Why tree shrews?

Tree shrews are highly visual, diurnal animals that are approximately the size of rats. They are not primates, but they are more closely related to primates than rodents or cats. The visual system of a tree shrew is more similar to ours than that of a rodent, including cone dominent retinae, a visual cortex that is organized into functional columns, and a large fraction of cortex devoted to visual form processing.

The field of neuroscience is exploding with the development of exciting, new technologies that allow us to monitor and manipulate neural activity as well as determine how neurons are connected together. Tree shrews are well-suited for many of those applications.