Slide 1
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