Gaze control is a fundamental task that is solved by most visually oriented animals including humans. The neural pathways involved receive input from several sensory systems each of which is tuned to a certain fraction of the overall dynamic stimulus range. How is local information obtained in modality-specific coordinates integrated and transformed into signals that are compatible to the motor coordinate system controlling the gaze? This question addresses several major topics in neuroscience including task-specific sensory feature extraction, multimodal integration, sensorimotor transformation and – in some cases – the use of forward models to refine sensory processing and motor performance.
The fly is a well-established model system for studying the functional organization of sensorimotor control. Its compound eye-driven visuo-motor system has been successfully analysed using anatomical, physiological and neurogenetic approaches in combination with modelling studies in the context of gaze and flight control. Mostly, however, the impact of individual modalities on these behaviours were studied in isolation, and for a given motor state. My presentation will focus on the response properties of an identified population of motion sensitive interneurons in the blowfly, the lobula plate tangential cells (LPTCs). These cells analyse panoramic optic flow patterns and provide the animals with relative distance and self-motion information. Our recent studies suggest (i) that LPTCs play a major role in the transformation of sensory to motor coordinates along the gaze control pathway, (ii) that the activity of a subset of LPTCs, the vertical system cells, does not only depend on compound eye-mediated motion stimuli but is also strongly modulated by input from the fly’s second visual system, the ocelli, and (iii) that an octopamine agonist, which is thought to induce a ‘fictive flight’ state, increases the performance of spiking LPTCs in analysing self-motion parameters.
We are currently developing a new experimental paradigm to study multisensory integration in locomotor-active animals and to assess the possible use of efference copies in visuo-motor pathways under closed-loop conditions.
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