[Comp-neuro] Hilbert's questions

james bower bower at uthscsa.edu
Tue Aug 12 17:47:11 CEST 2008


I would say for sure that individual neurons are communicating -- just  
that communication is not dependent on any individual neuron (in  
mammals), nor can one understand what they are communicating  
independent of the population - a nice enigma.

With respect to wiring - 'we' believe that nervous systems represent  
what they know in their wiring -- 'we' also believe that the  
modification of wiring takes place at the level of individual neurons  
(and even synapses).  So for didactic purposes:


1) does the function of an individual brain depend on the detailed  
wiring of that brain (likely)
2) can we therefore understand how brains function in general, by  
working on multiple individuals let alone multiple species
3) in other words, what level of wiring specification do we need?

and do we have the patience?

Speaking of grubby, now probably mostly lost in history, the first  
''realistic network" modeling effort I ever saw presented was of the  
sea slug tritonia, by an engineer (MIT) turned serious  
experimentalist, Peter Getting - Neuroscience 1981, I think.

Peter Getting had originally taken a faculty position at Stanford,  
and, on the assumption that wiring was everything, set about trying to  
understand the connections between the few (I think 6) types of  
motoneurons that control the swimming (if you want to call it that) of  
Tritonia.  Problem was that after his 6 year junior faculty  
appointment, he had only completed characterizing 3 of the 6 (as I  
remember) sets of connections.  This was not deemed reasonable  
progress, he was denied tenure and ended up taking a position in Iowa,  
where he steadfastly continued to complete the circuitry.  He did, and  
presented the results at the neuroscience meeting -- and I remember  
being astounded.  Peter would have actually been a major part of the  
first course in woods hole, had he not had a massive stroke while  
running (which he did many miles per day), ending up incapacitated.

However, for sure, we now know from invertebrate systems that the  
individual connections of individual neurons within an individual  
matter --

So -- if one believes in the importance of wiring -- shouldn't we all  
be working in invertebrate preparations?

Not an entirely rhetorical question -- it is clear from the history of  
science in general and physics in particular that picking the right  
problem is a key to progress.  Thus, Newton 'discovered' the inverse  
square law by examining the (nearly) circular orbit of the moon around  
the earth, for which he also had much better distance data, rather  
than looking at the sexier elliptical movements of the planets around  
the sun.

Maybe we should give up on cerebral cortex for several hundred years  
and all study tritonia instead.


Jim



On Aug 12, 2008, at 10:08 AM, Bill Lytton wrote:

>
>> grandest level it seems to me there is only one question: "What is  
>> each neuron communicating,
>> and how is the message encoded."
>
> I thought it was noted in recent discourse that the answer is  
> nothing and not? -- ie
> populations are needed.
>
>> That said, it could be an interesting exercise to come up with a  
>> list of the current Top Ten
>> Topics attracting the attention of
>
> Personally I would echo Martin and Douglas in their many papers  
> (from which I recommend Neuron
> 2007 56:226-238 for its broad scope) that we need to know how it is  
> wired where 'it' may be
> neocortex, thalamus, olfactory cortex or even bug whateveritis-ex.
>
> Framed computationally this could involve wiring exploration (which  
> we are doing lately) or
> development algorithms or new Hebb variants.  Of course, without the  
> accompanying
> physiological/anatomical exploration this will be meaningless.
>
> Admittedly this is a rather low-level question without the grand  
> sweep of a Hilbert q. but
> then biology is often grubby (even literally) rather than ethereal.
>
> Bill
>
> -- 
> William W. Lytton, MD
> Professor of Physiology, Pharmacology, Biomedical Engineering,  
> Neurology
> State University of NY, Downstate Medical Center, Brooklyn, NY
> billl at neurosim.downstate.edu http://it.neurosim.downstate.edu/~billl
> ________________________________________________________________




==================================

Dr. James M. Bower Ph.D.

Professor of Computational Neuroscience

Research Imaging Center
University of Texas Health Science Center -
-  San Antonio
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