W6 - Predictive Processing Flashcards
(103 cards)
What is the premise of the Theory of Predicative Processing (Fristen)?
- the brain only has indirect access to information from its environment
- We do not actively perceive reality as it is, we perceive the inputs from our senses, eg., Plato’s cave
- The brain must gather information from a noisy, complex and uncertain environment
- Process information and act based on information for continued survival
- To achieve this, the predictive processing framework suggest the brain functions as a hierarchical bayesian inference device
Why is predictive processing hierarchical?
Each part of the brain has a model about the inputs it expects to receive, organised in cortical hierarchy
brain regions processing sensory information mainly process low level isolated percepts of sensory inputs
while more frontal regions process complex syntheses of information from many sensory inputs, combined with memories, predictions and goals
Why is predictive processing baysian?
- beliefs are updated based on the the strength of the prior belief and the strength of new evidence
- e.g., you confidence in the original belief + new evidence + strength/precision of evidence = determines if you update your hypothesis
Example = Seeing a cat clearly with new evidence = cat
Seeing a cat in corner of eye + have a dog = might be a dog
Why does predictive processing have Inference device?
our brains can’t directly access the environment, so everything is done based on inferences based on our sensory inputs
Predictive processing must be done efficient, without spending all body’s finite energy, and can’t update continuously
What is the Metaphor: Zoom calls?
- zoom/call does NOT send through every pixel through the screen, and only transmits the pixels that changes, = maximises efficiency, saves energy
- If you stay very still, all the pixels will keep displaying as they were
It would take a lot of bandwidth energy to continuously update every pixel in a zoom call
When does PP model update its beliefs?
it ONLY UPDATES PREDICTIONS BASED ON ERRORS FROM SENSORY INFORMATION WHERE THE SENSORY INFORMATION WASN’T PREDICTED
If the model already knew the sensory input, it doesn’t update at all, maximises efficiency
What is a ‘surprise’?
the long term average of these prediction errors - brain tries to minimise
reading: non preferred outcomes
What is ‘free energy’?
its energy it uses associated with dealing with prediction errors
How long do prediction errors take?
about 50ms
What happens when predictions are incorrect and how is it evaluated?
- prediction errors are passed UP the cortical hierarchy via synaptic depolarisation, updating the predictive model
- In a hierarchical bayesian manner, predictions are updated depending on the top-down predicted PRECISION of the EVIDENCE for the error relative to the STRENGTH of the PRE-EXISTING belief/prediction
- This bayesian inference allows the higher region to decide whether to update the predictive model or not
What do Top down predictions do?
Top down predictions modulate strength of the prediction error AND direct precision of processing based on internally held goals,
What kinds of predictions are in the frontal lobe?
- More abstract models of a person’s interactions, abstract thought and planning are made by frontal regions
- Abstract predictions are transmitted to the posterior regions, to modulate the precision of prediction errors/synaptic gain for specific sensory information, like an attention function
What do posterior regions do?
Posterior regions process sensory information - when the model is incorrect, prediction errors from sensory regions pass up to the frontal regions
Does the brain does passively receive information? -
- NO -it receives information AND change the environment so the environment will produce new evidence/info that might be more aligned with our predictions and future state it wants to find itself in
What are the two types of inference the brain makes to align with its internal goals?
- Perceptual inference: Updates the predictive model based on new prediction errors
- Active inference = Use motor control functions to act, to attempt to allow future sensory inputs to be more aligned with predictions
*Designates actions to best lead to a desired future state
* minimise average prediction error
Why might active inference produce temporary in prediction error to minimise overall prediction error in the long term?
sometimes active inference might involve producing temporary increases in prediction error by seeking information in uncertain environments,
allowing updated trajectories towards desired states, rather than just missing short term prediction error
A reflex response from jumping back from touching a stove is an example of a…
Simple example of active inference, to match prediction that we are free from burning pain
Wanting to get a good grade, implementing sequences of action trajectories to update predictive models with info to pass your exams is a…
Complex example of active inference
What is the IMPLICATIONS OF PREDICTIVE PROCESSING regarding entropy?
By adhering to this driving force of trying to minimise long-term average prediction error by performing active inferences - the brain can continue to exist despite the tendency of the universe to learn towards entropy
Counter to law of entropy, we manage to continuously self-organise via performing predictive processing, causing active inference using energy to maintain order predicted in one’s own body
What happens if we don’t follow the prompts of the prediction errors coming in and implement new active inference policies to get into a better state of prediction?
you may find yourself in a state of complete environmental reality that doesn’t match our reality
EG., why trauma is so destructive
What does dynamical systems theory claim?
- That complex systems like humans pursuing limited sets of preferred / predicted states, are called attractors, “attracted to predictive states to allow us to continuously perceive evidence aligning with our current reality”
Inference is close to a theory of everything, evolution, consciousness and life = Foundation of what it means to be alive
What are preferred predicted states called?
attractors
HOW DID INFERENCE HAPPEN BEFORE INFERRERS EXISTED, IN AN ENTROPIC UNIVERSE?
Think - evolution
- Our brain system has evolved to continues update its predictive model from the environment to make active inferences and verify its predictions
- Brains that were not effective at doing predictive processing DID NOT SURVIVE and pass on code without predictive processing
What is an organism’s survive based on?
- Choice organism that are more likely to occupy their ecological niche
adaptive fitness is thus the likelihood of finding a phenotype in its environment - An organism’s survival is about the likelihood of being a good model for its niche, e.g., different birds on Galapagos Islands