The graphical brain: belief propagation and active inference

K.J. Friston, T. Parr, B. de Vries

Research output: Contribution to journalArticleAcademicpeer-review

81 Citations (Scopus)
168 Downloads (Pure)

Abstract

This paper considers functional integration in the brain from a computational perspective. We ask what sort of neuronal message passing is mandated by active inference—and what implications this has for context-sensitive connectivity at microscopic and macroscopic levels. In particular, we formulate neuronal processing as belief propagation under deep generative models. Crucially, these models can entertain both discrete and continuous states, leading to distinct schemes for belief updating that play out on the same (neuronal) architecture. Technically, we use Forney (normal) factor graphs to elucidate the requisite message passing in terms of its form and scheduling. To accommodate mixed generative models (of discrete and continuous states), one also has to consider link nodes or factors that enable discrete and continuous representations to talk to each other. When mapping the implicit computational architecture onto neuronal connectivity, several interesting features emerge. For example, Bayesian model averaging and comparison, which link discrete and continuous states, may be implemented in thalamocortical loops. These and other considerations speak to a computational connectome that is inherently state dependent and self-organizing in ways that yield to a principled (variational) account. We conclude with simulations of reading that illustrate the implicit neuronal message passing, with a special focus on how discrete (semantic) representations inform, and are informed by, continuous (visual) sampling of the sensorium.

Original languageEnglish
Pages (from-to)381-414
Number of pages34
JournalNetwork Neuroscience
Volume1
Issue number4
DOIs
Publication statusPublished - 1 Dec 2017

Keywords

  • Bayesian
  • Belief propagation
  • Connectivity
  • Factor graphs
  • Free energy
  • Message passing
  • Neuronal

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