Brainless memory

Keeping track of events in the past will allow us to make smarter decisions about the future. Researchers at the Max-Planck Institute for Dynamics and Self-Organization (MPI-DS) and the Technical University of Munich (TUM) have now identified how the slime mold Physarum polycephalum saves memories – even though it has no nervous system.

The ability to store and retrieve information gives an organ a clear advantage when searching for food or avoiding harmful environments. It has traditionally been applied to organisms that have a nervous system.

A new study written by Mirna Kramar (MPI-DS) and Professor Karen Alim (TUM and MPI-DS) challenges this notion by discovering the amazing capabilities of at a highly dynamic single-cellar organism to store and retrieve information about its environment.

Window into the past

The slime mold Physarum polycephalum has been in vogue for many decades. Already at the crossroads of animal, plant and fungal kingdoms, this unique organism gives us a glimpse into the evolutionary history of eukaryotes – to which humans also belong.

Its body is a single large cell made up of interconnected tubes that form complex networks. This single amoeba-like cell could stretch several centimeters or even meters, appearing as the largest cell on earth in the Guinness World Records Book.

Make decisions on the most basic stages of life

The amazing ability of the slime mold to solve complex problems, such as finding the shortest path through mazes, has won the “intelligent” feature. He joined the research community and posed questions about making decisions on the most basic stages of life.

Physarum’s decision-making ability is particularly interesting because its tubular network is constantly reorganizing rapidly – growing and destroying its tubes – while being completely devoid of an organization center. .

The researchers found that the organization weaves memories of a food encounter directly into the network-like architecture of the organization and uses the stored information as they do so. -future closures.

The architecture of the network as a reminder of the past

“It is very exciting when a project develops from a simple experimental perspective,” says Karen Alim, head of the Biological Physics and Morphogenesis group at MPI-DS and professor of Biological Networks Theory at the Technical University of Munich .

When the researchers followed the process of migration and feeding of the organism and observed a specific trace of food source on the pattern of thick and thin tubes of the network long after feeding.

“With P. polycephalum’s highly dynamic network reorganization, the durability of this print inspired the idea that the network’s own architecture could be a reminder of the past,” says Karen Alim. However, first they had to explain the approach behind the shape of the print.

Decisions are driven by memories

For this purpose the researchers combined microscopic observations of the change of the tubular network with theoretical modeling. Encountering food removes a chemical that travels from where food has been found throughout the organism and softens the tubes in the network, causing the organism to regenerate. towards the food.

“The gradual reduction is where the existing tokens of food sources are coming in and where information is stored and retrieved,” says first author Mirna Kramar . “Past feeding events are established in a tube diameter hierarchy, particularly in the arrangement of thick and thin pipes in the network.”

“For the soft chemical now being transported, the thick tubes in the network act as highways in traffic networks, enabling fast transport throughout the whole organism”, adds Mirna Kramar added. “So there have been previous events in the network architecture and so pressure into the decision on the future direction of migration. “

Design based on universal principles

“Given the simplicity of this live network, Physarum’s ability to create memories is fascinating. It’s amazing that the organization relies on such a simple mechanism and yet has control over it in such an elegant way,” said Karen Alim.

“These results reveal an important piece of the puzzle in understanding the behavior of this ancient organism while at the same time identifying universal principles that underpin behavior. We will take a look. on potential applications for the design of smart products and the construction of soft robots that navigate through complex environments. “, concludes Karen Alim.

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Published:

Encoding memory in tube diameter hierarchy of live streaming network

Mirna Kramar and Karen Alim

PNAS, 22.02.2021 – DOI: 10.1073 / pnas.2007815118