Modular architectonic organization of the insula in the macaque monkey

• Published in: Journal of comparative neurology (1911) Vol. 522; no. 1; pp. 64 - 97
• Main Authors: Evrard, Henry C., Logothetis, Nikos K., (Bud) Craig, A.D.
• Format: Journal Article
• Language: English
• Published: United States Blackwell Publishing Ltd 01-01-2014; Wiley Subscription Services, Inc
• Subjects: Animals; Cerebral Cortex - anatomy & histology; emotion; Female; homeostasis; interoception; Macaca fascicularis; Male; Neural Pathways - anatomy & histology; Neuroanatomical Tract-Tracing Techniques; spino-thalamo-cortical pathway; Thalamus - anatomy & histology; homeostasis; emotion; interoception; spino-thalamo-cortical pathway
• ISSN: 0021-9967; 1096-9861
• DOI: 10.1002/cne.23436

ABSTRACT
In order to provide a framework for ongoing analyses of the neuronal connections of the insular cortex of the macaque monkey using modern high‐resolution methods, we examined its anatomical organization in serial coronal sections stained alternately with Nissl and Gallyas (myelin) techniques. We observed the same 15 distinct architectonic areas in 10 brains. Within the granular, dysgranular, and agranular regions described in prior studies, we identified 4, 4, and 7 distinct areas, respectively. Across brains, these areas have consistent architectonic characteristics, and in flat map reconstructions they display a consistent topological or neighborhood arrangement, despite variations in the size of individual areas between cases. The borders between areas are generally rather sharply defined. Some areas, in particular the dysgranular areas, appear to consistently contain subtle transitions that suggest possible subareas or modules within the well‐delimited areas. The presence of a distinct granular area that straddles the fundus of the superior limiting sulcus over its entire posterior‐to‐anterior extent is consistent with the available evidence on interoceptive thalamocortical projections, and also with the tensile anchor theory of species‐specific cortical gyrification. These observations are consonant with the model of homeostatic afferent processing in the primate insula, and they suggest that discrete modules within insular cortex provide the basis for its polymodal integration of all salient activity relevant to ongoing emotional behavior. J. Comp. Neurol. 522:64–97, 2014. © 2013 Wiley Periodicals, Inc.
The authors show that the classical granular, dysgranular, and agranular sectors of the macaque insula contain 4, 4, and 7 cyto‐ and myelo‐architectonic areas, respectively. These sharply defined and highly consistent areas provide a novel anatomical framework for the examination of the connectional and functional modularity of the primate insula