The role of intensity, temporal synchrony, and biogenic amines for unimodal and multimodal integration during learning and memory of honey bees and bumble bees
Thesis
Multisensory integration is a fundamental aspect of learning and memory across animals and is particularly relevant during ecological tasks such as foraging and pollination. This study aimed to investigate the influence of external physical properties of unimodal elements of a composed signal such as intensity and the temporal relationships (synchronicity and order) on the multimodal integration of olfactory and visual signals in honey bees. Furthermore, this study targeted the exploration of the impact of biogenic amines on unimodal and multimodal learning and memory processes in bumble bees, recognizing the crucial role of the inner neuromodulatory environment in the formation of rewarding associations. Through an electromechanical setup, bees were trained using precisely controlled intensity levels and temporal relationships (sync /out of sync /alternate orders presentation) of unimodal and bimodal stimuli. The Proboscis Extension Response (PER) conditioning protocol was employed as a measure of reward learning. To manipulate the neuromodulatory environment of bumble bees, oral administration of biogenic amines, octopamine (OA) and dopamine (DA) agonist 6,7-ADTN was employed. Our findings support the Principle of Inverse Effectiveness (PoIE), indicating that bimodal stimuli are more effectively learned and retained when the individual unisensory responses are relatively weak. The interaction between synchrony and intensity significantly influenced bimodal learning and memory, with maximal enhancement observed at low intensities and synchronous stimuli. Furthermore, our investigation into the role of biogenic amines revealed concentration-dependent and opposing effects OA and DA during unimodal and bimodal appetitive learning. Higher doses of OA improved performance across all modalities, while DA had modality and dose-dependent inhibitory effects. These results provide valuable insights into the complex mechanisms and neural modulation underlying appetitive learning tasks in bees, contributing to our understanding of their behavioural adaptation to complex signals. Ultimately, these findings suggest remarkable parallels between the mechanisms of multisensory integration and rewarding systems in bees and vertebrates. These shared characteristics underscore the significance of bees as a valuable comparative model in neuroscience research.
