Activation of specific mushroom body output neurons inhibits proboscis extension and feeding behavior

Abstract

The ability to modify behavior based on prior experience is essential to an animals survival. For example, animals may become attracted to a previously neutral odor or reject a previously appetitive food source upon learning. In Drosophila, the mushroom bodies (MBs) are critical for olfactory associative learning and conditioned taste aversion, but how the output of the MBs affects specific behavioral responses is unresolved. In conditioned taste aversion, Drosophila shows a specific behavioral change upon learning: proboscis extension to sugar is reduced after a sugar stimulus is paired with an aversive stimulus. While studies have identified MB output neurons (MBONs) that drive approach or avoidance behavior, whether the same MBONs impact proboscis extension behavior is unknown. Here, we tested the role of MB pathways in modulating proboscis extension and identified 10 MBON split-GAL4 lines that upon activation significantly decreased proboscis extension to sugar. Activating several of these lines also decreased sugar consumption, revealing that these MBONs have a general role in modifying feeding behavior beyond proboscis extension. Although the MBONs that decreased proboscis extension and ingestion are different from those that drive avoidance behavior in another context, the diversity of their arborizations demonstrates that a distributed network influences proboscis extension behavior. These studies provide insight into how the MB flexibly alters the response to taste compounds and modifies feeding decisions.