The Visuomotor Transformation of Target-directed Behaviors in Larval Zebrafish

Abstract

Reacting appropriately to visual stimuli is essential for survival across species. Animals detect prey or predators with their visual system and respond with hunting or defensive behaviors, respectively. However, how visual information is integrated and transformed into motor output is not well understood. In this study, we first established a novel behavioral assay to induce freezing in larval zebrafish using a dark sweep virtual disk, suggesting that visually evoked freezing behavior is evolutionarily conserved. To study the relationship between the circuits for hunting, freezing, and escape, we imaged the larval brain at single-neuron resolution while simultaneously inducing the three behaviors with the corresponding visual stimuli. For each stimulus-behavior pair, we systematically identified sensory neurons that periodically responded to the sensory stimulus. Additionally, we characterized the sensorimotor population that is robustly responsive during behavioral trials. We found that the optic tectum contains broadly tuned sensory neurons and sensorimotor neurons that respond specifically during one behavior. Causal inference analysis supports a direct connection between these two functionally and anatomically distinct tectal populations, suggesting that the tectum is a site of sensorimotor transformation. Furthermore, the segregation of these pathways continues in downstream brain areas, showing that sensorimotor pathways have already diverged at the level of the tectum. Our results support a model in which the tectum integrates object identity and internal state to flexibly transform visual information into different behavioral outputs, providing a deeper understanding of the neural substrates underlying essential survival behaviors.

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