Untangling cross-frequency coupling in neuroscience

http://biorxiv.org/content/early/2014/08/25/005926

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Statistical mechanics of multistable perception

 
 
The stochastic dynamics of multistable perception poses an enduring challenge to our understanding of neural signal processing in the brain. We show that the emergence of perception switching and stability can be understood using principles of probabilistic Bayesian inference where the prior temporal expectations are matched to a scale-free power spectrum, characteristic of fluctuations in the natural environment. The optimal percept dynamics are inferred by an exact mapping of the statistical estimation problem to the motion of a dissipative quantum particle in a multi-well potential. In the bistable case the problem is further mapped to a long-ranged Ising model. Optimal inference in the presence of a 1/f noise prior leads to critical dynamics, exhibiting a dynamical phase transition from unstable perception to stable perception, as demonstrated in recent experiments. The effect of stimulus fluctuations and perception bias is also discussed.

PPPR: Electron spin changes during general anesthesia in Drosophila

I’m going to try something I’ve never done on this blog before. I’m posting a paper that has already been published. I made some negative comments about this work on Twitter and the first author Luca Turin (@lucaturin) invited me to comment formally in a letter to PNAS. I think it would be more interesting to get a discussion going that involves other people. Maybe I’m being unreasonable? As far as I know, PNAS has no facility for comments on its website, so let’s comment on it here. I for one would find it easier to elaborate on my viewpoint outside of 140 characters. Anyone who is interested should read the paper at the link provided below and add a comment to this post.

http://www.pnas.org/content/early/2014/08/06/1404387111.long

Luca Turin, Efthimios M. C. Skoulakis, and Andrew P. Horsfield
 
We show that the general anesthetics xenon, sulfur hexafluoride,
nitrous oxide, and chloroform cause rapid increases of different
magnitude and time course in the electron spin content of
Drosophila. With the exception of CHCl3, these changes are reversible.
Anesthetic-resistant mutant strains of Drosophila exhibit a different
pattern of spin responses to anesthetic. In two such mutants,
the spin response to CHCl3 is absent. We propose that these spin
changes are caused by perturbation of the electronic structure of
proteins by general anesthetics. Using density functional theory,
we show that general anesthetics perturb and extend the highest
occupied molecular orbital of a nine-residue α -helix. The calculated
perturbations are qualitatively in accord with the Meyer–Overton
relationship and some of its exceptions. We conclude that there
may be a connection between spin, electron currents in cells, and
the functioning of the nervous system