The term mediane Zone (Formatio reticularis) refers to one of three parts of the reticular formation of the brainstem subdivided longitudinally on the basis of histochemical stains for neurotransmitters and related enzymes, connectivity, cytoarchitecture and function as well as conventional stains for Nissl substance and myelin. It is located in the very midline of the brainstem and includes the many raphe nuclei (histological) whose neurons are predominantly serotonergic. The other parts are the mediale magnozellulare Zone (Formatio reticularis) and the laterale parvozellulare Zone (Formatio reticularis) ( Schiebler-1999 ).