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refers to one of two parts of the granular insula reported by some authors in the human. It was defined by automated analysis of images of silver-stained coronal sections ( Kurth-2010a ). It is located between the other part, area Ig2 of Kurth, and the posterodorsal margin of the long insular gyri. Both parts are distinguished by a well-developed internal granular layer (IV). Area Ig1 of Kurth is distinguished from area Ig2 of Kurth by a broader external granular layer (II), a more homogeneous external pyramidal layer (III), and a less distinct internal pyramidal layer (V). A contemporary study in the human conducted manually on the basis of multiple stains did not report subdivision of the granular insula ( Morel-2013 ).
Results of studies in the macaque are also mixed. The area Ig1 of Gallay ( Gallay-2012 ), identified on the basis of multiple stains, showed a similar homogeneity of external pyramidal layer (III) compared to area Ig2 of Gallay, but it differed topologically. It was located rostroventrally to area Ig2 of Gallay, whereas area Ig1 of Kurth was located caudodorsally to area Ig2 of Kurth. Subdivision of the granular insula was not reported in other studies of the macaque ( Mesulam-1984, Paxinos-2009a ), nor of the rat ( Swanson-2004 ) or mouse ( Hof-2000 ).
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