Bulk Dye Loading for In Vivo Calcium Imaging of Visual Responses in Populations of Tectal Neurons.

Bulk loading of neurons with fluorescent calcium indicators in transparent albino tadpoles offers a rapid and easy method for tracking sensory-evoked activity in large numbers of neurons within an awake developing brain circuit. In vivo two-photon time-lapse imaging of an image plane through the optic tectum allows defining receptive field properties from visual-evoked responses for studies of single-neuron and network-level encoding and plasticity. Here, we describe loading the tadpole optic tectum with the membrane-permeable AM ester of Oregon Green 488 BAPTA-1 (OGB-1 AM) for in vivo imaging experiments.