In the Wikipedia article on dendritic spikes I read:

In the hippocampus, the CA1 neurons contain two distinctive regions that receive excitatory synaptic inputs: the perforant path (PP) through the apical dendritic tuft (500-750 μm from soma) and the Schaffer-collateral (SC) through the basal and apical dendrites (250-500 μm from soma).

I wonder how the distinctiveness of these two regions does appear when plotting the number of synapses as a function of the distance to the soma:

enter image description here

More like the gray, or more like the red, or more like the green curve? Or which other?


1 Answer 1


One source for this estimate is Megias et al. 2001, an electron microscopy study in CA1 of the rat hippocampus.

I plot their data from Table 3 in the following graph. Total synapse number per dendritic subclass, based on Megias et al. 2001

The X-axis is not in micrometers. Rather it represents dendritic subclasses. $Ori$ stands for Stratum Oriens, $Rad$ for S. Radiatum, $L-M$ for Lacunosum-Moleculare, $T$ for thick dendrites, $t$ for thin dendrites, $prox/med/dist$ for proximal, medial, and distal, respectively. Stratum Oriens represents basal dendrites that are close to the cell body, stratum Radiatum apical trunks, and stratum Lacunosum-Moleculare the apical tufts. The approximate locations of the layers in reference to the cell body are (in micrometers): $Ori = (-100, 0)$, $Rad = (100, 350)$, $L-M = (350,550)$. The Y-axis represents the total number of synapses, both excitatory and inhibitory.

  • $\begingroup$ Isn't it possible to attach rough distances to the dendritic subclasses? Since distance to the soma is important. $\endgroup$ Commented Oct 4, 2017 at 12:44
  • $\begingroup$ What does a negative distance mean? $\endgroup$ Commented Oct 4, 2017 at 13:39
  • $\begingroup$ If we assign the cell body, or more precisely the stratum pyramidale, at $0$, then stratum oriens is to its dorsal side and stratum radiatum on its ventral side. I've arbitrarily assigned dorsal $\rightarrow$ ventral as the positive direction. $\endgroup$
    – vkehayas
    Commented Oct 4, 2017 at 13:52
  • $\begingroup$ But the effective (physical) distance is still positive, isn't it? $\endgroup$ Commented Oct 4, 2017 at 13:56
  • $\begingroup$ How could the soma distinguish between dorsal and ventral? $\endgroup$ Commented Oct 4, 2017 at 13:57

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