Innate and Learned Valence in Honey Bee Odour Mixture Processing

Apis mellifera encounter odours as mixtures and must integrate components with different biological relevance. This project investigates how pheromones and learning modify the representation of binary odour mixtures in the antennal lobe and their behavioural expression. Preliminary behavioural results show that, 24 hours after appetitive conditioning, bees respond positively to the learned odour presented alone and when mixed with a neutral odour. However, presenting the learned odour together with a negatively valenced pheromonal component interferes with the expression of appetitive memory. To investigate the underlying neural mechanisms, we performed calcium imaging of antennal-lobe projection neurons during stimulation with aversive pheromones and unlearned odours, presented both alone and in mixtures. The results indicate that, in mixtures with neutral odours, pheromonal components contribute more strongly to the neural representation of the mixture. This suggests that pheromones may dominate or modify the early sensory coding of otherwise neutral environmental odours. Calcium-imaging experiments using learned odours are currently underway. These experiments will determine whether learning modifies this weighting and shifts the representation of the mixture towards the odour associated with reward. Overall, these findings contribute to our understanding of how combinatorial coding, innate valence and experience interact during odour-mixture processing in the honey bee.