[Comp-neuro] Re: Review announcement

Aldo Faisal aaf23 at cam.ac.uk
Tue Jul 22 13:13:26 CEST 2008


> Haven't done this in a long time. But who says neurons are noisy?

I am much enjoying this discussion!
Whether the observed neuronal variability is due to true randomness
(i.e. noise) or something
that just looks like noise is indeed not knew.  However, what has
changed is that we can now -
from bottom-up - understand how randomness from molecular processes (I
assume here diffusion, chemical reactions, fluctuations in signalling
proteins confirmation are stochastic) influences electrical activity
of whole cell behaviour and how this can produce variability in
(cellular) behaviour accounting for much of the overall variability
[1].

While in a large neuron these microscopic noise sources are
negligible, their effects becomes quite  significant
in the miniaturized (and thus energy efficient) circuits of our
cortex. In fact noise sets a universal lower limit to the
size of function neurons that is matched by anatomical data across
species [2] and will produce
steadily increasing variability in propagating action potentials [3].
Thus, noise from molecular sources can have an impact in the highly
energy efficient and thus compact circuits
of our brains, setting lower limits to how precise we can encode
information. How to design (like an engineer) a brain's circuits is
thus a multi-factor trade-off problem...and to me quite fascinating.


[1] Faisal, A.A., Selen, L.P. & Wolpert, D.M.  (2008) "Noise in the
nervous system".
Nat. Rev. Neurosci. 9, 292–303

[2] Faisal,A.A., White,J.A. & Laughlin, S.B. (2005) "Ion channel noise
places limits to the miniaturization of the brain's wiring",
Curr Biol, Vol. 15(12), pp. 1143-1149

[3] Faisal, A.A. and Laughlin, S.B. (2007)  "Stochastic simulations on
the reliability of action potential propagation in thin axons", PLOS
Comp. Biol. 3(5):e79


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