Biophysical constraints on neuronal branching

We investigate rules that govern neuronal arborization, speci%cally the local geometry of the bifurcation of a neurite into its sub-branches. In the present study we set out to determine the relationship between branch diameter and angle. Existing theories are based on minimizing a neuronal volume cost function, or, alternatively, on the equilibrium of mechanical tension forces, which depend on branch diameters. Our experimental results utilizing two-dimensional cultured neural networks partly corroborate both the volume optimization principles and the tension theory. Deviation from pure tension forces equilibrium is explained by an additional force exerted by the anchoring of the junction to the substrate. c © 2004 Elsevier B.V. All rights reserved.