Study reveals mechanical basis of decision-making in slime molds
Researchers have found that the brainless slime mold Physarum polycephalum makes escape decisions through a gradual mechanical reorganization of internal peristaltic contraction waves rather than any centralized control. Confined by blue-light barriers into geometric shapes, the organism probes all directions before eventually aligning its dominant contraction mode along the shape's longest axis, where pressure builds most efficiently to drive a mass escape. The findings illuminate how decentralized biological systems can produce adaptive, apparently 'intelligent' behavior through purely physical fluid-dynamics principles.
A study published in PRX Life by researchers at the Technical University of Munich and collaborators in the United States reveals the mechanical basis of decision-making in Physarum polycephalum, a single-celled slime mold with no brain or nervous system. Using barriers of 470 nm blue light shaped into polygons — triangles, squares, hexagons, and other forms — the team trapped starved slime molds and observed their escape behavior over periods of roughly 6 to 18 hours. Time-lapse imaging showed the organism extending small protrusions in nearly all directions during an exploratory phase, while phase-of-contraction maps revealed traveling peristaltic waves continuously shifting orientation across the organism's body. Rather than immediately selecting the optimal escape route, the mold cycled through multiple dominant contraction modes before gradually settling on the one aligned with the shape's longest axis — the configuration that allows the greatest pressure buildup and mass transport. Crucially, the escape always occurred along this longest axis regardless of the polygon's specific geometry, suggesting the trap shape itself passively selects the mechanically optimal mode. The researchers conclude that harsh environmental confinement, rather than any internal computation, triggers this optimization by forcing prolonged reorganization of internal flow patterns. The work offers a concrete mechanical framework for understanding how non-neuronal organisms process environmental constraints to generate adaptive behavior.
What's missing
The study does not address whether the time required for contraction-mode reorganization scales with organism size or starvation duration, nor whether the same longest-axis escape rule holds in three-dimensional or non-planar confinement geometries. It also remains open whether other slime mold species or other non-neuronal organisms exhibit analogous mechanical decision-making mechanisms.
What different sources said
- ScienceAlertCenter
Physicists Discover How Slime Mold 'Makes Decisions' Without a Brain
- arXiv physicsCenter
Decision-making in light-trapped slime molds involves active mechanical processes
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