Mosaic evolution of a learning and memory circuit in Heliconiini butterflies
A critical function of central neural circuits is to integrate sensory and internal information to cause a behavioural output. Evolution modifies such circuits to generate adaptive change in sensory detection and behaviour, but it remains unclear how selection does so in the context of existing functional and developmental constraints. Here, we explore this question by analysing the evolutionary dynamics of insect mushroom body circuits. Mushroom bodies are constructed from a conserved wiring logic, mainly consisting of Kenyon cells, dopaminergic neurons and mushroom body output neurons. Kenyon cells carry sensory identity signals, which are modified in strength by dopaminergic neurons and carried forward into other brain areas by mushroom body output neurons. Despite the conserved makeup of this circuit, there is huge diversity in mushroom body size and shape across insects. However, an empirical framework of how evolution modifies the function and architecture of this circuit is larg