Brainless slime mould has an external memory
By Ella Davies, BBC Nature
9 October 2012
|Slime Mold_Paul Zahl-NG-Getty Images|
"The whole organism is made up of bits of pulsating tissue, which are constantly expanding and contracting, using a similar mechanism to our own muscle cells," explained PhD student Christopher Reid.
"Each part changes the speed at which it pulsates according to what it can sense in the environment around it - for example food, light or heat - which are detected by chemical receptors on the cell's surface."
"The pulsating parts are also influenced by the throbbing of their neighbours within the cell, which means that they can communicate with each other, to pass information through the organism about what is happening in the environment outside. The different speeds of contraction directly influence which direction the cell will then move in."
"In essence, the slime mould is memorising where it has been - storing this memory in the external environment and recalling the information when it later touches the slime-coated area.
"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," he told BBC Nature.
"It is truly a remarkable creature that is redefining our notions of 'intelligence'."
Slime mold uses an externalized spatial “memory” to navigate in complex environments
Chris R. Reid, Tanya Latty, Audrey Dussutour, and Madeleine Beekman
Behaviour and Genetics of Social Insects Laboratory, School of Biological Sciences, and Centre for Mathematical Biology, University of Sydney, Sydney, NSW 2006, Australia; and Centre de Recherches sur la Cognition Animale, UMR 5169 Centre National de la Recherche Scientifique, Université Toulouse III, 31062 Toulouse, France
Edited by John G. Hildebrand,
of Arizona, ,
and approved September 7, 2012 (received for review June 24, 2012) Tucson, AZ
Spatial memory enhances an organism’s navigational ability. Memory typically resides within the brain, but what if an organism has no brain? We show that the brainless slime mold Physarum polycephalum constructs a form of spatial memory by avoiding areas it has previously explored. This mechanism allows the slime mold to solve the U-shaped trap problem—a classic test of autonomous navigational ability commonly used in robotics—requiring the slime mold to reach a chemoattractive goal behind a U-shaped barrier. Drawn into the trap, the organism must rely on other methods than gradient-following to escape and reach the goal. Our data show that spatial memory enhances the organism’s ability to navigate in complex environments. We provide a unique demonstration of a spatial memory system in a nonneuronal organism, supporting the theory that an externalized spatial memory may be the functional precursor to the internal memory of higher organisms.