[Comp-neuro] Review announcement

jim bower bower at uthscsa.edu
Tue Jul 22 12:46:25 CEST 2008


One other general point about oscillations. Years ago a "neural network" engineer from MIT gave a talk at the Snowbird meeting, I think the first - in his talk he that, connected at random only 1 percent of networks didn't oscillate intrinsically, and he proposed to find those networks as they were clearly the only ones that were useful. 

Interesting idea but dead wrong. Everything in biology oscillates, in fact everything in the natural world does. Engineers fear oscillations because they don't know how to control them. The nervous system uses them to its own purposes. In fact, my guess is that this is one of the sources of its efficiency. 

Last point with respect to your car, the quality of the engineer must be based on the performance of what it has built. So last last question, does anyone know something whose perfomance is more extraordianary then the brain of a fly?  Or a slug?  

I don't think so

Jim


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-----Original Message-----
From: "Hans A. Braun" <braun at staff.uni-marburg.de>

Date: Tue, 22 Jul 2008 11:32:54 
To: <bower at uthscsa.edu>; Nathan Urban<nurban at cmu.edu>; <comp-neuro-bounces at neuroinf.org>; <comp-neuro at neuroinf.org>
Subject: Re: [Comp-neuro] Review announcement


Hi Jim,



nice to hear from you with an interesting question. Here is a question back:

Who says that the biological coding scheme is optimised in a way as
engineers would do?



I have been educated as an engineer. Thereby, I specifically have learnt how
handle, if it cannot be avoided, such detrimental system properties like
noise, nonlinearities and time delays because these can lead to
unpredictable system behavior, including undesired oscillation and chaos –
what regularly can be seen in all kind of biological systems. If something
similar would happen in a car or an airplane, the responsible engineer,
deservedly, would immediately be fired.



Could it be that the engineer in evolution has used a principally different
strategy?

What was/is his/her goal?

Who knows or who is interested to find the answer?

- or a more appropriate question ;-) ?



Coming back to the original "noise" question: During all the years as
experimental physiologist I have got hundreds of hours recordings of impulse
sequences from different neurons – and all look more or less noisy -
whatever it means.



Best wishes

Hans Braun



PS: if you are interested, here are two references to our work (an actual
and an earlier paper):



Finke C, Vollmer J, Postnova S, Braun HA (2008) Propagation effects of
current and conductance noise in a model neuron with subthreshold
oscillations. Mathematical Biosciences doi:10.1016/j.mbs.2008.03.007

Braun HA, Wissing H, Schäfer K, Hirsch MC (1994). Oscillation and noise
determine signal transduction in shark multimodal sensory cells. Nature 367:
270-273.



The first one is a mathematical/computational approach which has very
recently been published, so far only as online version.

The second reference is to a much earlier experimental paper which
demonstrates how the evolutionary engineer might have used oscillations and
noise to achieve a particular sensitivity. This strategy, for whatever
reasons, was only realized for sensory encoding in some evolutionary very
old animals like sharks.

Dr. Hans A. Braun, Institute of Physiology, Deutschhausstr. 2, D-35037
Marburg, Germany.
Tel: +49 (0)6421-286 23 05, FAX: +49 (0)6421-286 6967, E-mail:
braun at staff.uni-marburg.de
URL: http://www.uni-marburg.de/physiology/braun and  http://www.clabs.de
see also: http://www.BioSim-Network.net

----- Original Message -----
From: "jim bower" <bower at uthscsa.edu>
To: "Nathan Urban" <nurban at cmu.edu>; <comp-neuro-bounces at neuroinf.org>;
<comp-neuro at neuroinf.org>
Sent: Friday, July 18, 2008 3:56 PM
Subject: Re: [Comp-neuro] Review announcement


> Haven't done this in a long time. But who says neurons are noisy?
>
> From the point of view of information theory, why isn't the apperance of
noise expected in a highly optimized coding scheme?  And why isn't synchrony
to be avoided as redundency. Engineers avoid it, why shouldn't evolution.
>
> Just curious.
>
> Jim bower
> Sent via BlackBerry by AT&T
>
> -----Original Message-----
> From: Nathan Urban <nurban at cmu.edu>
>
> Date: Fri, 18 Jul 2008 08:41:22
> To: <comp-neuro at neuroinf.org>
> Subject: [Comp-neuro] Review announcement
>
>
> Review announcement
>
> This review describes a constructive role for noise in synchronizing
> populations of neurons and should be of interest to computaional
> neurosciuentists.
>
>
> Trends Neurosci. 2008 Jul 4. [Epub ahead of print]
>     Reliability, synchrony and noise.
>     Ermentrout GB, Galán RF, Urban NN.
>
> The brain is noisy. Neurons receive tens of thousands of highly
> fluctuating inputs and generate spike trains that appear highly
> irregular. Much of this activity is spontaneous - uncoupled to overt
> stimuli or motor outputs - leading to questions about the functional
> impact of this noise. Although noise is most often thought of as
> disrupting patterned activity and interfering with the encoding of
> stimuli, recent theoretical and experimental work has shown that noise
> can play a constructive role - leading to increased reliability or
> regularity of neuronal firing in single neurons and across populations.
> These results raise fundamental questions about how noise can influence
> neural function and computation.
>
>     PMID: 18603311 [PubMed - as supplied by publisher]
>
>
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T0V-4SXC918-1&_us
er=525223&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000026389&_versio
n=1&_urlVersion=0&_userid=525223&md5=22a86291fe13cd59541d841f692f24a2
> _______________________________________________
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