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Basic Neuron Questions

Didier A. Depireux didier at rai.isr.umd.edu
Mon Apr 7 16:27:23 EST 2003

Neo <neo55592 at hotmail.com> wrote:

> Also, in the cerebral cortex, how common is it for a neuron in a chain
> to loop back to the 2nd neuron prior to itself? Suppose N1 -> N2 -> N3
> -> N4. Does N3 commonly connect back to N1, does N4 commonly connect
> back to N2, etc.

I doubt anyone knows the answer to that question in any detail. For any
projection, you have a back-projection. For instance, for primary sensory
areas, the number of fibers projecting from cortex back to thalamus is about
10 times the number of projections from thalamus to cortex (but the
projections back to thalamus are thin fibers). 
We are pretty sure you have a closed look if you include reticulum in your
loops, but that's not part of neocortex.

Look at the article
"On the Dimensionality of Cortical Graphs "
it's an interesting read that addresses your question in a statistical


Didier A Depireux         ddepi001 at umaryland.edu  didier at isr.umd.edu
685 W.Baltimore Str      http://neurobiology.umaryland.edu/depireux.htm
Anatomy and Neurobiology                      Phone: 410-706-1272 (off)
University of Maryland                                      -1273 (lab)
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