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Connectivity-based parcellation reveals interhemispheric differences in the insula


The aim of this work was to use probabilistic diffusion tractography to examine the organization of the human insular cortex based on the similarities of its remote projections. Forty right-handed healthy subjects (33.8 ± 12.7 years old) with no history of neurological injury were included in the study. After the spatial standardization of diffusion tensor images, insular cortical masks were delineated based on the Harvard–Oxford Cortical Atlas and were used to initiate fibertracking. Cluster analysis by the k-means algorithm was employed to partition the insular voxels into two groups that featured the most distinct distribution of connections. In order to perform volumetric comparisons, the assigned label maps were transformed back to space of the subjects’ native anatomical MR images. The outlines of the change in connectivity profile did not respect the known cytoarchitectural subdivisions and were shown to be independent from the gyral anatomy. Interhemispheric asymmetry in the volumes of connectivity-based subdivisions was observed putatively marking a leftward functional dominance of the anterior insula and its reciprocally interconnected targets which influences the size of insular area where similar connections are represented. The fractional anisotropy values were not significantly different between the hemipsheres or connectivity-based clusters; however, the mean diffusivity was higher in the anterior insula in both hemispheres.

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The authors gratefully acknowledge the technical support of Saad Jbabdi (Centre for Functional Magnetic Imaging of the Brain, University of Oxford).

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Correspondence to András Jakab.

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Supplementary Fig. 1. Intersubject variability of DTI connectivity-based clustering of the insular cortex. 3D surfaces were generated by accessing the 95th, 90th, 50th, 10th and 5th percentile volumes of each cluster assignment across the population (n = 40). Major anatomical landmarks have been illustrated (for description, see Fig. 3.). (TIFF 576 kb)


Supplementary Fig. 2. Three-way segmentation of the insula based on its structural connectivity patterns. Visualization with a cross-sectional image of the MNI152 T1-weighted image template and 3D surfaces generated using the label asssignments. Major anatomical landmarks have been illustrated (for description, see Fig. 3.). Red object: anterior insula (AI’), teal object: dorsomedial insula (MI), blue object: posterior insula (PI). (TIFF 784 kb)

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Jakab, A., Molnár, P.P., Bogner, P. et al. Connectivity-based parcellation reveals interhemispheric differences in the insula. Brain Topogr 25, 264–271 (2012).

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  • Insula of reil
  • Cerebral cortex
  • Diffusion tensor imaging
  • Diffusion magnetic resonance imaging