Olfactory perception and learning in the honey bee (Apis mellifera): calcium imaging in the antenna lobe

Honey bees are a key-model in the study of learning and memory, because they show considerable learning abilities, their brain is well described and is accessible to a wide range of physiological recordings and treatments. We use in vivo calcium imaging to study olfactory perception in the bee brain, and combine this method to appetitive olfactory conditioning to unravel the neural substrates of olfactory learning. Odours are detected by receptor neurons on the antennae. Each receptor neuron projects to the first-order neuropile of the olfactory pathway, the antennal lobe, connecting to projection neurons in one of its 160 functional units, the glomeruli. In calcium imaging experiments, each odour elicits a particular activity pattern of antennal lobe glomeruli, according to a code conserved between individuals. The antennal lobe is also a site where the olfactory memory is formed. Using optical imaging, two studies have shown modulations of odour representation in the antennal lobe after learning, with different effects depending on the type of conditioning used. While simple differential conditioning (A + B- training) showed an increased calcium response to the reinforced odour, side-specific conditioning (A + B-/B + A- training) decorrelated the calcium responses of odours between brain sides. This difference may owe to the formation of different memories, which will be addressed in future work. By specifically staining antennal lobe neuronal subpopulations, we hope to be able in the future to study synaptic plasticity in the honey bee.