Heritable natural variation of light/dark preference in an outbred zebrafish population

Larval zebrafish display dynamic learning of aversive stimuli in a constant visual surrounding

“…Two previous studies employing the same light/dark preference paradigm fail to observe consistent behavioral changes within and across trials (Dahlén et al, 2019;Wagle et al, 2017). This is likely due to the fact that stimulus learning results in small but significant changes while displaying individual differences, making it difficult to detect with a small sample size.…”

“…Previous studies have shown that while individual variability exists, larval zebrafish generally find the dark more aversive than the light environment, and the center more aversive than the periphery of the arena. These preferences likely reflect anti-predatory responses (Bai et al, 2016;Dahlén et al, 2019;Prut and Belzung, 2003;Schnörr et al, 2012;Treit and Fundytus, 1988;Wagle et al, 2017). Both types of behavioral responses could potentially be subjected to non-associative learning, resulting in short-and long-term memories that modify the original responsiveness to aversive stimuli.…”

“…All data analysis was performed with custom code written in Python (Supplemental code). The Light/Dark Choice Index (LD-CI) and Periphery-Center Choice index (PC-CI) was calculated using the equations described in Dahlén et al(2019) ( Figure 1B ). Increase of each index indicates an increased time an animal spent in the area to which it was initially aversive (i.e.…”

“…At 6dpf, dishes with individualized larvae were first moved to a same blue pad (luminance = 298 lux) in the behavior room one hour before test (pre-adaptation). Each larva was characterized for its light/dark preference and periphery/center preference (a.k.a thigmotaxis) with a previously established paradigm (Bai et al, 2016; Dahlén et al, 2019; Lau et al, 2011; Wagle et al, 2017). Briefly, an individual was transferred to a behavior chamber (4cm (L) × 4 cm (W) × 1.5 cm (H)) that was evenly divided into a light and a dark compartment by an opaque tape applied to the outside wall ( Figure 1A, top panel ).…”

“…Larval zebrafish display distinct motor behaviors that are sensitive to the intensity of both pre-adapted and current photic stimuli (Burgess et al, 2010; Burgess and Granato, 2007; Facciol et al, 2019). In our paradigm with well-controlled luminance history and constant visual surrounding, larval zebrafish generally display dark avoidance and center avoidance (also known as thigmotaxis) with heritable individual variability and are considered fear or anxiety-related (Bai et al, 2016; Dahlén et al, 2019; Schnörr et al, 2012; Steenbergen et al, 2011; Wagle et al, 2017). From an ethological perspective, the extent of avoidance is likely a readout of the circuitry that balances anti-predation (i.e., avoid the dark and the center) and free exploration (i.e., approach the dark and the center).…”