Imagine a creature that can solve mazes, optimize networks, and “remember” where it last ate — all without a brain or nervous system.
This isn’t science fiction; it’s Physarum polycephalum, a type of slime mold.
Despite its simplicity, this organism has stunned researchers with its ability to process information and adapt to its environment.
A recent study by Mirna Kramar and Karen Alim of the Max Planck Institute for Dynamics and Self-Organization sheds new light on how this extraordinary feat is achieved.
Here’s the immediate takeaway:
Slime molds encode past food locations by physically altering their internal structure.
When parts of P. polycephalum come into contact with food, the tube-like network it uses to move and transport nutrients undergoes a transformation.
The walls of these tubes soften, allowing them to widen. These widened tubes act as memory markers, influencing the mold’s growth patterns long after the food is gone.
Let’s break this down. The organism moves by expanding along its widest tubes and retracting from narrower ones. So, by recording the location of food as wide tubes, the slime mold effectively “remembers” where to go in the future.
This discovery not only deepens our understanding of slime molds but also hints at broader biological principles with applications far beyond these humble organisms.
Challenging What We Thought We Knew About Memory
When you think of memory, you probably imagine neurons firing in a complex network, storing and retrieving information.
That’s the classical view, rooted in our understanding of brains. Slime molds defy this assumption.
They demonstrate that memory doesn’t require neurons at all — it can be encoded in the very structure of an organism.
For years, scientists believed that the problem-solving abilities of slime molds were purely stimulus-response behaviors.
The organism detects a gradient of chemical signals and simply follows it, much like how a moth is drawn to light.
But this explanation falls short when you consider their ability to navigate mazes, optimize network pathways, and revisit food sites even after the stimuli have dissipated.
Kramar and Alim’s study challenges this conventional wisdom. By showing how P. polycephalum modifies its internal structure in response to food, they reveal a mechanobiological memory system that doesn’t rely on neural circuits.
Instead, it’s all about physics: changes in tube diameter are driven by internal pressure and the diffusion of a mysterious softening substance.
This finding isn’t just a novelty. It forces us to reconsider the very definition of memory and information processing.
If a simple slime mold can “remember” using only physical changes, what does that say about the potential for other non-neural systems to exhibit intelligence?
How the Slime Mold Memory Works
The study, published in Proceedings of the National Academy of Sciences USA, provides a detailed explanation of how P. polycephalum encodes memory.
When the organism encounters food, it releases a soluble substance that softens the gel-like walls of its tubes. This softening allows the tubes to expand under internal pressure, creating a physical record of the food’s location.
This mechanism is surprisingly efficient. The substance spreads through the organism’s network by flow and diffusion, ensuring that the memory signal reaches relevant areas.
The widened tubes then guide the organism’s future movements, even in the absence of food.
This process is akin to leaving breadcrumbs along a path, except the breadcrumbs are part of the organism itself.
While the exact nature of the softening substance remains unknown, its role is clear. By altering the organism’s physical structure, it encodes information in a way that is both durable and adaptable.
This memory system allows P. polycephalum to navigate its environment with remarkable efficiency, solving problems that would challenge even some animals.
Implications for Biology and Beyond
The implications of this research extend far beyond slime molds. The mechanism identified by Kramar and Alim could be a common feature of other “living flow networks,” such as the vascular systems of vertebrates.
If similar processes are at play in more complex organisms, it could reshape our understanding of how biological systems store and process information.
Moreover, the study has practical applications. The ability of slime molds to optimize networks has already inspired algorithms for routing and resource distribution.
By understanding the underlying mechanisms of slime mold memory, researchers could develop even more efficient solutions for challenges in fields like logistics, urban planning, and computer science.
Simon Garnier, a biologist at the New Jersey Institute of Technology, sees this as a significant step forward. “The researchers’ model provides a nice mechanistic explanation for how slime mold achieves this feat,” he says.
“It could lead to improved network optimization and routing algorithms, similar to those inspired by ant colonies.”
A New Frontier in Understanding Intelligence
The discovery that slime molds can encode memory through structural changes raises profound questions about the nature of intelligence.
Hans-Günther Döbereiner, a physicist at the University of Bremen, emphasizes the need for further research. “Future studies will need to examine molecular signaling, material properties, and flow patterns of the cellular fluid regulating its behavior,” he says.
This work also invites us to think differently about intelligence itself. If memory and problem-solving can arise from physical processes, it suggests that intelligence might not be exclusive to brains or even to living organisms.
Could similar principles be engineered in synthetic systems? Could robots or materials be designed to “remember” and adapt using physical changes alone?
As we explore these questions, slime molds will likely continue to surprise us. These unassuming organisms have already revolutionized our understanding of memory, optimization, and problem-solving. Who knows what other secrets they might hold?
Lessons from the Humble Slime Mold
Slime molds may lack brains, but they don’t lack brilliance. By physically encoding food locations in their tube networks, they demonstrate a form of memory that is both elegant and effective.
This discovery not only deepens our appreciation for these fascinating organisms but also opens up new avenues of research across biology, technology, and beyond.
So the next time you see a slime mold, don’t dismiss it as a simple blob. It’s a master problem-solver, a network optimizer, and a memory pioneer — all rolled into one.
