The term nucleus incertus refers to a group of cells located dorsomedially in the pontine tegmentum of the rat ( Swanson-2004 ) and the mouse ( Hof-2000 ). In the rat it is composed of two parts, the compact part of nucleus incertus and the diffuse part of nucleus incertus ( Swanson-1998 ). Some authors refer to the area as a subdivision of the pontine central gray ( Paxinos-2009b ). Functionally it is one of the raphe nuclei (functional) in the behavioral state system ( Swanson-2004 ).