astlab3 at uci.edu astlab3 at uci.edu
Tue Nov 17 14:34:30 EST 1992

In article <2B080857.3179 at news.service.uci.edu> mundkur at falcon.eng.uci.edu (Prashanth Mundkur) writes:

>       Some questions for which I am looking for answers are
>1) How do you conduct an experiment that traces the path of an axon for over
>50 cms? 
>2) How do you say that a neuron responds to a certain stimulus? What exactly is
>involved when one places electrical electrodes on a cell membrane?
>3) Drawing conclusions about a neuron's functional behaviour from brain lesion
>experiments surely is very error-prone. What are the mistakes one should not
>make when drawing conclusions from such experiments?
>4) When one sets up a "mathematical" model of the operation of a set of neurons
>in a particular part of the nervous system, what does one normally take into 
>account, and what does one assume to be irrelevant to the modeling objective?
[comments deleted]
>Thanks for any advice and/or pointers to literature.

	These are some very broad questions, but I will attempt to get you
headed in the right direction.
1)  There are many techniques for tracing the length of an axon.  One of
	first used is to inject horseradish peroixdase into the synapse
	where the axon terminates.  This substance is then taken up into
	the cell and through retorgrade transport marks the whole cell.
	For more info, look into "Neurobiology" by G. Shepard.
2)  Again there are many techniques (ie. voltage clamp, patch clamp, etc.)
	In voltage clamp, the cell is impaled by 2 electrodes, and by
	supplying current, the cell's voltage is 'clamped'.  The current
	supplied to keep the cell at the chosen voltage is equal to 
	the current passing through the membrane by ionic flux.
	Good references are: "Ionic channels of excitable membranes" by
	Hille, and "Physiology of excitable cells" by Aidley.
3)  You are correct in saying that the interpretation of lesion studies
	is often subject to much scrutiny.  This technique is extensively
	used, and there are many methods for producing both reversible
	and non-reversible lesions.  Try "Principles of Neural Science"
	by Kandel, Schwartz, and Jessel.  
4)  Currently the connectionist paradigm is the most popular for modelling
	the functioning of the brain.  The connectionist's bible is 
	"Parallel distributed processing" by some guys at San Diego that
	 I can't recall right now.

	I hope that this will give you a good start.  To answer most
of your questions in detail will require a great deal of reading.  Your
best bet is to begin with "Principles of Neural Science", and look for
more details elsewhere if necessary.  Good luck.

Brooke Paul                                         * bpaul at darwin.
UCI- Department of Psychobiology                    *          bio.
Laboratory of Cellular and Molecular Neurobiology   *          uci.
Irvine, Ca.  92715                                  *          edu
of your	questions    

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