Dumon, Edouard; (2025) How the brainstem controls the diverse locomotor repertoire of the larval zebrafish. Doctoral thesis (Ph.D), UCL (University College London).

Text Dumon_Thesis Corrected.pdf - Accepted Version Access restricted to UCL open access staff until 1 December 2026. Download (33MB)

Abstract

Locomotion in vertebrates requires the production of a diverse repertoire of movements modulated by sensory cues. The brainstem plays a crucial role in supplying the descending commands underlying this behavior to spinal locomotor circuits, yet it remains unclear what information these commands convey, and how they arise from brainstem neuronal population activity. To tackle these questions, I studied supraspinal locomotor control in the larval zebrafish. Using 2-photon functional calcium imaging, I recorded neural activity in the brainstems of larvae while they produced diverse visually evoked swims. To map swim-related neural activity in my imaging volume, I examined the pixel-wise correlation of fluorescence with swim-vigor-derived regressors. I identified widespread and anatomically patterned swim-related activity in the ventral half of the brainstem. To identify the key descriptors of locomotor behavior diversity in head tethered fish, I analyzed data pooled from 23 fish, and found that most fish shared an 8- dimensional behavioral distribution, which was described by high-level swim kinematics, and differentially sampled by visual stimuli. I therefore investigated the visuomotor tuning properties of brainstem neurons in various stimulus contexts, and found that swim-tuned brainstem loci displayed a striking diversity of stimulus-specific tuning patterns. To identify neural correlates of locomotor behavior, I then built maps of the correlation of brainstem neuronal activity with swim kinematics and identified a previously unknown locus encoding swim vigor, and an anatomically patterned population of neurons in the ventral hindbrain encoding the power spectrum of tail oscillations. Finally, to investigate the neural substrates of brainstem locomotor commands, I built linear decoding models of swim kinematics. By examining the tuning and encoding properties of neurons highly predictive of behavior, I provided supportive evidence for a spectral representation of tail movement in the ventral hindbrain, as well as the coexistence of different control paradigms within the brainstem locomotor control circuitry.

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