Visual Threat Location Impacts Brain-Wide Visual Adaptation Networks.

Habituation is a simple form of nonassociative learning that is characterized by a decrease in response to a repetitive stimulus. As escape responses can be energetically costly and disruptive to normal behavior, it is important that prospective prey learn whether a perceived stimulus is a genuine threat or an innocuous stimulus that they can ignore. In response to a visual looming stimulus, larval zebrafish perform a characteristic escape swim that reliably habituates, and because they are small and transparent, they have been an important model for characterizing brain-wide activity patterns during habituation. In this study, we explore the spatial properties of visual adaptation to gauge whether it is mediated by local, regional, or brain-wide circuits. We present repetitive visual loom stimuli either in a fixed position in visual space or in variable positions, while also performing brain-wide calcium imaging. Across the brain, we identify both neural responses that are specific to looms at particular positions within the visual field and responses that occur regardless of where the loom is presented. By quantifying the degree of adaptation across these responses, we show that brain-wide adaptation occurs more rapidly when the position of the loom remains unchanged and that alternate looms occurring in different parts of the visual field minimally contribute to adaptation for looms at the original position. We found that the tectum, homologous to the superior colliculus, has response profiles and spatial sensitivity indicative of important contributions to this position-specific visual adaptation.