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A Free Energy Principle for Biological Systems
1The Wellcome Trust Centre for Neuroimaging, Institute of Neurology, Queen Square, London, WC1N 3BG, UK; k.friston@ucl.ac.uk ; Tel.: +44 (0)203 448 4347/
Entropy (Basel, Switzerland)
|December 4, 2012
Summary
This study introduces a free energy principle to explain how biological systems resist disorder. It uses nonlinear Fokker-Planck equations and information theory to show how systems maintain order by minimizing free energy.
Area of Science:
- Theoretical Biology
- Statistical Physics
- Dynamical Systems Theory
Background:
- Biological systems exhibit self-organization and resist natural decay towards disorder.
- Understanding the principles governing this self-organization is crucial for various biological disciplines.
- Existing models often involve complex dynamics and causality.
Purpose of the Study:
- To propose a unified free energy principle explaining biological order.
- To link principles of self-organization with information theory.
- To provide a framework applicable beyond neuroscience.
Main Methods:
- Utilizing nonlinear Fokker-Planck equations to model random dynamical systems.
- Separating system states into external (fluctuating) and internal (deterministic) components.
- Applying a principle of least action based on variational free energy.
Main Results:
- Demonstrated a formal equivalence between variational free energy minimization and the information bottleneck method.
- Showed that minimizing free energy leads to reduced Shannon entropy in external states.
- Established a framework for understanding how systems maintain a limited set of states.
Conclusions:
- The proposed free energy principle offers a parsimonious explanation for biological order.
- The approach has proven effective in neuroscience and shows potential in molecular and evolutionary biology.
- Variational free energy minimization provides a powerful, generalizable framework for biological self-organization.
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