title: Probabilistic tractography recovers a rostrocaudal trajectory of connectivity variability in the human insular cortex.
abstract: 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.
authors.affiliation: BCN NeuroImaging Center, University of Groningen, A. Deusinglaan, 2-9713AW Groningen, The Netherlands. leonardo.cerliani@gmail.com
authors.forename: Leonardo
authors.initials: L
authors.lastname: Cerliani
authors.forename: Rajat M
authors.initials: RM
authors.lastname: Thomas
authors.forename: Saad
authors.initials: S
authors.lastname: Jbabdi
authors.forename: Jeroen C W
authors.initials: JC
authors.lastname: Siero
authors.forename: Luca
authors.initials: L
authors.lastname: Nanetti
authors.forename: Alessandro
authors.initials: A
authors.lastname: Crippa
authors.forename: Valeria
authors.initials: V
authors.lastname: Gazzola
authors.forename: Helen
authors.initials: H
authors.lastname: D'Arceuil
authors.forename: Christian
authors.initials: C
authors.lastname: Keysers
mesh_terms: D000328:Adult; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000033:anatomy & histology / Q000502:physiology*; D056324:Diffusion Tensor Imaging; D007839:Functional Laterality; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D009412:Nerve Fibers / Q000502:physiology; D009434:Neural Pathways / Q000033:anatomy & histology / Q000502:physiology*