[Comp-neuro] Hilbert's questions

Randall O'Reilly randy.oreilly at colorado.edu
Tue Aug 12 20:24:07 CEST 2008


On Aug 12, 2008, at 11:57 AM, james bower wrote:

> "someone like me"  hmmm

I'm just saying, you are evidently a man of strong opinions.. ;)

> First, I follow the hippocampal literature quite closely -- given my  
> 25 years of research in olfaction -- and actually have always been  
> amassed at how little the hippocampal learning guys even know about  
> olfaction -- (Howard Eichenbaum being the rare exception), given it  
> is likely that the hippocampus evolved out of the olfactory system
>
> Second, 'accounting for the data' or even 'making predictions' is  
> not enough - As I have pointed out on this list Ptolomy is one of  
> the most successful models in history by those standards.
>

I think in many ways the field would be lucky to have a Ptolomy-level  
model!  You can't get to the "truth" in one step.  It is an iterative  
process and the truth is a very graded entity.  At a broad scale,  
there were many things right about Ptolomy's theory: he identified the  
relevant entities, accurately described their motions to some degree  
of approximation, used a formal, falsifiable framework, etc.  Once the  
problem is so well identified and characterized, then it provides the  
basis for further refinement and improvement of the theories (assuming  
people don't get overly attached to the original theory, which of  
course is a major, but separable, problem).

In the case of the brain, there are so many more rich sources of data  
than with planetary motion -- it is a much higher dimensional space --  
that it is probably much harder to have a "false" but successful  
theory such as Ptolomy's.  In this sense, the remarkable coherence  
between the biological and behavioral levels of analysis in the  
hippocampal domain, together with the predictive validity of the  
model, merits the "solved problem" (in quotes still -- I am being a  
bit provocative) status in my opinion.  Cheers,

- Randy

> Third, to even success that the hippocampus is largely a solved  
> problem more than manifests the concerns I have
>
> Jim
>
>
>
>
> On Aug 12, 2008, at 12:51 PM, Randall O'Reilly wrote:
>
>> I wouldn't expect to convince someone like you, but perhaps if you  
>> actually read the papers on this particular topic, you would see  
>> that the models can account for a huge range of biological and  
>> behavioral data, and critically make predictions that are being  
>> tested and validated.  Not all ideas are wrong.  Just the wrong ones.
>>
>> - Randy
>>
>> On Aug 12, 2008, at 11:44 AM, james bower wrote:
>>
>>> Wonderful what can be done with selective attention to detail,  
>>> overarching principles, and preconceived notions.
>>>
>>> "the hippocampus is essentially a solved problem" speaks for itself.
>>>
>>> so where the 'laws' of planetary motion, for about 1700 years.
>>>
>>> There is no doubt, that course (what it does) to fine (how it does  
>>> it) science is very efficient -- problem is, the course tends to  
>>> impose on the fine.
>>>
>>> Aspects of cognitive neuroscience may be the best examples,  
>>> perhaps in the history of science, of the danger of overarching  
>>> ideas, in the presence of non-structural models.
>>>
>>>
>>> Jim Bower
>>>
>>>
>>>
>>> On Aug 12, 2008, at 12:19 PM, Randall O'Reilly wrote:
>>>
>>>> There has been a remarkable absence of consideration for the  
>>>> functional level of the brain: i.e., the huge field of cognitive  
>>>> neuroscience, in this discussion and in the field of  
>>>> computational neuroscience in general.  There is no way you are  
>>>> going to figure out something as complex as the brain using a  
>>>> purely bottom-up strategy.  If you look at the work in  
>>>> computational *cognitive* neuroscience, where the behavioral  
>>>> level of analysis is taken seriously, the picture is much less  
>>>> bleak than the assessments provided here.  There are many models  
>>>> that relate the biological properties of neurons and brain areas  
>>>> to cognitive functions associated with those brain areas, and do  
>>>> a very good job of capturing a large proportion of the variance  
>>>> of both levels.
>>>>
>>>> For example, the hippocampus is essentially a "solved problem" in  
>>>> terms of the general framework for how its biological properties  
>>>> enable its well established role in memory.  Recent work by  
>>>> Tonagawa's group and several others have verified the predictions  
>>>> from a number of generally convergent computational models,  
>>>> regarding the specific roles of areas CA3, DG, CA1, etc.  By  
>>>> capturing the most global, high-level properties of the system  
>>>> first, across both behavior and biology, these models provide a  
>>>> framework within which more detailed questions and models can be  
>>>> developed.
>>>>
>>>> In almost every domain, a hierarchical coarse-to-fine strategy is  
>>>> the most efficient way to understand something.  First you figure  
>>>> out the most basic properties of the system, and then you fill in  
>>>> the details.  Some would argue that this is not possible in the  
>>>> brain, but I think the existing work already refutes that  
>>>> argument.  People who remain fixated on individual neurons and  
>>>> synapses may not appreciate this, and regard the system as a huge  
>>>> unsolved puzzle, but this is just because they are so zoomed in  
>>>> on the details that they are missing the big picture.  The big  
>>>> picture is filling in quite rapidly.  There are similarly  
>>>> successful models for prefrontal cortex, basal ganglia, and  
>>>> sensory neocortex, etc.
>>>>
>>>> Taken together these models strongly suggest that, to understand  
>>>> how the system actually functions, you don't need to simulate  
>>>> every last detail of a neuron, nor its connectivity.  Certain  
>>>> details are rather important (e.g., inhibition in the hippocampus  
>>>> is critical for establishing a sparse distributed representation,  
>>>> which minimizes interference and enables episodic memory, place  
>>>> cells, etc), but in general a fairly simple "integrate and fire"  
>>>> model of the neuron is sufficient to capture a large portion of  
>>>> the functional variance of what the brain actually does.
>>>>
>>>> Of course, I can't "prove" any of these assertions to the  
>>>> satisfaction of all skeptics, and I'm rather an optimist overall,  
>>>> but I think this field is definitely missing out on the big  
>>>> picture.  Certainly there is a huge amount still unknown, but if  
>>>> you squint your eyes just right, I think the picture is filling  
>>>> in quite nicely..
>>>>
>>>> - Randy
>>>>
>>>> On Aug 12, 2008, at 9:47 AM, james bower wrote:
>>>>
>>>>> 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
>>>>> 8403 Floyd Curl Drive
>>>>> San Antonio Texas  78284-6240
>>>>>
>>>>> Main Number:  210- 567-8100
>>>>> Fax: 210 567-8152
>>>>> Mobile:  210-382-0553
>>>>>
>>>>> CONFIDENTIAL NOTICE:
>>>>> The contents of this email and any attachments to it may be  
>>>>> privileged or
>>>>> contain privileged and confidential information. This  
>>>>> information is only
>>>>> for the viewing or use of the intended recipient. If you have  
>>>>> received this
>>>>> e-mail in error or are not the intended recipient, you are  
>>>>> hereby notified
>>>>> that any disclosure, copying, distribution or use of, or the  
>>>>> taking of any
>>>>> action in reliance upon, any of the information contained in  
>>>>> this e-mail, or
>>>>> any of the attachments to this e-mail, is strictly prohibited  
>>>>> and that this
>>>>> e-mail and all of the attachments to this e-mail, if any, must be
>>>>> immediately returned to the sender or destroyed and, in either  
>>>>> case, this
>>>>> e-mail and all attachments to this e-mail must be immediately  
>>>>> deleted from
>>>>> your computer without making any copies hereof and any and all  
>>>>> hard copies
>>>>> made must be destroyed. If you have received this e-mail in  
>>>>> error, please
>>>>> notify the sender by e-mail immediately.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Comp-neuro mailing list
>>>>> Comp-neuro at neuroinf.org
>>>>> http://www.neuroinf.org/mailman/listinfo/comp-neuro
>>>>
>>>
>>>
>>>
>>>
>>> ==================================
>>>
>>> Dr. James M. Bower Ph.D.
>>>
>>> Professor of Computational Neuroscience
>>>
>>> Research Imaging Center
>>> University of Texas Health Science Center -
>>> -  San Antonio
>>> 8403 Floyd Curl Drive
>>> San Antonio Texas  78284-6240
>>>
>>> Main Number:  210- 567-8100
>>> Fax: 210 567-8152
>>> Mobile:  210-382-0553
>>>
>>> CONFIDENTIAL NOTICE:
>>> The contents of this email and any attachments to it may be  
>>> privileged or
>>> contain privileged and confidential information. This information  
>>> is only
>>> for the viewing or use of the intended recipient. If you have  
>>> received this
>>> e-mail in error or are not the intended recipient, you are hereby  
>>> notified
>>> that any disclosure, copying, distribution or use of, or the  
>>> taking of any
>>> action in reliance upon, any of the information contained in this  
>>> e-mail, or
>>> any of the attachments to this e-mail, is strictly prohibited and  
>>> that this
>>> e-mail and all of the attachments to this e-mail, if any, must be
>>> immediately returned to the sender or destroyed and, in either  
>>> case, this
>>> e-mail and all attachments to this e-mail must be immediately  
>>> deleted from
>>> your computer without making any copies hereof and any and all  
>>> hard copies
>>> made must be destroyed. If you have received this e-mail in error,  
>>> please
>>> notify the sender by e-mail immediately.
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>
>
>
>
>
> ==================================
>
> Dr. James M. Bower Ph.D.
>
> Professor of Computational Neuroscience
>
> Research Imaging Center
> University of Texas Health Science Center -
> -  San Antonio
> 8403 Floyd Curl Drive
> San Antonio Texas  78284-6240
>
> Main Number:  210- 567-8100
> Fax: 210 567-8152
> Mobile:  210-382-0553
>
> CONFIDENTIAL NOTICE:
> The contents of this email and any attachments to it may be  
> privileged or
> contain privileged and confidential information. This information is  
> only
> for the viewing or use of the intended recipient. If you have  
> received this
> e-mail in error or are not the intended recipient, you are hereby  
> notified
> that any disclosure, copying, distribution or use of, or the taking  
> of any
> action in reliance upon, any of the information contained in this e- 
> mail, or
> any of the attachments to this e-mail, is strictly prohibited and  
> that this
> e-mail and all of the attachments to this e-mail, if any, must be
> immediately returned to the sender or destroyed and, in either case,  
> this
> e-mail and all attachments to this e-mail must be immediately  
> deleted from
> your computer without making any copies hereof and any and all hard  
> copies
> made must be destroyed. If you have received this e-mail in error,  
> please
> notify the sender by e-mail immediately.
>
>
>
>
>
>
>



More information about the Comp-neuro mailing list