The term posterior part of the medial amygdalar nucleus refers to the more caudal component of the medial amygdalar nucleus as identified by Nissl stain; the other is the anterior part of the medial amygdalar nucleus. In the human ( Mai-1997 ) and the macaque ( Amaral-1992 ) it is located deep to the entorhinal sulcus on the medial aspect of the temporal lobe. It is bounded dorsally by the substantia innominata, laterally by the central amygdalar nucleus, ventrolaterally by the basomedial nucleus of the amygdala and ventromedially by the posterior periamygdalar cortex. Some authors report that, in the macaque, the anterior amygdalar area extends almost to the posterior extreme of the amygdala ( Paxinos-2009 ); by their interpretation this area, instead of substantia innominata, forms the dorsal boundary of the nucleus; according to this parcellation the nucleus itself extends further caudally, where its ventromedial border is formed by the amygdalohippocampal area. In the rat ( Swanson-2004 ) and the mouse ( Hof-2000 ) the posterior part of the medial nucleus has three components: the posterodorsal part of the medial amygdalar nucleus, the posteroventral part of the medial amygdalar nucleus and the nucleus of the accessory olfactory tract. caudal to the anterior part of the medial amygdalar nucleus and ventrolateral to the optic tract it is bounded laterally and ventrally by the same structures as in the primate including, according to some authors, the amygdalohippocampal area at its caudal extreme ( Paxinos-2009b; Franklin-2008 ). In the Functional nervous system all parts of the medial amygdalar nucleus are classified in the extended striatum ( Swanson-2004 ).