The neural circuitry of learning, memory, and decision-making in honey bees

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The western honey bee (Apis mellifera) is renowned for its complex behaviour. It can learn the times of day of food availability and the locations of availability for multiple simultaneous food sources. It can memorize and count landmarks and follow UV light patterns in the sky (the "sun compass") to navigate to known food sources. It can then return home and communicate the locations of food sources to its hivemates via a symbolic language called the "waggle dance", wherein the direction and distance of the source are communicated by body movements. Humans have exploited bees for honey and wax for 9000 years and actively kept domesticated bees for half that time. However, while even Aristotle was known to keep bees, careful bee experimentation did not begin until the 18th century. Even now, we are only beginning to understand the neural underpinnings of behaviour in any animal. Neuroethology is the study of brain structure and function from an evolutionary and comparative perspective. It focuses largely on how brains produce behaviour. Because the honey bee has an unusually large brain for an insect, measuring about 1 mm3 and containing nearly 1 million neurons, and because the honey bee possesses such an impressive repertoire of complex behaviours, the honey bee is an ideal research animal in neuroethology. Discovering how honey bee brains produce behaviour is the long-term objective of my research program. In this grant cycle, my lab will continue to explore the organization of an important insect brain region called the mushroom bodies (MB), which are involved in sensory integration, learning, and memory. We will train bees to perform complicated sensory learning tasks and look at how this information is coded in the brain. We will also look at how the brain changes due to these experiences. There is limited evidence that learning occurs both in the MB input regions (the calyces) and the MB output regions (the lobes). We will ultimately learn how this information is combined and compared with other information streams in the brain to understand how decisions are made. This work is important for two reasons. First, while insect brains are different than human brains, to a large extent a neuron is a neuron. Understanding structure and function in a more tractable brain will guide us as we try to understand brain structure and function (and loss of function) in humans. Second, pollinator health is of serious concern worldwide right now. With loss of habitat, increased pesticide use, and new invasive pests, pollinator numbers have been declining for decades. Honey bee pollination alone is a $2.5 billion industry in Canada and a $200 billion industry worldwide. Considering pollinators are responsible for about a third of our food, solving problems in sensory integration, learning, and decision making in insects is critical and may lead to novel tools in ecosystem service, increasing pollinator efficiency, and possibly increasing crop yield.