The term rostral linear nucleus of the raphe (LIRr) refers to one of two parts of the linear nucleus of the raphe (LIR) in the ventral midbrain tegmentum (MBT). It is located in the midline, dorsal to the interfascicular nucleus and the interpeduncular nucleus at the level of the red nucleus. In the human ( Paxinos-1990a ) and the macaque ( Paxinos-2009a ). Identified by acetylcholinesterase stain, it is located in the midline caudally but extends dorsolaterally above the red nucleus rostrally. Authors who define raphe nuclei in the human on the basis of stains for serotonin synthesis do not classify the rostral nucleus with the raphe nuclei (functional) ( Hornung-2012 ). In the rat ( Swanson-2004 ), and the mouse ( Paxinos-2001 ) it is located in the midline for its full extent.The other component of the LIR is the caudal linear nucleus of the raphe. Functionally both are parts of the behavioral state system ( Swanson-2004 ).