Good narratives for species justification:

EXAMPLE 1:  The rat is most appropriate animal for numerous reasons. First, to link symptom severity to neuronal activity we must be able to make neural recordings during awake and behaving conditions. The rat is the most often used animal under these circumstances. Second, of the two widely used animal models of Parkinson's Disease (MPTP-monkey and 6-OHDA rat), rat experiments are the more humane. Third, DBS has recently been shown to reverse symptoms in the 6-OHDA rat.1,2