Neuroethological analysis of visually oriented behavior in honey bees

Abstract

The honey bee is an excellent navigator and visual learner, but we know little how and why it performs so well. Two regions of the honey bee brain are crucial for learning and memory and in orientation in space – the mushroom bodies (MBs) and the central complex (CX). Both regions process major sensory input of different modalities. The MBs are key regions for associative learning. The CX plays a major role in processing visual input to generate a representation of orientation in relation to the environment, and regulates motor output. My aim is to understand the roles the MBs, the CX and adjacent regions of the protocerebrum play in visual learning, locomotion and orientation in the honey bee. I present how neuropharmacological manipulation in free-moving and restrained bees can be used to investigate behavior. The key method for the studies described in this thesis was microinjection of the local and reversible anesthetic procaine into the investigated brain regions. In the first experimental study, I explored the role of the MBs and the CX in an aversive visual learning assay. I concluded that the MBs and the CX both contributed to the behavioral response to a learned visual stimulus. In the second study, I investigated what roles the MBs and the CX play in modifying locomotion and orientation to a visual stimulus. I found that reducing neural activity in one MB calyx by procaine-injections led to lower walking speed and a lower number of walking bouts compared to controls. Injections with procaine into the CX and the adjacent protocerebrum led to an increase in turning in dark conditions compared to controls. Using a new visual sequence learning assay, I present that honey bees could anticipate an upcoming light in a light sequence of three lights with experience. This behavior was impaired after procaine-injections into the CX and the adjacent protocerebrum. In my final review chapter, I discuss how recent research corroborates the CX as key structure for generation and reading of the waggle dance. Finally, I discuss how my findings contribute to understanding of how visual information is processed and integrated by the insect brain to generate the appropriate motor response.