A framework for constructing insect steering circuits

Insects perform a variety of goal-directed navigation behaviours, in which steering is controlled by a comparison between their current and desired heading direction. Recent work has uncovered the details of such a steering circuit in the fruit fly Drosophila melanogaster. Here we analyse the principles behind the neuroanatomy and physiology of this circuit to derive five general rules which can be used to construct a class of steering circuits which operate in the same way. These rules are surprisingly permissive, suggesting that across insect species, steering circuits may have differing wiring while remaining functionally identical. We simulate several examples, including an irregular circuit that conforms to the rules, and circuits that break the rules, and examine their ability to control steering towards a varying goal direction. We argue that the principled approach we apply here could be applied more generally in performing comparative analyses in neuroscience.