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Neural basis of a visuo-motor transformation in the fly 10.17863/CAM.16391 Huston, Stephen How the outputs of populations of sensory neurons are used by motor systems to generate appropriate behaviour is a long standing question in neuroscience. I address this problem by studying a comparatively simple model system. In the fly, Neck Motor Neurons control gaze-stabilising head movements that occur during wholebody rotations. These motor neurons receive several sensory inputs including one from well-characterized visual interneurons, Tangential Cells (TCs), which respond to panoramic image shifts induced during self-motion. In chapter one, I provide a general introduction to sensory-motor circuits and the fly gaze-stabilisation system. In chapter two, I report that the visual receptive fields of Neck Motor Neurons are similar to those of the TCs. Using this result, I show an alignment between the coordinate systems used by the visual and the neck motor systems to process visual information. Thus, TCs encode visual inputs in a manner already closely matched to the requirements of the neck motor neurons, considerably facilitating the visual-motor transformation In chapter three, I analyse the gating of neck motor neuron visual responses by convergent mechanosensory inputs from the halteres. Some neck motor neurons do not fire action potentials in response to visual stimuli alone, but they will in response to haltere movements. I show that visual stimuli produce sustained sub-threshold depolarisations in these neurons. These visual depolarisations increase the proportion of haltere-induced action potentials in neck motor neurons. Thus, visual inputs can only affect the spiking output if the halteres are moving. This simple mechanism could explain why flies only make visually induced head movements during walking or flight: behaviours that involve beating the halteres. By analysing how the outputs of a model sensory system are used, I have shown a novel alignment between sensory and motor neuron populations and a simple mechanism underlying multisensory fusion. University of Cambridge 2006-01-17 Thesis Doctoral Doctor of Philosophy (PhD) en http://www.dspace.cam.ac.uk/handle/1810/220933 https://www.repository.cam.ac.uk/handle/1810/220933 https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/97b41f08-8143-4ca8-b965-5f59baac8de5/download a5dfc4af5e32f535ec13bd9d1e39c25f https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/a0dd6791-e244-4995-907f-d9d414ef523a/download a170f3155a98365e9971bff694720be3 https://www.rioxx.net/licenses/all-rights-reserved/ 2009