By remembering past events, we can make better decisions about the future. To the best of our knowledge, the concept of memory is associated with living organisms with a nervous system. However, a new study published in the journal Proceedings of the National Academy of Sciences suggests that this is not always the case.
Led by Mirna Kramar, researcher at the Max Planck Institute for Dynamics and Self-Organization in Germany (MPI-DS) in collaboration with Professor Karen Alim from the Technical University of Munich (TUM), this shows the impressive ability of the slimy mold Physarum polycephalum to memorize information despite the lack of a nervous system.
A unicellular organism like no other
Physarum polycephalum has fascinated scientists for centuries. This organism belongs to the amoeba taxonomic group, the same group as the amoeba, and is located at the crossroads between animals, plants and fungi. Its body is made up of a single cell made up of interconnected tubes that form complex branches. In passing, note that Physarum polycephalum can stretch for several centimeters or even meters. The most fascinating trait, however, is the ability to memorize things.
A very special form of memory
Specifically, this unicellular myxomycete species, which lives in cool and humid environments, can remember the location of the nutrients. Memory is encoded in the body’s morphology. It is expressed by the diameter of the branch pipes. In other words, once the mold has discovered a place where nutrients are present, it quickly reorganizes its tubular network, expanding some tubes and narrowing others.
Plasmodium of the mucous membrane of the species Physarum polycephalum. By frankenstoen / Flickr, CC BY 2.5
According to our source, this architecture is retained even after the food is exhausted. It turns out that this form of memory enables the Physarum polycephalum to find the shortest route to a place where there is food, or the optimal route out of a maze.
A still unsolved mystery
“In the brain, we store information by strengthening or weakening the connections between neurons – a type of nerve cell that sends out electrical and chemical signals,” said Alim. According to her, there is a similar but simplified process with the blob. “The results remind me of the network of paths between ants, in which the foraging ants deposit a trail of chemicals so that other ants can follow them,” confided in her turn to Live Science Audrey Dussutour of the University of Toulouse.
Although scientists know what kind of pheromones ants secrete to mark their trails, they still don’t know what kind of signal or chemical the Physarum polycephalum uses to memorize trails. A puzzle that will be explored in future studies.