Fractal, yes! Chaos, not sure?

[bernard]

Hello all,

Some neurophysiologists are saying that brain exibits, as many "natural" constructions, a quite fractal assembly.

That is certainly true until an ultimate microscopic scale that ends with the tiny functionning elements composing the cell itself.

Neuron branching shows this in a perfect manner. It looks like a tree with branches, and smaller ones and smaller ones... But as a tree, the process ends with very little branches that escapes to easy investigation.

We are able to "probe" a neuron (some) and record the neural activity on large pathways. (red circles on the pictures).

http://www.somasimple.com/images/neuron/probing_01.jpg

[bernard]

The same researchers are confronted to a "noise" affair since they record a constant activity that "pollutes" and disturbs the "normal observation".

A while ago, it was said that chaos theory was initiating this "loudly" process.

I do not think so. We are only recording large sections of the neuron but are "irritated" by tiny branches. And it is well known that is leaves that make noise and leaves are often on small branches.

Does it mandatory say that chaos plays?

see the pink circles.

http://www.somasimple.com/images/neuron/noise_01.jpg

[Diane]

Bernard, Jänig has some points to make about methodology in Chapter three. I'll get it here eventually. :)

[Barrett Dorko]

Bernard,

It's my understanding that fractal shapes not only imply chaotic behavior within them but that it is the chaotic behavior that forms the fractal shape. This leads, clinically, to random and uncontrollable behavior within the organ that makes it appear mysterious. What we see eventually from most clinicians unaware of this process is a deep distrust of the neurologically irritated patient because they won't "behave" and they don't progress within a prescribed time frame for healing.

All of this results quite commonly in therapists saying to their colleagues, "I hate to see backs," and orthopedic surgeons saying to their secretaries, "You let another back in here and you're fired!"

All of this is explained in that picture at the top of this thread.

[bernard]

Barrett,

I think the problem comes with the scale notion.
I read something about this =>
http://plato.stanford.edu/entries/properties-emergent/

and I like the concept introduced by Laughlin (There is an interview in a French scientific revue).
A Different Universe: Reinventing Physics from the Bottom Down (http://www.amazon.fr/Different-Universe-Reinventing-Physics-Bottom/dp/0465038298)

I'll bring some images that disturbs the chaotic behaviour.

[bernard]

Each neuron comes in a "native" form.
The primitive branching doesn't exist yet. Then, a pruning process concurs to the image posted in the first post (http://www.somasimple.com/forums/showpost.php?p=28970&postcount=1). If the pruning exists, it may just tell us that it is the best solution?

http://www.somasimple.com/images/neuron/native.jpg

[bernard]

Each branch has its own growth's cone and it becomes understandable that the reduction process stands on a redundant but ephemeral stage.


http://www.somasimple.com/images/neuron/grow.jpg
http://www.somasimple.com/images/neurone/grow.jpg

[vajranata]

Bernard,
Great thread. Where are these images coming from? I'm not sure what I'm looking at here. Thanks.

[bernard]

The pictures come from these annual contests.
http://www.microscopyu.com/smallworld/gallery/index.html

The last picture is the terminal of an axon: It is called a growth cone and it is known that its attraction is chemical.
In the previous snapshot (the native neuron), an immature cell has many directions to throw its "filaments"/axons/dendrites.

A quick way is in the creation of many candidates at first and removing the weak ones once they are "tested".

[bernard]

J Physiol. (http://javascript%3Cb%3E%3C/b%3E:AL_get%28this,%20%27jour%27,%20%27J%20Physiol.%27%29;) 2006 Oct 1;576(Pt 1):55-62. Epub 2006 Aug 10. Related Articles, (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?itool=pubmed_Abstract&db=pubmed&cmd=Display&dopt=pubmed_pubmed&from_uid=16901948) Links (http://javascript%3Cb%3E%3C/b%3E:PopUpMenu2_Set%28Menu16901948%29;) http://www.ncbi.nlm.nih.gov/entrez/query/egifs/http:--highwire.stanford.edu-icons-externalservices-pubmed-notfree-jphysiol-entrez.gif (http://www.ncbi.nlm.nih.gov/entrez/utils/fref.fcgi?itool=Abstract-def&PrId=3051&uid=16901948&db=pubmed&url=http://www.jphysiol.org/cgi/pmidlookup?view=long&pmid=16901948)
Mechanisms underlying the temporal precision of sound coding at the inner hair cell ribbon synapse.

Moser T (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Search&itool=pubmed_Abstract&term=%22Moser+T%22%5BAuthor%5D), Neef A (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Search&itool=pubmed_Abstract&term=%22Neef+A%22%5BAuthor%5D), Khimich D (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Search&itool=pubmed_Abstract&term=%22Khimich+D%22%5BAuthor%5D).

Department of Otolaryngology, Gottingen University Medical School, Robert-Koch-Strasse 40, 37075 Gottingen, Germany. tmoser@gwdg.de

Our auditory system is capable of perceiving the azimuthal location of a low frequency sound source with a precision of a few degrees. This requires the auditory system to detect time differences in sound arrival between the two ears down to tens of microseconds. The detection of these interaural time differences relies on network computation by auditory brainstem neurons sharpening the temporal precision of the afferent signals. Nevertheless, the system requires the hair cell synapse to encode sound with the highest possible temporal acuity. In mammals, each auditory nerve fibre receives input from only one inner hair cell (IHC) synapse. Hence, this single synapse determines the temporal precision of the fibre. As if this was not enough of a challenge, the auditory system is also capable of maintaining such high temporal fidelity with acoustic signals that vary greatly in their intensity. Recent research has started to uncover the cellular basis of sound coding. Functional and structural descriptions of synaptic vesicle pools and estimates for the number of Ca(2+) channels at the ribbon synapse have been obtained, as have insights into how the receptor potential couples to the release of synaptic vesicles. Here, we review current concepts about the mechanisms that control the timing of transmitter release in inner hair cells of the cochlea.

Publication Types:
Research Support, Non-U.S. Gov't (http://javascript%3Cb%3E%3C/b%3E:AL_get%28this,%20%27ptyp%27,%20%27Research%20Support,%20Non-U.S.%20Gov%5C%27t%27%29;)
Review (http://javascript%3Cb%3E%3C/b%3E:AL_get%28this,%20%27ptyp%27,%20%27Review%27%29;)PMID: 16901948 [PubMed - indexed for MEDLINE]
It seems clear that precision is required for performance and this performance is strictly out the range of precision of a neuron. Adding small branches is a very good way to improve a system.

[bernard]

Another thread on the subject
order or chaos or orderly chaos? (http://www.somasimple.com/forums/showthread.php?t=961)

[bernard]

And this paper shows that the functionning window is "narrow".