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How does the border between two Brodmann areas look like in Nissl stains? How large is the transition zone where one cannot tell to which of the two areas a neuron belongs to? How many neurons are ambiguous compared to the number of unambiguous ones, roughly? 1%, 5%, 10%?

Is the inner connectivity of a Brodmann area greater than its connectivity with a neighbouring area across the border? Can this be seen in Nissl stains? Or is short-range inner-cortical connectivity somehow homogenuous over adjacent Brodmann areas?

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  • $\begingroup$ Hi Hans, this might be the sort of question that's best answered yourself by looking at some labeled Nissl sections, or by reading about criteria used to determine areas. $\endgroup$ – Bryan Krause Feb 7 at 0:11
  • $\begingroup$ @BryanKrause: I'll try, but I'm afraid my view is too unexperienced. Could you give me a reference explaining the criteria to determine areas? $\endgroup$ – Hans-Peter Stricker Feb 7 at 0:26
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    $\begingroup$ I tried searching Google Images for "brodmann nissl" (but no quotes); one example led me to webvision.med.utah.edu/book/part-ix-brain-visual-areas/… (figure 9 on that page). Figure 1 here: nibb.ac.jp/brish/Gallery/cortexE.html also looks like a place to get started in looking at the layers. Note that there is a huge variety in the discriminability of Brodmann areas (and one reason there are so many different parcellations of cortex): some are really easy, others require an anatomist's trained eye and I can't tell them apart myself. $\endgroup$ – Bryan Krause Feb 7 at 0:47
  • $\begingroup$ I think you'll get a better picture by going through some examples to get a sense for yourself, rather than trying to quantify it. $\endgroup$ – Bryan Krause Feb 7 at 0:47
  • $\begingroup$ @BryanKrause: Figure 9 is great and gives me a better sense: It's about "distinctness of appearance" (in this case of layer 4 which is also present in V2 but not so distinct as in V1). What can be seen also: The border is only sharp in layer 4 (and here, it is astonishingly sharp) but its sharpness does not extend to the other layers: there it becomes diffuse. $\endgroup$ – Hans-Peter Stricker Feb 7 at 8:17

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