Brainless Slime Molds Shed Light On The Evolution of Memory
“We have shown for the first time that a single-celled organism with no brain uses an external spatial memory to navigate through a complex environment,” said Christopher Reid from the University’s School of Biological Sciences.
…“Results from insect studies, for example ants leaving pheromone trails, have already challenged the assumption that navigation requires learning or a sophisticated spatial awareness. We’ve now gone one better and shown that even an organism without a nervous system can navigate a complex environment, with the help of externalized memory.”
The research method was inspired by robots designed to respond only to feedback from their immediate environment to navigate obstacles and avoid becoming trapped. This “reactive navigation” method allows robots to navigate without a programmed map or the ability to build one and slime molds use the same process.
When it is foraging, the slime mold avoids areas that it has already “slimed,” suggesting it can sense extracellular slime upon contact and will recognize and avoid areas it has already explored.
…“We then upped the ante for the slime molds by challenging them with the U-shaped trap problem to test their navigational ability in a more complex situation than foraging. We found that, as we had predicted, its success was greatly dependent on being able to apply its external spatial memory to navigate its way out of the trap.”