FIGURE 1

Dark-light preference behavior is statistically significant but highly variable impeding assessment of vision loss and recovery after light lesion. (A) Scheme of the dark-light preference setup. The individual compartments of the custom-made arena consist of infrared-transparent material. One half is made from clear, the other half made from black plastic establishing a light and dark zone, respectively. The test fish can freely swim within the whole compartment, which can be illuminated with white light from the top (85 lux). In addition, the arena is illuminated from an infrared light source located beneath the arena and recorded from the top using an infrared-sensitive camera. (B) Quantification reveals that the time fish spent in the light zone is significantly higher in the light off condition (53.6 ± 16.1%) compared to the light on condition (32.9 ± 22.7%). Quantifications of the distance moved (C) and the corresponding velocity (D) show that the fish swam significantly less (light off: 2060 ± 683 cm; light on: 1537 ± 543 cm) and slower (light off: 4.2 ± 0.9 cm/s; light on: 2.7 ± 0.9 cm/s) in illuminated condition. (E) Experimental timeline. Dark-light preference recordings were performed in light on and light off conditions prior to light lesion as well as in light on conditions at 1, 3, 7, 14, and 28 days post lesion (dpl). (F) Quantification of the time spent in the light zone reveals that fish do not change their preference for the dark or light zone after light lesion (light off: 54.3 ± 19.5%, light on: 38.9 ± 23.4%, 1 dpl: 41.9 ± 22.1%, 3 dpl: 41.8 ± 24.9%, 7 dpl: 39.3 ± 22.2%, 14 dpl: 43.6 ± 20.9%, 28 dpl: 56.3 ± 16.6%). Similarly, quantifications of the distance moved (G) and velocity (H) show no lesion-dependent alterations. Statistics: all data are represented as mean ± SD, unpaired t-test (B–D), one-way ANOVA with Dunnett’s multiple comparison test against control (F–H), p < 0.05 (*); 0.01 (**); 0.001 (***) or 0.0001 (****).