predictive coding and active inference karl friston, university college london
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Predictive coding and active inference Karl Friston, University College London. - PowerPoint PPT PresentationTRANSCRIPT
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How much about our interaction with and experience of our world can be deduced from basic principles? This talk reviews recent attempts to understand the self-organised behaviour of embodied agents, like ourselves, as satisfying basic imperatives for sustained exchanges with the environment. In brief, one simple driving force appears to explain many aspects of action and perception. This driving force is the minimisation of surprise or prediction error that in the context of perception corresponds to Bayes-optimal predictive coding. We will look at some of the phenomena that emerge from this principle; such as hierarchical message passing in the brain and the perceptual inference that ensues. I hope to illustrate the ensuing brain-like dynamics using models of bird songs that are based on autonomous dynamics. This provides a nice example of how dynamics can be exploited by the brain to represent and predict the sensorium that is in many instances generated by ourselves. I hope to conclude with an illustration that illustrates the tight relationship between communication and active inference about the behaviour of self and others.
Predictive coding and active inference Karl Friston, University College London
The anatomy of inferencepredictive codinggraphical modelscanonical microcircuits
Birdsongperceptual categorizationomission related responsessensory attenuationa birdsong duetOverview
Objects are always imagined as being present in the field of vision as would have to be there in order to produce the same impression on the nervous mechanism - von Helmholtz
Thomas BayesGeoffrey HintonRichard FeynmanThe Helmholtz machine and the Bayesian brainRichard Gregory
Hermann von Helmholtz Objects are always imagined as being present in the field of vision as would have to be there in order to produce the same impression on the nervous mechanism - von Helmholtz Richard Gregory
Hermann von Helmholtz sensory impressionsPlato: The Republic (514a-520a)
Bayesian filtering and predictive coding
changes in expectations are predicted changes and (prediction error) corrections
prediction error
Minimizing prediction error
Change sensationssensations predictionsPrediction errorChange predictionsActionPerception
A simple hierarchyGenerative models
whatwhereSensory fluctuations
Generative modelModel inversion (inference)A simple hierarchyDescendingpredictionsAscending prediction errorsFrom models to perception
Expectations:Predictions:Prediction errors:Predictive coding
Haeusler and Maass: Cereb. Cortex 2006;17:149-162Bastos et al: Neuron 2012; 76:695-711Canonical microcircuits for predictive coding
frontal eye fieldsgeniculatevisual cortexretinal inputponsoculomotor signals
Errors (superficial pyramidal cells)Expectations (deep pyramidal cells)Top-down or descending predictionsBottom-up or ascending prediction errorproprioceptive inputreflex arcPerception
David MumfordPredictive coding with reflexesAction
Interim summary
Hierarchical predictive coding is a neurobiological plausible scheme that the brain might use for (approximate) Bayesian inference about the causes of sensations
Predictive coding requires the dual encoding of expectations and errors, with reciprocal (neuronal) message passing
Much of the known neuroanatomy and neurophysiology of cortical architectures is consistent with the requisite message passing
It is the theory of the sensations of hearing to which the theory of music has to look for the foundation of its structure." (Helmholtz, 1877 p.4)
Helmholtz, H. (1877). On the Sensations of Tone as a Physiological Basis for the Theory of Music", Fourth German edition,; translated, revised, corrected with notes and additional appendix by Alexander J. Ellis. Reprint: New York, Dover Publications Inc.,1954
Hermann von Helmholtz The anatomy of inferencepredictive codinggraphical modelscanonical microcircuits
Birdsongperceptual categorizationomission related responsessensory attenuationa birdsong duetOverview
Generating bird songs with attractorsSyrinxHigher vocal centertime (sec)FrequencySonogram0.511.5
Hidden causesHidden states
102030405060-505101520prediction and error102030405060-505101520hidden statesDescending predictionsAscending prediction error102030405060-10-505101520causal statesPredictive coding and message passingstimulus0.20.40.60.82000250030003500400045005000time (seconds)
Perceptual categorization
Frequency (Hz)Song a
time (seconds)Song b
Song c
Sequences of sequences
Time (sec)Frequency (KHz)0.511.5
SyrinxHigher vocal centerSonogramArea X
omission and violation of predictionsStimulus but no perceptPercept but no stimulusFrequency (Hz)stimulus (sonogram)25003000350040004500Time (sec)Frequency (Hz)percept0.511.525003000350040004500500100015002000-100-50050100peristimulus time (ms)LFP (micro-volts)ERP (prediction error)without last syllableTime (sec)percept0.511.5500100015002000-100-50050100peristimulus time (ms)LFP (micro-volts)with omission
ThalamusArea X
Higher vocal centreHypoglossal Nucleus
Active inference: creating your own sensationsMotor commands (proprioceptive predictions)Corollary discharge(exteroceptive predictions)
Active inference and sensory attenuation
Active inference and sensory attenuationMirror neuron system
time (sec)Frequency (Hz)percept1234567250030003500400045005000012345678-50050100time (seconds)First level expectations (hidden states)012345678-40-20020406080time (seconds)Second level expectations (hidden states)
time (sec)Frequency (Hz)percept1234567250030003500400045005000012345678-50050100time (seconds)First level expectations (hidden states)012345678-40-20020406080time (seconds)Second level expectations (hidden states)Active inference and communication
"There is nothing in the nature of music itself to determine the pitch of the tonic of any composition...In short, the pitch of the tonic must be chosen so as to bring the compass of the tones of the piece within the compass of the executants, vocal or instrumental. (Helmholtz, 1877 p. 310)
Helmholtz, H. (1877). On the Sensations of Tone as a Physiological Basis for the Theory of Music", Fourth German edition,; translated, revised, corrected with notes and additional appendix by Alexander J. Ellis. Reprint: New York, Dover Publications Inc.,1954
Hermann von Helmholtz Thank you
And thanks to collaborators:
Rick AdamsAndre BastosSven BestmannHarriet BrownJean DaunizeauMark EdwardsXiaosi GuLee HarrisonStefan KiebelJames KilnerJrmie MattoutRosalyn MoranWill PennyLisa Quattrocki Knight Klaas Stephan
And colleagues:
Andy ClarkPeter DayanJrn DiedrichsenPaul FletcherPascal FriesGeoffrey HintonJames HopkinsJakob HohwyHenry KennedyPaul VerschureFlorentin Wrgtter
And many others