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I found the following pictures of axon trees:

enter image description here

source

enter image description here

source (axons are red)

but didn't find a concise answer to the following question:

How many (in relative terms) branches terminate and how many axon terminals (synapses) are there in the different target regions of a typical cortical pyramidal cell, i.e.

  • same cortical layer

  • other cortical layers

  • same cortical column

  • other cortical columns

  • more distant cortical regions (e.g. in the same gyrus)

  • subcortical regions

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  • $\begingroup$ I take it that you mean how many synapses are formed with a pyramidal neuron and $X$. Talking about branches doesn't make too much sense. You should know that there are 4-7 different types of cortical pyramidal cells, depending on how you count (e.g. Oberlaender et al. 2012 for the higher estimate). Every single presynaptic source you are asking about is going to have a different estimate for every different type of pyramidal neuron, and some of them are unknown. I'd say this is too broad. $\endgroup$ – vkehayas Oct 17 '17 at 18:43
  • $\begingroup$ You "just" say there is no typical pyramidal neuron? I know that $\endgroup$ – Hans-Peter Stricker Oct 17 '17 at 19:15
  • $\begingroup$ ... but 4-7 is not such a big number one couldn't give a partial answer: for type X it is so-and-so, ... Should I rephrase my question? To which of the 4-7 types would you recommend to restrict my question? $\endgroup$ – Hans-Peter Stricker Oct 17 '17 at 19:20
  • $\begingroup$ I'd say we only have numbers for the number of synapses or the volume of axon that comes or goes inside or outside the column, with no estimates about specific neurons, but I really do hope that someone will prove me wrong. $\endgroup$ – vkehayas Oct 17 '17 at 20:23

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