Binocular integration of prey stimuli in the zebrafish visual system

Most animals with two eyes combine the inputs to achieve binocular vision, which can serve numerous functions, and is particularly useful in hunting prey. However, the mechanisms by which visual information from the two eyes are combined remain largely unknown. Here, we designed a device to reversibly occlude the eyes of a head-fixed zebrafish larva, and used large-scale volumetric two-photon imaging to identify binocular neurons that respond to prey stimuli. We found these binocular prey-responsive neurons (bino-PRNs) were primarily located in three areas, the pretectum, thalamus, and nucleus isthmi. We then characterized the bino-PRNs functional properties, and found that their left and right eye receptive fields are offset to varying degrees, which would correspond to objects at naturalistic hunting distances for a larva with converged eyes. We also found that bino-PRNs have a significantly greater response in hunting trials, which could be the result of an eye convergence-related corollary discharge. We then optogenetically induced prey capture eye and tail movements, and found that this hunting command activates prey responsive neurons in the pretectum, thalamus, and nucleus isthmi. These findings indicate that bino-PRNs receive visual and motor input that would allow them to encode prey position in three dimensions.