A question on the computation of laminar termination patterns in the cortex (Harris et al., 2019)

Dear all,

I am reading the article “The hierarchical organization of thalamic and cortical connectivity” by Harris et al., 2019.

I would like to know in detail which formula is used to compute what is referred to as a “laminar termination pattern” of a projection. On page 209 of the method section, the paragraph entitled “Clustering analyses” gives this definition:

“Relative layer density is the fraction of the total projection signal in each layer, scaled by
the relative layer volumes in that target.”

I am unsure of what “scaled” means and I don’t really know by what one is supposed to multiply or divide the connection strength.

Assume that we are given a source and a target region. Is there a simple formula to describe a “relative layer density” using the terminology of “High-resolution data-driven model
of the mouse connectome” by Knox et al., 2018?

In the latter article definitions such as “connection strength” are expanded in the margin, leaving no chance to wrong interpretation.

Many thanks in advance for your answer!


I got a reply via email from Hannah Choi. This fully answers my question:

The “relative projection density per layer” is computed as [projection volume in the target layer / projection volume per target]/ [volume of target layer / volume per target]. Here, projection volume is the volume of projection signal in structure in mm^3. Therefore, the quantification “relative projection density per layer” is unitless.

Thanks again Hannah!