A single-celled organism without brain has external memory
A single cell slime mould has been found to display a form of external memory.
Even though the organisms have no brain, they leave behind a trail of slime residue to help them remember where they’ve been. For the experiment, researchers from the University of Sydney in Australia placed the slime moulds into a maze with a sugary food source on the other side.
As the slime mould moved over the maze, it left behind a trail of slime. The trail served as a way for them to remember the path they had taken, and the researchers say the mould did not travel back over the slimy places. Scientists covered another maze in slime, and it took the moulds ten times longer to find the food because they could not tell where they had already been.
"For a single-celled organism, it has continually surprised researchers with its abilities, such as solving mazes, anticipating periodic events, and even making irrational decisions like we do," PhD student Christopher Reid told BBC Nature.