Figure 1

(a) Two human (left) and mouse (right) pyramidal cells’. Basal arbor is shown in red; main apical dendrite in black; apical collateral dendrites in blue, and axons in green (adapted from Ref.²⁰). (b) Branch frequencies per species, branch type, and branching order. (c) An illustration of the computed morphometrics and morphological determinants. A branch (or dendritic segment) is defined as a sequence of cylinders between consecutive bifurcation points or between a bifurcation point and a terminal point (each branch shown with a different color). Branch orders (variable branch_order) are computed centrifugally, with branch order 1 corresponding to branches emanating from the soma (the black branch). The length (length) of a branch is the sum of the lengths of its cylinders. The average diameter (diameter) of a branch is the weighted average of the diameters of the branches’ cylinders. There are two types of branches (variable branch_type): non-terminal branches (black, red and orange branches) and terminal. The distance from the soma (distance) is the length of the straight line from the dendrites’ insertion point into the soma up to the starting point of a branch (e.g., for the green branches, this is the distance between S and G). Variables distance, length, and diameter are all measured in micrometers (µm). tortuosity describes dendritic meandering and is defined as the ratio of length and the length of the straight line between the beginning and the end of a branch; it is a unitless quantity and tortuosity \(= 1\) denotes a perfectly straight branch whereas increasing values denote more tortuous branches. Remote bifurcation angle (bifurcation_angle) is the shortest planar angle between the vectors from the bifurcation to the endings of the daughter branches; for the red branch, it is the smaller angle between points GA, G, and GB. Remote tilt angle (tilt_angle) is the smallest angle between the branch director vector and the vectors from the bifurcation to the endings of the daughter branches. bifurcation_angle and tilt_angle are measured in radians. bifurcation_angle and length are undefined for terminal branches, as they do not bifurcate. The taper rate is ratio of the difference between the diameter of the first and last point of a branch and the diameter of the first point.