UCLA

As we move through the world, our visual system constantly detects and tracks objects around us, using cues such as movement, texture, brightness, color and shape. A solid mechanistic understanding of how an object is distinguished from its background has eluded researches examining this question across many model organisms. In this thesis, we describe a novel object-detecting neuron class in the fly optic lobe by characterizing its anatomy and physiology. We then show direct evidence that inhibitory currents play a major role in mediating object-selectivity. To find origins of inhibition, we screen publicly available libraries and identify candidate presynaptic input neurons. In addition, we examine the receptor expression profile of object-detecting neurons and identify receptor types that are likely to mediate inhibition and excitation. Our results provide insights into the only known object-detector neuron in Drosophila.

To elucidate the possible behavioral contributions of object-detecting neurons, we investigate the object tracking behavior in flies. We show that luminance and motion cues contribute to object tracking behavior in distinct ways. Specifically, flies exhibit quantitatively and qualitatively distinct behavioral responses to luminance-defined and motion-defined objects. Our results complement previously published research and demonstrate the existence of parallel visual streams carrying different information (motion or luminance) that are relevant for object tracking behaviors.