The term prefrontal cortex refers to the large rostral part of the frontal lobe in primate. Defined on the basis of internal structure, it is six-layered granular and dysgranular neocortex. It is composed of lateral prefrontal cortex, orbital prefrontal cortex, and medial prefrontal cortex. The lateral prefrontal cortex is commonly divided into dorsolateral prefrontal cortex and ventrolateral prefrontal cortex; and the medial prefrontal cortex is divided into dorsomedial prefrontal cortex and ventromedial prefrontal cortex. All are found in the human and the macaque. Historically, application of the term ‘prefrontal cortex’ has varied greatly. Before 2020 the most inclusive definition for the human, based on architectonic segmentations by several authors, included all of Brodmann's frontal region (areas 9-12 and 44-47) and the three most rostral areas of Brodmann's cingulate region (24, 25, and 32) ( Zilles-2012 ). The macaque equivalent was prefrontal cortex (Walker). According to those definitions the prefrontal cortex occupied all of the frontal lobe rostral to the premotor cortex. From mid-2020, the NeuroNames ontology and standard nomenclature will be based upon the multimodal segmentation developed in the human Connectome Project ( Glasser-2016 ). That segmentation includes the same regions with the exception of the anterior cingulate cortex ( Vogt-2012 ), the current equivalent of Brodmann's areas 24,25 and 32. Many authors have restricted application of the term 'prefrontal' to fewer areas. Brodmann himself applied it only to area 11 of Brodmann (human). Many have included only his frontal region in the definition ( Anthoney-1994 ), or only Brodmann's parcellation of the orbital gyri ( Crosby-1962 ), or only areas of the lateral prefrontal cortex of the frontal lobe located rostral to the motor cortex ( Petrides-2012 ). Most prefrontal cortical areas are of granular cortex or dysgranular cortex, which are unique to the frontal areas rostral to the agranular motor cortex of primate ( Zilles-2012 ). In the rat, the cerebral cortex located most rostrally, that is, at the frontal pole, is motor cortex and lacks an internal granular layer, Layer IV ( Swanson-2004 ). The rat, and presumably the mouse, have areas near the frontal pole that are cytoarchitecturally equivalent to a very narrow band of agranular cortex at the posterior margin of the primate orbital gyri. Continuous with agranular insular cortex, that area is the agranular insula of the orbital prefrontal cortex. Like the granular lateral prefrontal cortex, most of orbital prefrontal cortex is granular and has no equivalent in the rat ( Preuss-1995; Wallis-2012 ).Thus, while a PubMed search for articles with keywords 'prefrontal cortex in rat' results in a list of more than 8,000 citations, brain atlases of the rat ( Swanson-2004, Paxinos-2009b ) and mouse ( Franklin-2008; Hof-2000 ) do not show an area by that name. Based on those observations and reviews by Preuss-1995 and Wallis-2012, the NeuroNames ontology does not contain a rodent equivalent for primate prefrontal cortex.