Speaker
Description
The European honeybee, Apis mellifera, is a favourable experimental model for investigating cross-modal sensory interactions, particularly olfactory-visual integration, at both the behavioural and neuronal levels. Such integration occurs in high-order processing centres called mushroom bodies (MB), which receive sensory information from primary olfactory and visual centres, the antennal and optic lobes (AL and OL, respectively). Axon terminals of projection neurons from the AL and OL form synaptic complexes with MB intrinsic neurons, the Kenyon cells, in the MB calyx. The information is then transferred via Kenyon cell axons to the MB output regions, the medial and vertical lobes. Here, Kenyon cell axons converge synaptically with MB output neurons (MBONs), which form short-range recurrent connections to the MB calyx and centrifugal long-range connections to the AL, lateral horn, and other regions of the protocerebrum. It has been shown that individual MBONs respond to odour or light stimuli, and a substantial proportion is sensitive to both odour and light stimuli (Strube-Bloss & Rössler 2018, Roy Soc Open Sci). This shows that multimodal convergence is present at the MB output level. Are differential responses to the two sensory modalities represented in morphologically distinct MBON clusters? How is cross-modal information distributed to upstream and downstream olfactory processing centres? We perform electrophysiological intracellular recordings from MBONs in the MB vertical lobe while presenting adult honeybees with an olfactory-visual stimulation protocol to physiologically characterize individual MBONs. We combine this with iontophoretic current injections and fluorescent labelling techniques to identify the anatomical convergences of individual MBONs with the AL, lateral horn and other parts of the protocerebrum. We use a recently established detailed 3D atlas of the honeybee brain (Habenstein et al. 2023, J Comp Neurol) as a reference for mapping target innervation patterns of MBONs in upstream and downstream olfactory neuropils. We show cases of MBONs responding to light stimuli that provide centrifugal input to olfactory centres, such as the AL, indicating long-range feedback modulation of olfaction via visual input. Ultimately, our studies aim to better understand cross-modal interactions underlying context- and experience-related modulation of olfactory processing and olfactory-visual perception.
Supported by DFG (FOR grant #466488864 to WR)
