Stochastical organisation of cortex?

Lester Ingber ingber at umiacs.umd.edu
Sun Jun 28 19:48:26 EST 1992


Not only is there evidence for "statistical" connectivity, e.g., with
respect to a regional scale, but also there is evidence for dynamic
stochastic activity, e.g., as induced from statistics of synaptic
activity, which carries up to columnar and regional scales.  Some
references are:
%A L. Ingber
%T Statistical mechanics of neocortical interactions:
A scaling paradigm applied to electroencephalography
%J Phys. Rev. A
%S 6
%V 44
%P 4017-4060
%D 1991
 
%A J.W. Clark
%A J. Rafelski
%A J.V. Winston
%T Brain without mind: Computer simulation of neural networks
with modifiable neuronal interactions
%J Phys. Rep.
%V 123
%P 215-273
%D 1985
 
%A K. Obermayer
%A G.G. Blasdel
%A K. Schulten
%T Statistical-mechanical analysis of self-organization
and pattern formation during the development of visual maps
%J Phys. Rev. A
%V 45
%S 10
%D 1992
%P 7568-7589


}From: ddoherty at ics.uci.edu (Donald Doherty)
}Newsgroups: bionet.neuroscience
}Subject: Re: Stochastical organisation of cortex?
}Date: 28 Jun 92 22:59:16 GMT
}References: <1992Jun28.201116.23454 at rhrk.uni-kl.de>
}Reply-To: ddoherty at ics.uci.edu (Donald Doherty)
}Organization: Univ. of Calif., Irvine, Info. & Computer Sci. Dept.
}
}In article <1992Jun28.201116.23454 at rhrk.uni-kl.de> andrick at sun.rhrk.uni-kl.de (Ulf Andrick [Biologie]) writes:
}>There was an article in Spektrum der Wissenschaften (German version of 
}>Scientific American) in May 1989 by Braitenberg and Schuez in which 
}>the authors suggested that the connections between the pyramid cells in the 
}>cerebral cortex are stochastically distributed, so that there is no special 
}>preformed structure. I'm curious to know if this view is commonly shared by 
}>brain physiologists or if it is already out-dated because of newer findings.
}
}
}The best summary of the data available to date that addresses the above
}question (and cortical circuitry in general) has been written by 
}Edward White (1989) "Cortical Circuits."  Ed White is one of a few people
}carrying out experiments that directly address questions of specificity
}of connections at the microcircuitry level.
}
}The short answer to your question is yes and no.  That is, stochastic
}is not equivalent to random.  Within a particular layer (connectivity to,
}from, and between different layers in the cortex is very specific) there
}seems to be a stochastic distribution of connections.  Stochastic
}signifies a randomly determined series of observations, each of which
}is a single element that belongs to a population that obeys a deterministic
}distribution.  Therefore there does seem to be structure and specificity
}to the microcircuitry.
}
}Usually, when connections in the brain are labeled random you can
}replace the word 'random' with 'unknown.'  When actual data are gathered
}the connections that were thought to be random are typically found to be highly
}specific.  Experiments on the microcircuitry of the brain are extremely
}difficult and the number of cells/connections studied are very few.  (We
}are talking about the reconstruction of only a *few* neurons out of
}how many in the brain?)  Nevertheless, it is interesting that there is
}specificity even at the microcircuitry level, although apparently
}stochastic.
}
}Don
}
}P.S.  This is necessarily just a reflection of my personal musing on the
}      subject.  Ed White's book cited above is highly recommended if
}      you want the data and opinions of a master on the subject.  Also,
}      the book may easily be read by non-neuroscience professionals.
}
}-------------------------------------------------------------------------------
}Donald Doherty
}Dept. of Psychobiology		Email:	    ddoherty at ics.uci.edu
}University of California	CompuServe: 76646,1321
}Irvine, CA  92717-4550		FAX:	    (714) 725-2447
}U.S.A.				Voice:	    (714) 856-1776

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