Flexible Visuomotor Transformation in Larval Zebrafish

Abstract

Sensorimotor transformations enable animals to respond adaptively to environmental stimuli by integrating sensory input, internal states, and contextual cues into motor outputs. However, the neural circuits underlying these flexible transformations remain incompletely understood. Using larval zebrafish as a model, this thesis systematically explores the neural basis of visually induced innate behaviors—hunting, freezing, and escape—employing brain-wide two-photon calcium imaging combined with precise behavioral analysis. We established that a slow-moving, dark sweeping disk robustly induces freezing behavior, characterized by both immobility and bradycardia. Through comparative analyses, we showed significant overlap among sensory neuron populations responding to prey-like stimuli, sweeping threats, and looming stimuli in the optic tectum. Conversely, sensorimotor populations were highly selective, distinctively segregated for each behavior within tectal layers. This functional divergence suggests a hierarchical organization whereby sensory information is broadly represented and progressively refined into specific motor commands. These findings position the optic tectum as a central hub orchestrating sensorimotor integration and behavior selection through context-dependent mechanisms. This thesis elucidates fundamental principles governing sensorimotor transformations, advancing our understanding of neural circuit flexibility and decision-making in vertebrates.

Date of Award	2025
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology
Supervisor	Julia Lee SEMMELHACK (Supervisor)