tubes to cope with the food source, they found. At around 90 minutes, the mold began to migrate to the food source. And after 310 minutes, the slimy mold had almost completely engulfed the food source.
Surprisingly, when scientists reduced the size of the mold, the organism reorganized itself even faster – the smaller slimy mold began to reorganize its tubes within 15 minutes and began to move towards the food source in 45 minutes, according to the study.
Slime molds are known to ‘make decisions even between 10 and 20 [minutes]”, According to the study. But what motivated these decisions was more obscure. These new results offer clues. As the researchers in the study explain, slimy molds appear to accomplish their remarkable reorganization by encoding the location of the source food through the network of tubes.
Dig into the details – To test this idea, the scientists used their simulated mold to show how a mysterious agent from the food source would likely have entered the slimy mold tubes. In the simulation, the researchers released a softening agent, which caused the tubes closest to the food to expand or dilate.
Tubes farther from the food source do not expand as much as those closer to the food, essentially establishing a hierarchy of tubes. The tubes clogged then print memory of the source of nutrients in its network.
But it’s not just a one-off response. Rather, the slime mold “irreparably changed” the flow patterns of its tubes, according to the study – a sign of long-term memory formation.
These findings unlock a “missing piece of the puzzle” for how slimy molds constantly reorganize in response to nutrients.
In short: slimy molds encode memories of nutrient sources in their tubes. The tubes that survive the longest are those “directly carrying the memory of the nutrient stimulus that led to their growth,” according to the study.
“Therefore, the memories stored in the hierarchy of tube diameters, and in particular at the location of the thick tubes, are then layered on top of each other, with each new stimulus differentially strengthening and weakening the existing thick tubes on top of each other. of existing memories. ”
Why is this important – This study suggests that memory formation is possible in creatures without a nervous system – creatures like fungi or slimy molds.
“I believe our study is changing our perception of all the flow networks in life, whether it’s our own vascular system or the networks formed by slimy molds or fungi,” says Alim.
In most animals, memory is typically formed as a result of synaptic plasticity, whereby the brain makes connections between specific neural and synaptic networks that strengthen over time.
Slimy molds lack synapses – or a nervous system at all. But this study shows that they effectively mimic synaptic plasticity by encoding memories in their tube arrays instead.
It was previously thought that memory formation only existed in higher level organisms like us, but now researchers are familiarizing themselves with the idea even the simplest forms of life have memory.
And after – The study gives researchers more momentum to explore slimy mold in science. Slimy mold, for example, is able to solve the two-armed bandit (also known as “ multi-armed ”) problem, which is a related problem complex decision making.
Slime molds are also incredibly good at finding the shortest path between food sources in a maze. These molds, in turn, help mathematicians overcome the problem of the traveling salesman, who seeks to find the shortest route for delivery drivers between cities.
More immediately, the researchers behind this study want to understand the chemistry involved in the tubes when they change shape in response to food. Scientists believe that the chemical agent that softens the tubes is adenosine triphosphate, an energy-carrying chemical. Future research could delve into the other properties and uses of this strange substance.
The researchers believe their findings may have unimaginable implications for biologically inspired design in other fields as well, such as robotics. Much of the current research in artificial intelligence focuses on models that mimic the nervous system, but this study provides an innovative new source of inspiration for AI researchers.
“A lot of research is aimed at designing flexible robots or building autonomous and intelligent systems. I believe the information storage mechanism that we discovered in Physarum will be very inspiring for this field, ”says Alim.
Abstract: The concept of memory is traditionally associated with organisms possessing a nervous system. However, even very simple organisms store information about past experiences to thrive in a complex environment – successfully harnessing nutrient sources, avoiding dangers, and warding off predators. How can simple organisms encode information about their environment? Here we follow how the giant single-celled slime mold Physarum polycephalum responds to a source of nutrients. We find that the body’s networked plane of the organism itself serves to encode the location of a source of nutrients. The body consists entirely of intertwined tubes of different diameters. Now, we observe that these tubes grow and shrink in diameter in response to a nutrient source, thus imprinting the location of the nutrient in the hierarchy of tube diameters. By combining theoretical model and experimental data, we reveal how memory is encoded: a source of nutrients locally releases a softening agent which is transported by cytoplasmic flows within the tubular network. Tubes receiving a lot of softening agent grow in diameter to the detriment of other tubes which shrink. Thus, the capacities of the tubes for flow-based transport are continuously improved to the location of nutrients, reorienting future decisions and migration. This demonstrates that the location of nutrients is stored and retrieved in the hierarchy of tube diameters of the networks. Our findings explain how network-forming organisms like slimy molds and fungi thrive in complex environments. Here we identify a version of associative memory flow networks – most likely relevant to the plethora of living flow networks as well as bioinspired design.
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