Cited by 1,156Embodied and Extended CognitionNeural dynamics and brain functionMemory and Neural Mechanisms

Active inference: a process theory

Open access
Friston, Karl, FitzGerald, Thomas, Rigoli, Francesco, Schwartenbeck, Philipp, Pezzulo, Giovanni·2017·Neural Computation

Abstract

This article describes a process theory based on active inference and belief propagation. Starting from the premise that all neuronal processing (and action selection) can be explained by maximizing Bayesian model evidence—or minimizing variational free energy—we ask whether neuronal responses can be described as a gradient descent on variational free energy. Using a standard (Markov decision process) generative model, we derive the neuronal dynamics implicit in this description and reproduce a remarkable range of well-characterized neuronal phenomena. These include repetition suppression, mismatch negativity, violation responses, place-cell activity, phase precession, theta sequences, theta-gamma coupling, evidence accumulation, race-to-bound dynamics, and transfer of dopamine responses. Furthermore, the (approximately Bayes’ optimal) behavior prescribed by these dynamics has a degree of face validity, providing a formal explanation for reward seeking, context learning, and epistemic foraging. Technically, the fact that a gradient descent appears to be a valid description of neuronal activity means that variational free energy is a Lyapunov function for neuronal dynamics, which therefore conform to Hamilton’s principle of least action.

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Crossref · 10.1162/neco_a_00912

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  • The perception-action cycle and active inference make evaluation emergent from the agent's ongoing interaction with the environment, arising either through optimization of information flow or through minimization of expected surprise.

    “The perception-action cycle (Tishby and Polani, 2010) and active inference (Friston et al., 2017) both make evaluation emergent from the agent's ongoing interaction with the environment, arising either through optimization of information flow or through minimization of expected surprise.”

    From Toward Enactive Artificial Intelligence (2026) · cites this paper as Friston et al., 2017

    Sections 2.2 and 2.8 describe a continuing perception–action cycle in which new observations inform the evaluation of policies. Section 2.3 says policies minimize expected free energy, not simply expected surprise; it also says epistemic value can maximize expected Bayesian surprise. The information-flow alternative is attached to the other citation, not this one. (LLM, conf=0.84)

    Experimental — accuracy not yet measured
  • The marginal likelihood term scores the plausibility of a particle pursuing a path and is usually interpreted in terms of expected loss and pragmatic affordance.

    “This marginal likelihood scores the plausibility of a particle pursuing this kind of path and is usually interpreted in terms of expected loss (i.e., negative expected reward or utility) [66, 63], and pragmatic affordance [153, 123].”

    From The free energy principle made simpler but not too simple (2023) · cites this paper as [123]

    Section 2.3 links the expected free energy of a policy to expected cost, utility, and pragmatic or extrinsic value, supporting the pragmatic interpretation. It does not describe a particle pursuing a path or say that a marginal-likelihood term scores the plausibility of that path; those specifics are not supported by this source. (LLM, conf=0.82)

    Experimental — accuracy not yet measured
  • The brain builds a generative model of the world, constantly explaining its observations (active inference).

    “A prevailing account of human perception is that the brain builds a generative model of the world, constantly explaining its observations (Friston et al., 2017), i.e. active inference.”

    From Object-Centric Scene Representations Using Active Inference (2024) · cites this paper as Friston et al., 2017

  • These beliefs are used to evaluate the expected free energy of allowable policies, from which actions can be selected.

    “These beliefs are then used to evaluate the expected free energy of allowable policies, from which actions can be selected [123, 124, 125].”

    From The free energy principle made simpler but not too simple (2023) · cites this paper as [123]

  • The conditional independencies among states implicit in partially observed Markov decision processes entail the functional forms for variational and expected free energies.

    “The conditional independencies among states implicit in partially observed Markov decision processes entail the above functional forms for variational and expected free energies [124, 123].”

    From The free energy principle made simpler but not too simple (2023) · cites this paper as [123]

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Research works printed but not linked: 1

  1. [63]63. Knutson, B., & Bossaerts, P. (2007). Neural antecedents of financial decisions. Journal of Neuroscience, 27(31), 8174-8177.

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Authors
Friston, K., FitzGerald, T., Rigoli, F., Schwartenbeck, P., & Pezzulo, G.
Affiliations
  • Wellcome Centre for Human Neuroimaging (GB)
  • National Research Council (IT)
Corresponding author
  • Friston, Karl
  • FitzGerald, Thomas
  • Rigoli, Francesco
  • Schwartenbeck, Philipp
  • Pezzulo, Giovanni
Venue
Neural Computation
Publisher
MIT Press
Published
2017-01
Volume
29
Issue
1
Pages
1-49
ISSN
  • 0899-7667 (ISSN-L)
  • 1530-888X
OpenAlex
W2552810632
Cited by
1,156
References
113
Citations by year
2026: 142 · 2025: 145 · 2024: 124 · 2023: 129 · 2022: 145 · 2021: 147 · 2020: 155 · 2019: 73 · 2018: 61 · 2017: 35
FWCI
35.50
Type
journal article
Language
en
Open access
Locations
  • Neural Computation (publishedVersion)
  • PubMed (publishedVersion)
  • City Research Online (City University London) (submittedVersion)
  • UEA Digital Repository (University of East Anglia) (submittedVersion)
  • UCL Discovery (University College London) (submittedVersion)
  • MPG.PuRe (Max Planck Society) (submittedVersion)
Funders
  • Wellcome Trust (088130/Z/09/Z)
  • Österreichischen Akademie der Wissenschaften
  • Universität Salzburg
Topics
  • Life Sciences › Neuroscience › Cognitive Neuroscience › Embodied and Extended Cognition
  • Life Sciences › Neuroscience › Cognitive Neuroscience › Neural dynamics and brain function
  • Life Sciences › Neuroscience › Cognitive Neuroscience › Memory and Neural Mechanisms
Keywords
active inference, variational free energy, marginal likelihood, gradient descent, neural dynamics, Markov decision process, repetition suppression, mismatch negativity, place cells, phase precession, theta sequences, theta-gamma coupling, evidence accumulation, dopamine, reward seeking, contextual learning, Lyapunov function, Hamilton's principle of least action, action selection

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