20100903 08:34:14 
 onepage paper arguing that Friston's freeenergy view may not be
complete. Some points made are
 the inversion operated assumes a generative model
 the use of surprise is defined using a frequentist approach not
informational
 one idea : from the frequentist measure one one can derive a conditional probability (a Xhi2 distribution) of the probability. Not very far to the idea of Sahani & Dayan of a double probabilistic distribution
 explore surprise or avoid it: Fiorillo makes here a confusion of time scales. On the long term (learning) one tends to avoid surprise, on the short term (coding) this implies one jumps one surprise.
 points to his PLoS one paper: Fiorillo, C. D. Towards a general theory of neural computation based on prediction by single neurons. PLoS ONE 3, e3298 (2008)
 once again, people love bipolarity: frequentists against probabilists, topdown vs. bottomup, neurocentric vs global. neurons, areas, brains, groups of brains just don't care and evolve. it is our description that can be multiple. does a single one ("unified theory") exists iun today's language? at least I am convinced that (over generations) neurons adapt to behavior not the inverse, thus that if one has to seek for an information measure, it is certainly not in a ion's channel dynamic only.
 the answer of Friston goes into that direction / correctly defines surprise / nice figure showing how one can learn "to be a Lorenz attractor" (certainly assuming a generative model of dynamics)
 the open question is rather "how is the freeenergy principle encoded in the brain's architecture and dynamics?"
reference

Christopher D. Fiorillo. A neurocentric approach to Bayesian inference, URL . Nature Reviews Neuroscience, 11(8):605, 2010
A primary function of the brain is to infer the state of the world in order to determine which motor behaviours will best promote adaptive fitness. Bayesian probability theory formally describes how rational inferences ought to be made, and it has been used with great success in recent years to explain a range of perceptual and sensorimotor phenomena1, 2, 3, 4, 5. .

Karl Friston. Is the freeenergy principle neurocentric?, URL . Nature Reviews Neuroscience, 11(8):605, 2010
Recently, a freeenergy formulation of brain function was reviewed in relation to several other neurobiological theories (The freeenergy principle: a unified brain theory? Nature Rev. Neurosci. 11, 127–138 (2010) .
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