They only have a single cell — no brain, but slime molds “remember” where they’ve been.
How? The brainless slime mold Physarum polycephalum constructs a form of spatial “memory” by avoiding areas it has previously explored, researchers at University of Sydney and Université Toulouse III have discovered.
“As it moves, the plasmodium leaves behind a thick mat of nonliving, translucent, extracellular slime,” the scientists said in Proceedings of the National Academy of Sciences, October 8.
“As the plasmodium is foraging, we found. that it strongly avoids areas that contain extracellular slime. This avoidance behavior is a ‘choice’ because when no previously unexplored territory is available, the slime mold no longer avoids extracellular slime.”
The finding is strong support for the theory that the first step toward the evolution of memory was the use of feedback from chemicals.
“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.
“Our discovery is evidence of how the memory of multi-cellular organisms may have evolved — by using external chemical trails in the environment before the development of internal memory systems,” said Reid.
“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.”
Setup for the U-shaped trap navigational task. The red dashed line shows the predicted optimal path. (Credit: Chris R. Reid et al./PNAS)
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.
Text and Image via Kurzweil News. Continue HERE