The term area Iai (macaque) refers to the intermediate agranular insular area, a subdivision of the orbitomedial prefrontal cortex (macaque). It is defined on the basis of internal structure and connectivity. Located in the posterior portion of the orbital gyri, area Iai is one of three subdivisions of the lateral agranular insular region. A significant structural feature of area Iai is a thick band of cells in the internal pyramidal layer (V) that are immunoreactive for neurofilament protein (by SMI-32 antibody). The area is also distinguished from some adjacent areas by bands stained for cholinesterase in the middle of the internal pyramidal layer (V) and at the boundary of the multiform layer (VI) with underlying white matter. The other two lateral agranular areas are area Ial (macaque) and area Iapl (macaque) ( Carmichael-1994 ). Its equivalent in the human is area Iai ( Ongur-2003 ). As a component of insulo-orbital cortex, its equivalent in the rat and mouse would be in the agranular insular cortex.