An advanced surgical microscope for novel studies of sensorimotor integration for flight control

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A key role of the brain is to synthesize sensory information for the control of movement. Most neuroscience research occurs in restricted preparations, which leaves a major gap in our understanding of the control of complex motions required for free movement. Maneuverability is critical for survival, and susceptible to disease, injury, and ageing. My laboratory group uses hummingbirds and zebra finches as research models because their well-defined visual pathways and extremely maneuverable flight can be studied in an experimental setting. We are now using new technologies to study the brain in freely flying birds, something which was not previously possible. However, we lack one essential piece of equipment, a modern surgical microscope. In recent studies, my group investigated how visual signals are processed in the brain and transformed into motor commands for fundamental control tasks including velocity, centering, decelerating, obstacle avoidance, group behaviour (flocking), and holding station (hovering). Through a previous RTI grant, we developed an integrated flight arena that includes automated flight tracking of 3D trajectories, real-time closed-loop visual stimulus presentation, and a moving track that allows electronics to travel with the flying bird for simultaneous electrophysiological recording and optogenetic activation. There is no other laboratory in the world with these capabilities. A significant challenge to our work is that there are no modern surgical microscopes available in our building or department. The two available scopes date from the middle of the last century and have poor optical resolution, lighting, and control. The ability to make chronic implants for employing tetrode recordings and optogenetic stimulation requires a state-of-the-art surgical microscope that has four essential features: 1) high resolution optics over an extended depth of field, 2) directed light sources for optical resolution in deep cavities, 3) hands-free optical control, and 4) stable positioning and flexible 6-axis maneuverability to cope with the movement of wires, cables, and visual monitors around an animal subject. To facilitate the efficient transmission of skill for expertise to HQP, the scope also requires video recording and display, and an assistant's objective. A modern surgical scope will allow for investigation of the neural circuits that control complex locomotion, research that is not otherwise possible. Three specific questions that will guide this work are: a) how do solitary versus social flyers encode the motion of other birds, whether in the object motion visual pathway or in the optic flow visual pathway?; b) how do the major optic flow nuclei contribute to the encoding of distinct guidance algorithms for forward motion?; c) are distinct guidance algorithms between hovering and forward flight mediated by efference copy suppression of optic flow signals?