Processing information by flow: the smart slime mold <i>Physarum</i>

Simple organisms manage to thrive in complex environments. Propagating and remembering information about the environment is key to take decisions. The network-shaped slime mold Physarum polycephalum excels as a giant unicellular eukaryote being even able to solve optimization problems despite the lack of a nervous system. To uncover how Physarum accomplishes these tasks we combine experimental observations of the organism’s response to nutrients with theoretical modelling of network adaptation and fluid flows pervading the network. We find that flows are the mean to propagate information about the location of a nutrient source. Information that is subsequently memorized in the pattern of thicker and smaller tubes of the network’s architecture. As the pattern of tube size determines organism behavior such as migration direction, these memories are forming the basis for behavioral decisions.