Slide 1

Abstract

If we assume that neuronal activity encodes a probabilistic representation of the world that optimizes free-energy in a Bayesian fashion, then this optimization can be regarded as evidence accumulation or (generalized) predictive coding. Crucially, both predictions about the state of the world generating sensory data and the precision of (confidence in) those data have to be optimized. In other words, we have to make predictions (test hypotheses) about the content of thesensorium and predict our confidence in those hypotheses. I hope to demonstrate themetacognitiveaspect of thisinference using simulations ofaction observation and sensory attenuation- to illustratethe nature of active inferenceand promote discussion about itsrolein making inferences about self and others.The Bayesian brain, free energy and psychopathology Cambridge May 23rd 2013

Karl Friston

Active inference, predictive coding and precision

Precision and false inference

Simulations of :

Auditory perception (and omission related responses)Handwriting (and action observation)Smooth pursuit eye movements (under occlusion)Sensory attenuation (and the force matching illusion)

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

Change sensationssensations predictionsPrediction errorChange predictionsActionPerceptionAction and perception minimise surprise

Prior distributionPosterior distributionLikelihood distributiontemperature

Action as inference the Bayesian thermostat

20406080100120

Perception

Action

Expectations:Predictions:Prediction errors:

Generative modelModel inversion (inference)A simple hierarchy

DescendingpredictionsAscending prediction errorsFrom models to perception

frontal eye fieldsgeniculatevisual cortexretinal inputponsoculomotor signals

Prediction error (superficial pyramidal cells)Conditional predictions (deep pyramidal cells)Top-down or backward predictionsBottom-up or forward prediction errorproprioceptive inputreflex arcPerceptionVTA

David MumfordPredictive coding with reflexesAction

Attention

Prediction error can be reduced by changing predictions (perception)

Prediction error can be reduced by changing sensations (action)

Perception entails recurrent message passing in the brain to optimize predictions

Action fulfils descending predictions

+-Decompensation(trait abnormalities)Compensation (to psychotic state)Neuromodulatory failure (of sensory attenuation)Attenuated violation responsesLoss of perceptual GestaltSPEM abnormalitiesPsychomotor povertyResistance to illusionsHallucinationsDelusions

Generative process (and model)

SyrinxNeuronal hierarchy Time (sec)Frequency (KHz)sonogram0.511.5

Frequency (Hz)perceptprediction error

Model inversion500100015002000-6-4-20246810peristimulus time (ms)LFP (micro-volts)

Reduced precision at second level

Compensatory reduction of sensory precision

Omission related responses, MMN and hallucinosis

Prior distributiontemperatureAction as inference the Bayesian thermostat

20406080100120

Perception:

Action:

00.20.40.60.811.21.40.40.60.811.21.4actionposition (x)position (y)00.20.40.60.811.21.4observationposition (x)Heteroclinic cycle (central pattern generator)

Descendingproprioceptive predictions

retinal inputponsoculomotor signalsproprioceptive inputreflex arc

Angular position of target in intrinsic coordinatesAngular direction of gaze in extrinsic coordinatesAngular direction of target in extrinsic coordinates

timevisual channels

Generative processGenerative model

Smooth pursuit eye movements eye (reduced precision)50010001500200025003000-2-1012Angular positiondisplacement (degrees) 50010001500200025003000-20-1001020304050time (ms)velocity (degrees per second)Angular velocity eye target

Eye movements under occlusion and reduced precision1002003004005006007008009001000-2-1012target and oculomotor anglestime (ms)displacement (degrees) 1002003004005006007008009001000-30-20-100102030target and oculomotor velocitiestime (ms)velocity (degrees per second) eye (reduced precision) eye target

Paradoxical responses to violations

Sensory attenuation, illusions and agency

Generative processGenerative modelMaking your own sensations

18

motor reflex arcthalamussensorimotor cortexprefrontal cortex

ascending prediction errorsdescending modulationdescending predictionsdescending motor predictionsdescending sensory predictions19High sensory attenuation

51015202530-0.500.511.52prediction and errorTime (bins)51015202530-0.500.511.52hidden statesTime (bins)51015202530-0.500.51hidden causesTime (bins)51015202530-0.8-0.6-0.4-0.200.20.40.60.81Time (bins)perturbation and action

Self-made actsFailure of sensory attenuation51015202530-0.500.511.52prediction and errortime51015202530-0.500.511.52hidden statestime51015202530-0.500.51hidden causestime51015202530-0.8-0.6-0.4-0.200.20.40.60.81timeperturbation and actionand psychomotor poverty102030405060-0.500.511.52prediction and errorTime (bins)102030405060-0.500.511.52hidden statesTime (bins)102030405060-0.500.511.52hidden causesTime (bins)102030405060-0.500.511.52Time (bins)perturbation and action102030405060-0.500.511.52hidden statesForce matching illusion102030405060-0.500.511.52prediction and errorTime (bins)Time (bins)Sensory attenuation102030405060-0.500.511.5hidden causesTime (bins)102030405060-0.500.511.5Time (bins)perturbation and action

00.511.522.5300.511.522.53 External (target) forceSelf-generated(matched) forceExternal (target) forceSelf-generated(matched) forceSimulatedEmpirical (Shergill et al)

Failures of sensory attenuation, with compensatory increases in non-sensory precisionFailure of sensory attenuation and delusions of control?102030405060-0.500.511.522.533.5prediction and errorTime (bins)102030405060-0.500.511.522.533.5hidden statesTime (bins)102030405060-1-0.500.511.522.533.5hidden causesTime (bins)102030405060-0.500.511.522.533.5Time (bins)perturbation and action

+-Schizophrenia: (dopamine) failure of proprioceptive attenuation

Autism: (oxytocin) failure of interoceptive attenuation

Depression: (serotonin) failure of exteroceptive attenuation

Neuromodulatory failure (of sensory attenuation)Attenuated violation responsesLoss of perceptual GestaltSPEM abnormalitiesPsychomotor povertyResistance to illusionsHallucinationsDelusionsThank 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

Searching to test hypotheses life as an efficient experimentFree energy principleminimise uncertainty

Perception and Action: The optimisation of neuronal and neuromuscular activity to suppress prediction errors (or free-energy) based on generative models of sensory data.

Learning and attention: The optimisation of synaptic gain and efficacy over seconds to hours, to encode the precisions of prediction errors and causal structure in the sensorium. This entails suppression of free-energy over time.

Neurodevelopment: Model optimisation through activity-dependent pruning and maintenance of neuronal connections that are specified epigenetically

Evolution: Optimisation of the average free-energy (free-fitness) over time and individuals of a given class (e.g., conspecifics) by selective pressure on the epigenetic specification of their generative models.

Time-scaleFree-energy minimisation leading to