Poster abstracts
Poster number 62 submitted by Lindsay Anderson
Uncovering the modulatory role of the nucleus of the medial longitudinal fasciculus in inducing swimming speed in zebrafish during thermoregulatory behaviors
Lindsay Anderson (Neuroscience Graduate Program, The Ohio State University College of Medicine), MartinHaesemeyer (Neuroscience Graduate Program, The Ohio State University College of Medicine)
Abstract:
Animals must rapidly adapt to environmental changes through behavioral flexibility, requiring precise integration of sensory inputs and motor outputs. In zebrafish, the nucleus of the medial longitudinal fasciculus (nMLF) is a key sensorimotor circuit modulating locomotor speed, from slow exploration to fast escape responses. Excitatory spinal-projecting neurons in the nMLF exhibit behavior-specific recruitment, with some active during sustained swimming and others during sudden movements. These neurons also extend axonal collaterals to the caudal brainstem, potentially fine-tuning swim speeds in response to sensory stimuli. While vestibular and visual inputs to the nMLF have been studied, discrepancies in its functional diversity suggest additional roles, particularly in thermoregulation, a critical behavior for maintaining preferred body temperatures. We have identified a brainstem thermoregulatory circuit encoding specific swim behaviors, including speed modulation, raising the question of whether the nMLF and brainstem circuits work in parallel to optimize thermoregulatory navigation. This study aims to: (1) identify temperature-sensitive afferent inputs to the nMLF using spinal backfills, functional calcium imaging, and photo-activatable-GFP tracing in temperature-responsive forebrain regions; (2) determine how nMLF activity integrates thermosensory inputs to drive locomotor behaviors through two-photon guided patch clamp recordings and fictive swimming assays; and (3) evaluate the role of nMLF-brainstem interactions in achieving peak swim speed by ablating nMLF-brainstem projections, performing whole-brain functional imaging, and assaying free-swimming zebrafish in a thermal gradient. I hypothesize the nMLF integrates thermosensory inputs and modulates inhibitory-excitatory interactions to regulate brainstem-driven locomotor output, enabling adaptive swim speeds during thermoregulatory navigation and exploratory or avoidance behaviors. This work will advance our understanding of how neural circuits anticipate environmental changes and drive adaptive behaviors, providing a model for sensory-motor integration. These findings will elucidate the neural basis of behavioral flexibility and its relevance to survival in dynamic environments.
References:
1. Berg, E.M., Mrowka, L., Bertuzzi, M., Madrid, D., Picton, L.D., and El Manira, A. (2023). Brainstem circuits encoding start, speed, and duration of swimming in adult zebrafish. Neuron 111, 372-386.e4. doi.org/10.1016/j.neuron.2022.10.034.
Keywords: Sensorimotor, Behavior, Neural Circuits