Cognition as least action: the Physarum Lagrangian

TL;DR

This paper models Physarum polycephalum's adaptive network formation as a least-action principle, demonstrating that its path optimization emerges from minimizing energy dissipation, aligning with experimental observations.

Contribution

It introduces a Lagrangian framework for Physarum's dynamics, revealing that its adaptive behavior follows a physics-based variational principle for optimal transport.

Findings

Reproduces experimentally observed conductance patterns

Shows Physarum minimizes energy dissipation in network formation

Validates the least-action principle as a foundation of Physarum's adaptation

Abstract

The slime mould Physarum polycephalum displays adaptive transport dynamics and network formation that have inspired its use as a model of biological computation. We develop a Lagrangian formulation of Physarum's adaptive dynamics on predefined graphs, showing that steady states arise as extrema of a least-action functional balancing metabolic dissipation and transport efficiency. The organism's apparent ability to find optimal paths between nutrient sources and sinks emerges from minimizing global energy dissipation under predefined boundary conditions that specify the problem to be solved. Applied to ring, tree, and lattice geometries, the framework accurately reproduces the optimal conductance and flux configurations observed experimentally. These results show that Physarum's problem-solving on constrained topologies follows a physics-based variational principle, revealing least-action dynamics as the foundation of its adaptive organization.