"The insect compass system: From theory to circuitry" by Vilimelis et al. 2023 https://www.biorxiv.org/content/10.1101/2023.07.05.547838v2
Interesting insight on extra-genomic contributions to neural circuit architecture:
"we demonstrate that our predicted circuit can emerge naturally using Hebbian plasticity, which means the neural connectivity does not need to be explicitly encoded in the genetic program of the insect but rather can emerge during development."
And particularly:
"we now address another question: whether there might be a reason that insect head direction circuits typically have an eight-column architecture [...] powers of two are easier to generate with replication dynamics than other numbers, because they just require each cell to divide a set number of times."
"The circuits for N = 2 and N = 4 are degenerate – either producing a single dimensional encoding, or two disconnected circuits that do not enforce the required circular topology. N = 8 is the smallest power of two that could result in a non-degenerate circuit. This hints at the possibility that the eight-column architecture is not a chance evolutionary artefact, but rather that it is the genetically simplest circuit capable of performing heading integration."