Connectivity-based parcellation reveals interhemispheric differences in the insula

Abstract

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.

Reflections of word processing in the insular cortex: A sub-regional parcellation based functional assessment

“…More specifically, the employment of detailed multi-modal parcellation maps to assess sub-regional sensitivity appears to provide a much more accurate understanding of the relationship between component-specific functional activations and underlying anatomical structures, such that this cluster sensitivity seems to reflect cytoarchitectonic subdivisions of the anterior insular cortex into the more dorsal dysgranular area more involved in attention-shift and control processing, and the more ventral agranular part rather involved for homeostatic and emotion regulation (Lamm & Singer, 2010;Mesulam & Mufson, 1982). Finally, the hemispheric difference in activation gradient of the left and right anterior insula reported here points towards a hemispheric asymmetry in the volume of connectivity-based subdivisions found by a recent probabilistic diffusion tractographic study, which reports a strong leftward functional dominance of the anterior insula, compared to the right, and its reciprocally interconnected targets (Jakab, Molnar, Bogner, Beres, & Berenyi, 2012).…”

Multimodal investigation of epileptic networks

“…The middle insular cortex has connections with frontal (superior, inferior, and precentral), parietal (postcentral and supramarginal), and temporal (inferior and superior) gyri. Finally, the posterior insular cortex has connections with frontal (superior, inferior, and precentral), parietal (postcentral), and temporal (inferior and superior) gyri and with the putamen (Cerliani et al, 2012;Cloutman et al, 2012;Jakab et al, 2012). These results are in accordance with tract-tracing studies but some connections in primates were not found in humans.…”

Comparison of structural covariance with functional connectivity approaches exemplified by an investigation of the left anterior insula

“…Indeed there is some evidence for this, as anatomical tracer studies in monkeys found strong reciprocal interconnectivity between the AI and various limbic regions including the orbitofrontal cortex, temporal pole and amygdala (Mesulam and Mufson, 1982; Mufson and Mesulam, 1982). Noninvasive diffusion imaging of the human insula similarly identified anatomical connections the AI with orbitorfrontal, temporal, and inferior frontal regions (Cloutman et al, 2012; Jakab et al, 2012) as well as with the amygdala (Cerliani et al, 2012). While these studies did not observe particular anatomical connectivity between the AI and midline regions that was prominent in our SC pattern, remarkably strong anatomical connectivity (but no RS functional connectivity) between the insula and medial frontal gyrus as well as the PCC was reported by (Skudlarski et al, 2008).…”