Reduction of visual stimulus artifacts using a spherical tank for small, aquatic animals

Abstract

Delivering appropriate stimuli remains a challenge in vision research, particularly for aquatic animals such as zebrafish. Due to the shape of the water tank and the associated optical paths of light rays, the stimulus can be subject to unwanted refraction or reflection artifacts, which may spoil the experiment and result in wrong conclusions. Here, we employ computer graphics simulations and calcium imaging in the zebrafish optic tectum to show, how a spherical glass container optically outperforms many previously used water containers, including Petri dish lids. We demonstrate that aquatic vision experiments suffering from total internal reflection artifacts at the water surface or at the flat container bottom may result in the erroneous detection of visual neurons with bipartite receptive fields and in the apparent absence of neurons selective for vertical motion. Our results and demonstrations will help aquatic vision neuroscientists on optimizing their stimulation setups.

Spherical arena reveals optokinetic response tuning to stimulus location, size, and frequency across entire visual field of larval zebrafish

“…We additionally designed the setup to minimise visual obstruction and developed a new embedding technique to immobilise the larva at the tip of a narrow glass triangle (see Materials and methods). In almost all possible positions, fish can thus perceive stimuli without interference ( Wang et al, 2021 ). The distance between most of the adjacent LED pairs is smaller than the photoreceptor spacing in the larval retina ( Haug et al, 2010 ; Tappeiner et al, 2012 ), resulting in a good spatial resolution across the majority of the spherical arena surface ( Figure 1—figure supplement 2 , see Materials and methods section on resolution).…”

A robust receptive field code for optic flow detection and decomposition during self-motion

“…This reservoir was placed in the centres of the LED arena, whose radius was >9 times larger than the radius of the reservoir. Because the optic flow stimuli were all symmetric to the horizontal plane, we do not expect any strong disturbance from internal reflection to animal behaviour as discussed in a previous paper 50 . A selected fish was then placed in the reservoir filled with E3 medium.…”

Spatiotemporal visual statistics of aquatic environments in the natural habitats of zebrafish

“…2a of 22 ), showing that the OMR was drastically reduced for spatial frequencies of 0.08 cycles/degree or higher presented on a display. However, an aquatic visual stimulus setup with flat water container surfaces was used in this study, which introduces stimulus distortions such that the stimulus appears different to the fish than intended by the experimenter 23 , 24 . Based on the estimated distance from fish to water container bottom (0.25 cm, personal communication Jiaheng Xie), the distance from water container to stimulus screen (5.65 cm) and the estimated thickness of the water container and transparent stage (0.5 cm) in this study, we calculated the spatial frequency visible to the fish at the nadir based on the equations in Appendix 1 of Dunn et al 23 .…”