Lin, M. K. et al. eLife 8, e40042 (2019).

Connectivity maps of the brain serve as a template for functional and behavioral studies, as exemplified by the maps available for the mouse brain. Lin et al. now outline a histological and computational pipeline for generating such a connectivity map for the marmoset brain. Marmosets are New World monkeys that are attractive as models because of their social behaviors, their small brain size, and the availability of molecular tools. The standardized workflow for mapping the marmoset brain involves in vivo magnetic resonance imaging (MRI) of the brain, injections of anterograde and retrograde tracers into multiple brain regions in a grid-like pattern, ex vivo MRI, and cryo-sectioning of the brain. The brain sections are then subjected to various staining procedures followed by imaging. The acquired images are registered to each other and to a reference brain atlas. The whole pipeline takes about one month for a single brain. The researchers expect that at the current processing rate, the connectivity map for the marmoset brain will be completed by 2024, although collaborative efforts would speed this up.