The term field G refers to a narrow strip of 'hypergranular' neocortex located along the dorsal and caudal boundaries of the insula in the human ( Morel-2013 ) and the macaque ( Gallay-2012 ). It is located between the opercula, namely the frontoparietal operculum and the most caudal part of the temporal operculum, and the dysgranular insula and granular insula. Most authors regard it as representing extensions of architectonically defined areas of the cerebral cortex, such as the primary somatosensory cortex and secondary somatosensory cortex, across the limiting sulcus into the insula ( Mesulam-1982 ). The limiting sulcus, which defines the outer boundary of the field, is not present in the rat ( Swanson-2004 ) or the mouse ( Hof-2000 ).