Study reveals zebrafish larvae exhibit slowly fluctuating directional swim biases driven by internal dynamics
Researchers found that 5-day-old zebrafish larvae exhibit slowly changing directional swimming preferences over many hours, even in stable, unchanging environments. These fluctuations appear to arise from a non-stationary Markovian process involving two largely independent internal input streams that influence whether the fish repeats its swim direction. The findings challenge classical models that treat individual behavioral biases as constant or externally driven, suggesting intrinsic brain dynamics play a larger role in shaping behavior than previously recognized.
A new preprint study on bioRxiv reports that zebrafish larvae as young as five days old display slowly drifting directional swim biases that unfold over hours, even when kept in homogeneous, stable sensory environments. Using computational modeling, the researchers propose that these fluctuations emerge from a non-stationary Markovian process, in which two largely independent internal input streams modulate the probability of repeating a swim direction from one bout to the next. Crucially, these slow behavioral fluctuations persist across varying sensory conditions — including different light intensities and global motion cues — though the statistical properties of the switching are shaped by those conditions. The work challenges classical sensorimotor models that attribute behavioral variability primarily to external stimuli or treat individual biases as fixed or monotonically changing. Instead, the results point to an intrinsic, context-sensitive source of variability rooted in internal neural dynamics. The authors suggest this framework could help advance understanding of the computational principles underlying spontaneous and adaptive behavior more broadly.
What's missing
As a preprint, this work has not yet undergone peer review, so findings should be interpreted with caution. The study does not identify the specific neural circuits or molecular mechanisms responsible for the two proposed internal input streams. It is also unclear whether these dynamics generalize to older zebrafish, other species, or more naturalistic environments with complex sensory landscapes.
What different sources said
- bioRxivCenter
Non-stationary Markovian dynamics shape swim bias fluctuations in zebrafish larvae
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