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Filtering the mind and approximating the world: the free energy principle in sensory systems.
thesisposted on 28.02.2017, 00:13 by Paton, Bryan Kerry
The Free Energy Principle is a broad organising framework for biological life based on the assumption that organisms seek the continuation of their own existence in the face of environmental perturbations. Organisms are finite entities with indirect access to their environment and only direct access to the outputs of their sensory epithelia. Given such constraints, organisms can solve this dilemma by developing and maintaining a generative model of the causes of sensory states (hidden environmental states). This process is aimed at minimising the discrepancy, the free energy between predictions born from the model and incoming sensory data by means of a gradient descent process, generalised filtering. By either adjusting the parameters of this model, or its own sensory input through locomotion perception and action are realised. The very broadness of the Free Energy Principle predicts that neural mechanisms whilst constrained in terms of their general function are free to adopt many different specific forms. This thesis is concerned with how the Free Energy Principle might be realised in action and perception generally and in four specific cases. Under the banner of action, two behavioural rubber hand illusion studies examine how bodily perception can be easily fooled and manipulated and how this influences subsequent action. The first study focuses on the development of a new rubber hand illusion paradigm. The second study compares a sample of autistic spectrum disorder patients with healthy controls in changes in body perception in the context of action. Under the banner of perception, two electrophysiological studies, one based on the auditory mismatch negativity and the other on continuous flash suppression in vision are focused on how the Free Energy principle is applied in these cases. The stochastic mismatch negativity developed in the thesis matches the kind of problem that an organism must solve; determine the true or hidden states of the environment given otherwise noisy input. The continuous flash suppression study, emphasises the role of model competition in ambiguous perceptual situations. Both studies focus on electrophysiological correlates of free energy minimisation. The conclusion is that consideration of the Free Energy Principle and generalised filtering in particular provides a promising and comprehensive alternative to more traditional accounts of neural function that is ultimately applicable across a broad range of scientific disciplines.