Slide 1
How much about our interactions 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 (that suppresses exteroceptive
prediction errors) and in the context of action reduces to
classical motor reflexes (that suppress proprioceptive prediction
errors). We will look at some of the implications for the anatomy
of this active inference, in terms of large-scale anatomical graphs
and canonical microcircuits. Specifically, we will look at the
functional and anatomical asymmetries in (extrinsic and intrinsic)
connections and their implications for spectral responses.Canonical
circuits for predictive codingKarl Friston, University College
London
Overview
The free-energy principleaction and perceptionpredictive coding
with reflexes
The anatomy of inferencegraphical modelscanonical
microcircuits
Functional asymmetriesextrinsic connectionsintrinsic
connections
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 FeynmanFrom the Helmholtz
machine to the Bayesian brain and self-organizationRichard
Gregory
Hermann von Helmholtz Ross Ashby
Minimizing prediction error
Change sensationssensations predictionsPrediction errorChange
predictionsActionPerception
Prior distributionPosterior distributionLikelihood
distributiontemperature
Prediction errors the Bayesian thermostat
20406080100120
Perception
Action
Overview
The free-energy principleaction and perceptionpredictive coding
with reflexes
The anatomy of inferencegraphical modelscanonical
microcircuits
Functional asymmetriesextrinsic connectionsintrinsic
connections
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 backward predictionsBottom-up or forward
prediction errorproprioceptive inputreflex arcPerception
David MumfordPredictive coding with reflexesAction
Overview
The free-energy principleaction and perceptionpredictive coding
with reflexes
The anatomy of inferencegraphical modelscanonical
microcircuits
Functional asymmetriesextrinsic connectionsintrinsic
connections
superficialdeep
Errors (superficial pyramidal cells)Expectations (deep pyramidal
cells)
02040608010012000.050.10.150.20.250.3020406080100120012frequency
(Hz)
02040608010002468101214spectral powerForward transfer
function0204060801000123456frequency (Hz)spectral powerBackward
transfer function
Andre BastosV4V1
Errors (superficial pyramidal cells)Expectations (deep pyramidal
cells)
Linear or driving connectionsNonlinear or modulatory
connectionssuperficialdeep
NMDA receptor density
020406080100120012frequency (Hz)
Errors (superficial pyramidal cells)Expectations (deep pyramidal
cells)
superficialdeep
Nonlinear (cross frequency) coupling020406080100120012frequency
(Hz)
02040608010012000.050.10.150.20.250.3
STNM1STNM1
On dopamineOff dopamine
M1STN
M1STN
Bernadette Van WijkSummary
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
In particular, the functional asymmetries and laminar
specificity of intrinsic and extrinsic connections provide a formal
perspective on spectral asymmetries and cross frequency coupling in
the brain.Thank you
And thanks to collaborators:
Rick AdamsAndre BastosSven BestmannHarriet BrownCC ChenPascal
FriesLee HarrisonStefan KiebelJames KilnerAndre MarreirosJrmie
MattoutRosalyn MoranWill PennyKlaas StephanBernadette Van Wijk
And many others