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put-down may lose some of its bite in the future, because our research has demonstrated that the true slime mold, a giant unicellular organism with multiple nuclei, is able to solve a maze and other combinatorial optimization problemsâ¦While it lacks a nervous system, legs or eyes, the plasmodium is still able to move its mass to wherever it finds food. The mere oddities of this strange-looking animal have provided sufficient material for several research papers, even without my having gained any special insights into its behavior, so we have continued to observe it closely. It was about four years ago, as I merely cultivated and observed the plasmodium, that the unexpected and surprising cleverness that it displayed gave me the idea of publishing what we had learnedâ (p. 8). The first quote in the main text is from âMaze-Solving by an Amoeboid Organism,â by Nakagaki et al. (2000, p. 470). Nakagakiâs second quote is from âIs Slime Intelligent?â by Viegas (2000, p. 1).

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P. 103: SLIME MOLDâS EFFICIENT TUBING NETWORK

Nakagaki et al. (2004) write: âHow does the organism obtain the smart solution? Two empirical rules describing changes in body shape are known: 1) tubes of open ends are likely to disappear in the first step and 2) when two or more tubes connect the same two food sources, the longer tubes tend to disappear. These changes in the tubular structure of the plasmodium are closely related to the spatio-temporal dynamics of cellular rhythms. Shuttle streaming of protoplasm, which is driven by hydrostatic pressure induced by rhythmic contraction, may affect the morphogenesis of tubular structures. Hence a key mechanism underlying network formation may involve the spatio-temporal dynamics of oscillatory fields with complex shapes and moving boundaries. The Physarum plasmodium can construct an efficient transportation network which meets the multiple requirements of short length of network and low degree of separation between food sources, as well as tolerance of accidental disconnection at random position. The plasmodium can achieve a better network configuration than that based on the shortest connection of Steinerâs minimum tree, which is impressive considering that it is very hard for humans to deduce Steinerâs connections for just a few locations. This amoeboid organism must be quite smartâ (pp. 4â5). Nakagaki et al. (2001) write: âBiochemical oscillators in the plasmodium may give rise to propagating waves by spatial interactions of diffusion and advection via protoplasmic streaming. These intracellular waves can be initiated by some external stimulation including the addition of nutrients, the increase of light intensity, humidity, or temperature. The traveling wave leads to the development of a tubular structure in the sheet-like parts. Therefore, the geometry of the tube network drastically changes, depending on the external perturbation.. The path-finding mechanism is closely related to the contraction waves in the plasmodium. The addition of the nutrient leads to a local increase in the contraction frequency which initiates wave propagation from the site of higher frequency. This induction of waves is explained by the theory of phase dynamics. Such contraction waves make the tube modified, since the tube is reinforced or decayed when it is parallel or perpendicular to the direction of propagation of the contraction waves. Therefore, effects of complex behavior of contraction waves in a maze on tube formation play a key role for path-finding in the true slime moldâ (pp. 47â48, 50â51).

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P. 105: COMPUTATION BY SLIME MOLD

Nakagaki (2001a) writes: âEven for humans it is not easy to solve a maze. But the plasmodium of true slime mold, an amoeba-like unicellular organism, has shown an amazing ability to do so. This implies that an algorithm and a high computing capacity are included in the unicellular organismâ¦From the viewpoint of computational science, the plasmodiumâs method of computing is interesting because there is no central processing unit like a brain, but rather a collection of similar parts of protoplasm.