Zebrafish Light-Dark Preference (Scototaxis)

The light-dark preference test, or scototaxis assay, exploits the natural preference of adult zebrafish for dark environments to quantify anxiety-like behavior. The apparatus consists of a rectangular tank with one half illuminated and the other half covered or painted black, creating a clear boundary between light and dark compartments. This dark preference is mediated by the lateral habenula and dorsal telencephalic pallium, homologous to the mammalian limbic system, with GABAergic neurons in the ventral telencephalon modulating approach-avoidance decisions at the light-dark boundary. Unlike rodent light-dark paradigms where dark preference reflects safety-seeking, zebrafish scototaxis is one of the most pharmacologically validated anxiety measures in fish, with anxiolytic drugs consistently increasing light-zone exploration.

The primary dependent variable is the percentage of time spent in the light compartment, with untreated adult zebrafish typically spending 20-35% of a 10-minute session in the illuminated zone. Secondary measures include the number of light-dark transitions (reflecting exploratory drive and risk-taking), latency to first entry into the light zone, mean duration per light visit, and the spatial distribution of position relative to the boundary. Average distance from the light-dark border provides a continuous measure of approach-avoidance conflict, while within-session temporal analysis reveals habituation to the light zone over successive minutes.

ConductMaze defines the light-dark boundary from calibrated arena coordinates and classifies each tracked position into light or dark compartment in real time using overhead camera tracking. The system computes compartment occupancy ratios, transition frequencies, boundary-proximity histograms, and per-minute time-course analyses. Automated light-zone bout analysis segments each visit to extract visit frequency, mean bout duration, and maximum penetration depth into the light zone.