Probabilistic tractography recovers a rostrocaudal trajectory of connectivity variability in the human insular cortex

• Published in: Human brain mapping 2012-09, Vol.33 (9), p.2005-2034
• Main Authors: Cerliani, Leonardo, Thomas, Rajat M., Jbabdi, Saad, Siero, Jeroen C.W., Nanetti, Luca, Crippa, Alessandro, Gazzola, Valeria, D'Arceuil, Helen, Keysers, Christian
• Format: Article
• Language: English
• Subjects: Adult; Biological and medical sciences; Brain Mapping; Cerebral Cortex - anatomy & histology; Cerebral Cortex - physiology; connectivity-based parcellation; Diffusion Tensor Imaging; diffusion-weighted imaging; DTI; Ear and associated structures. Auditory pathways and centers. Hearing. Vocal organ. Phonation. Sound production. Echolocation; Functional Laterality; Fundamental and applied biological sciences. Psychology; Humans; Image Processing, Computer-Assisted; insula; Investigative techniques, diagnostic techniques (general aspects); laplacian eigenmaps; Male; Medical sciences; Middle Aged; Models, Statistical; Nerve Fibers - physiology; Nervous system; Neural Pathways - anatomy & histology; Neural Pathways - physiology; Radiodiagnosis. Nmr imagery. Nmr spectrometry; Vertebrates: nervous system and sense organs
• ISSN: 1065-9471; 1097-0193
• DOI: 10.1002/hbm.21338

The insular cortex of macaques has a wide spectrum of anatomical connections whose distribution is related to its heterogeneous cytoarchitecture. Although there is evidence of a similar cytoarchitectural arrangement in humans, the anatomical connectivity of the insula in the human brain has not yet been investigated in vivo. In the present work, we used in vivo probabilistic white‐matter tractography and Laplacian eigenmaps (LE) to study the variation of connectivity patterns across insular territories in humans. In each subject and hemisphere, we recovered a rostrocaudal trajectory of connectivity variation ranging from the anterior dorsal and ventral insula to the dorsal caudal part of the long insular gyri. LE suggested that regional transitions among tractography patterns in the insula occur more gradually than in other brain regions. In particular, the change in tractography patterns was more gradual in the insula than in the medial premotor region, where a sharp transition between different tractography patterns was found. The recovered trajectory of connectivity variation in the insula suggests a relation between connectivity and cytoarchitecture in humans resembling that previously found in macaques: tractography seeds from the anterior insula were mainly found in limbic and paralimbic regions and in anterior parts of the inferior frontal gyrus, while seeds from caudal insular territories mostly reached parietal and posterior temporal cortices. Regions in the putative dysgranular insula displayed more heterogeneous connectivity patterns, with regional differences related to the proximity with either putative granular or agranular regions. Hum Brain Mapp 33:2005–2034, 2012. © 2011 Wiley Periodicals, Inc.