Thursday, February 25, 2021

Slime mold can store and preserve memory without brain, scientists say

Margarita Maltceva 

The ability to preserve and restore memory gives living organisms more advantages for obtaining food and avoiding hazardous environments. Scientists usually attribute such skills to multicellular organisms with a nervous system. But a recent discovery by scientists in Germany revealed that a single-celled organism could also possess and retrieve memory.     
© Provided by National Post Physarum polycephalum, slime mold that mostly inhabits on moist dung, soil and wood, uses its tubular network to detect food and store memory about its location.

Researchers Mirna Kramar and Karen Alim released a new study that suggests that Physarum polycephalum, the slime mold that lives on moist dung, soil and wood, “weaves memories of food encounters” into its body and uses those memories to make future decisions.

“Given the simplicity of this living network, the ability of Physarum to form memories is intriguing,” Alim, a biological physics professor at the Technical University of Munch, wrote in a news release.

“It is remarkable that the organism relies on such a simple mechanism and yet controls it in such a fine-tuned manner.”
© Bjoern Kscheschinski Slime mold was given the title ‘intelligent’ as it can solve complex tasks, like finding the shortest path from a maze.

For many decades, Physarum polycephalum has been sparking interest in the scientific world.

According to science educator Ward’s Natural Science , the mold, which moves and consumes solid food particles like other amoebas, eats bacteria, fungal spores and other decomposing organic matter. It slides towards its food, envelops it and releases ferments to digest the nutrients. When the food is digested, Physarum dumps the waste particles and moves away.

Its body contains a single cell and consists of interconnected tubes that create a complex network, ScienceDaily reported. This cell may spread for several centimetres or even meters.

Physarum polycephalum can also solve complex tasks, including finding the shortest path through the maze, according to ScienceDaily. This skill gave the mold title “intelligent” and prompted researchers to examine its memory.

Researchers have monitored Physarum’s migration and feeding processes to identify the decision-making abilities on the most elementary levels of life. They observed different imprints of the food source on thicker and thinner tubes of the mold’s network after it feeds.

“Given P. polycephalum’s highly dynamic network reorganization, the persistence of this imprint sparked the idea that the network architecture itself could serve as memory of the past,” Alim said, as quoted by the news release.
© Bilderfest Karen Alim, professor at Technical University Munich, observes Physarum polycephalum in her laboratory.

In order to better understand how the mold stores its memories, the scientists had to explain the mechanisms that form that imprint.

As a part of the experiment, they merged microscopic observations of the mold’s tubular network with theoretical modelling. They discovered that when Physarum detects food, it releases a chemical that goes from the location where the food was spotted throughout the network, softening the tubes. It makes the entire organism redirect its movements towards the food.

“The gradual softening is where the existing imprints of previous food sources come into play and where information is stored and retrieved,” said Kramar, a biological physics researcher at Max-Planck Institute, as quoted by the news release. “Past feeding events are embedded in the hierarchy of tube diameters, specifically in the arrangement of thick and thin tubes in the network.”

“For the softening chemical that is now transported, the thick tubes in the network act as highways in traffic networks, enabling quick transport across the whole organism,” she added. “Previous encounters imprinted in the network architecture thus weigh into the decision about the future direction of migration.”

Alim said that the results of the experiment play an important role in understanding the manner of this ancient organism.

“We envision potential applications of our findings in designing smart materials and building soft robots that navigate through complex environments,” she added.

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