Neuronal mechanisms of merging multi-modal information and modulation through experience

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Multi-modal integration and its neuronal computation are central to sensory perception as the environment always comprises a composition of different sensory modalities. How brains manage to extract the relevant features and combine single modalities to a common percept is yet not fully understood. My goal is to extend our rather limited understanding on the neural mechanisms underlying multi-modal integration and experience dependent sensory perception. Due to its sensory ecology and neurobiology the honeybee represents a favorable model to investigate neuronal principles of multi-modal integration, in particular influences of olfactory-visual integration on single-modality perception. The project is focused on mushroom body output neurons (MBON) as from a neuronal circuit perspective these neurons represent the first level of olfactory-visual convergence in honeybees. I have set up a recording rig allowing for registration of MBON activity over many hours during stimulation with monochromatic light and single odor components. Preliminary data show that ~50% of the recorded MBONs respond to both modalities (odor and light). I hypothesize that these MBONs comprise a neuronal substrate for multi-modal integration and its experience dependent modulation, which will be characterized in the proposed project. As an initial step defined odor and light stimuli will be presented in a unimodal as well as in a multi-modal (compound) fashion and the MBON activity will be analyzed. The results will uncover principals of neural coding after olfactory-visual convergence. Next, I will investigate how the association of an odor-light compound with a reward influences the neuronal representations of the single components (odor and light). To test this, classical conditioning experiments that are well established in honeybees will be performed. Bees will be trained to associate an olfactory-visual compound stimulus with a reward. Subsequently, we will test if the bees respond to the compound only or if the single stimulus components (odor and light) may as well trigger a response. In a final step I will combine classical olfactory-visual conditioning (behavior) with MBON recordings (electrophysiology) and analyze how the common reward association affects the neural representation of the single components compared to the olfactory-visual compound. Using multi-unit long term recordings in combination with classical conditioning experiments in honeybees I could already show that MBONs encode the odor reward association. Moreover, recently I found that in addition to the odor identity the odor reward association includes the information about the antennal stimulation side, adding a spatial dimension. Thus, MBONs integrate different features of the reward associated stimulus situation. With the planned project I expect significant advance in our understanding of the neuronal mechanisms underlying multimodal integration and its experience dependent modulation.