The term extended amygdala refers to a composite structure of the endbrain that is defined by connectivity and neurochemical staining. In the human ( Heimer-1995 ) and the macaque ( Paxinos-2009a ) it includes the central amygdalar nucleus and a portion of the corticomedial nuclear group of the amygdala, the portion of substantia innominata just beneath the globus pallidus and putamen, the medial portion of nucleus accumbens, and the nuclei of stria terminalis. The boundaries are indistinct in Nissl stained sections ( Heimer-1995 ). It is also found in the rat (Linley-2017 ) and mouse ( Macinkiewvcz-2016 ).