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Abstract

This dissertation applies a comparative neuroethological framework to investigate how diverse animals process behaviorally relevant sensory information in the central nervous system. Specifically, I focus on three case studies: somatosensation in birds, vision in frogs, and gustation in mosquitoes. In Chapter 2, in vivo extracellular recordings were used to map tactile responses in two avian forebrain regions, the nucleus basorostralis (Bas) and rostral Wulst (rWulst), of Anna’s hummingbirds and zebra finches. Both species exhibited modular, topographic representations, with cranial and post-cranial regions mapped separately in Bas and rWulst. Hummingbirds displayed lower mechanosensory thresholds and smaller receptive fields than finches, and both species showed heightened sensitivity in behaviorally important areas such as the beak and feet. Building on earlier research, these findings add comparative data from two discrete taxa, contributing to a broader understanding of avian somatosensory organization. Chapter 3 examined a deceptive visual signal, the pedal lure, in cannibalistic South American horned frogs. Behavioral experiments showed that the visual lure is triggered specifically by moving conspecifics, and kinematic analysis identified a dual-frequency hindlimb movement pattern mimicking insect prey. Electrophysiological recordings in the optic tectum showed representation of upper frontal visual field occupied much of the tectal surface, and many of these neurons responded to both prey and the lure. Behaviorally, pedal lure elicited rapid, accurate predatory strikes, supporting its role as an aggressive mimicry signal that co-opts an ancestral prey-detection circuit. In Chapter 4, the central projection patterns of gustatory receptor neurons expressing five distinct receptors (GR4, GR14, PPK301, IR25a, IR76b) were examined through 2D visualization and 3D registration in the subesophageal zone (SEZ) and ventral nerve cord (VNC) of Aedes aegypti. The projection patterns generally reflected receptor expression in peripheral taste organs. However, unlike Drosophila, the large overlap of projections in the SEZ among the five genotypes suggests reduced modality segregation in mosquitoes. Sexual dimorphism was also unexpectedly minimal, despite pronounced behavioral differences. These results warrant further research to better understand gustatory coding in insects. Overall, this study shows that a comparative approach can reveal both conserved coding strategies and specializations reflecting the unique sensory demands of each species.