Whole-brain mapping in adult zebrafish and identification of the functional brain network underlying the novel tank test

Zebrafish have gained prominence as a model organism in neuroscience over
the past several decades, generating key insight into the development and
functioning of the vertebrate brain. However, techniques for whole brain
mapping in adult stage zebrafish are lacking. Here, we describe a pipeline
built using open-source tools for whole-brain activity mapping in adult
zebrafish. Our pipeline combines advances in histology, microscopy, and
machine learning to capture cfos activity across the entirety of the
brain. Following tissue clearing, whole brain images are captured using
light-sheet microscopy and registered to the recently created adult
zebrafish brain atlas (AZBA) for automated segmentation. By way of
example, we used our pipeline to measure brain activity after zebrafish
were subject to the novel tank test, one of the most widely used behaviors
in adult zebrafish. Cfos levels peaked 15 minutes following behavior and
several regions, including those containing serotoninergic and
dopaminergic neurons, were active during exploration. Finally, we
generated a novel tank test functional brain network. This revealed that
several regions of the subpallium form a cohesive sub-network during
exploration. Functional interconnections between the subpallium and other
regions appear to be mediated primarily by ventral nucleus of the ventral
telencephalon (Vv), the olfactory bulb, and the anterior part of the
parvocellular preoptic nucleus (PPa). Taken together, our pipeline enables
whole-brain activity mapping in adult zebrafish while providing insight
into neural basis for the novel tank test.