Elucidating the Role of ON and OFF Visual Pathways in Object Segmentation for Escape Behavior

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The project will investigate how the nervous system generates specific responses to visual stimuli associated with objects approaching on a collision course. Reliable and precise responses to such stimuli is often critical to take evasive actions and may be the difference between life and death in many situations. The project will use the nervous system of grasshoppers and locusts for these investigations as the neural processing underlying collision avoidance is particularly well understood in these animals. The project will gather data using a variety of experimental techniques and model the neural pathways responsible for the visual detection of approaching objects leading to collision avoidance under different simulated environmental conditions. A better understanding of the biological mechanisms leading to the robust detection of approaching objects may help design more robust and energy-efficient artificial collision avoidance systems such as small drones or portable devices for blind people.Despite decades of work, the large-scale visual processing that results in visual object segmentation or identification remains poorly understood. In grasshoppers, the postulated mechanisms of object segmentation for collision avoidance and escape behavior rely on complex processing within the extended dendritic tree of a single neuron resembling in its morphology and synaptic organization that of a Purkinje cell in the cerebellum. Synaptic inputs impinging on this neuron are segregated into ON and OFF pathways with distinct anatomical properties allowing to investigate how they combine to encode textured stimuli mixing both contrast polarities. Several conductances involved in the processing of OFF inputs are ubiquitous in the dendrites of a wide range of neuron types. Thus, understanding how these conductances implement object segmentation will shed light on how they could implement similar neural computations across the nervous system. These dendritic conductances interact with Ca+2 and Ca+2-activated K+ conductances located close to the spike initiation zone that switch the neuron's firing mode between tonic and bursting. This project will shed light on how transitions between these two firing modes contribute to neural computation, as has been postulated in other sensory systems. The results are expected to shed light on how complex sensory information contributes to the generation of escape behaviors by integrating results at different levels of complexity, ranging from single conductances to whole organisms.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.