From dusk till dawn – How zebrafish respond to changes in illumination

Larval zebrafish show several innate responses to spatial and temporal changes in illumination, from rapid orientation and taxis to sustained modulation of locomotor activity. However, little is known about the underlying neural circuits and how neuromodulators act on them to alter locomotor behavior. Using high-speed video tracking in a custom-built arena we quantitatively assess the fishes’ choice of swimming behavior in response to visual stimuli such as whole field luminance changes and local light and dark patches. We aim to determine the neural activity evoked by the same stimuli using in vivo calcium imaging of transgenic fish expressing genetically encoded calcium indicators. In parallel, we are building a library of short promoter sequences that target expression to distinct neuronal types, with the aim of developing a comprehensive set of transgenic driver lines. These can be combined with different reporter lines to optogenetically activate or silence these populations, and record activity in freely swimming fish using GFP-Aequorin.