Memories are what make us humans. Remembering our past, recognising the highs and lows we’ve been through, knowing what we love or hate and so on. But in the larger animals and plant kingdom, memory is a survival tool. Any organism must remember the paths they must take to find food or avoid danger. Knowing and recognising safe vs harmful conditions/food/animals etc is key to living. Mostly, the function of memory is recognised as an attribute of organisms with a functional nervous system, but the latest research shows it can be found in a single-celled organism as well.
The organism in question is a slime mold named Physarum polycephalum.
The thing is somewhere in the intersection between plant, animal, and fungus kingdoms. Researchers think this organism can hold evolutionary clues about eukaryotes (all multicellular organisms like plants and animals—even humans). According to the Guinness Book of World Records, this single-celled animal is the “largest cell on earth.” Its whole body, including the intricate networks formed with tubes and such, is basically one large cell. It can be a few centimetres or several metres long.
The research team gave this mold puzzles; such as finding the shortest path through a maze. They dubbed the decision-making process of Physarum as ‘intelligent'.It can evidently restructure its tubes to form new networks based on every encounter with food. They followed the migration and feeding process of the mold and discovered there was a distinct “imprint” after every encounter. It was visible by thick and thinned restructured networks after a feed.
“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,” says Karen Alim. The results impressed the team as it makes the concept of memory completely different from how we understand it.
They emphasised how this creature was a very simplistic living network; which makes its ability to store memories even more intriguing. Alim believes these observations can have an impact on designing smarter robots that can navigate through complex environments.
The study is published in Proceedings of the National Academy of Sciences.