A surface‐based technique for mapping homotopic interhemispheric connectivity: Development, characterization, and clinical application

Abstract

The functional organization of the human brain consists of a high degree of connectivity between inter-hemispheric homologous regions. The degree of homotopic organization is known to vary across the cortex and homotopic connectivity is high in regions that share cross-hemisphere structural connections or are activated by common input streams (e.g. the visual system). Damage to one or both regions, as well as damage to the connections between homotopic regions, could disrupt this functional organization. Here were introduce and test a computationally efficient technique, surface-based Homotopic Inter-hermispheric Connectivity (sHIC), that leverages surface-based registration and processing techniques in an attempt improve the spatial specificity and accuracy of cortical inter-hemispheric connectivity estimated with resting state functional connectivity. This technique is shown to be reliable both within and across subjects. sHIC is also characterized in a dataset of nearly 1000 subjects. We confirm previous results showing increased inter-hemispheric connectivity in primary sensory regions, and reveal a novel rostro-caudal functionally-defined network level pattern of sHIC across the brain. In addition, we demonstrate a structural-functional relationship between sHIC and atrophy of the corpus callosum in multiple sclerosis (r=0.2979, p=0.0461). sHIC presents as a sensitive and reliable measure of cortical homotopy that may prove useful as a biomarker in neurologic disease.

Physical activity is positively related to local functional connectivity in adolescents’ brains

“…The corpus callosum plays a crucial role in interhemispheric functional connectivity, as it is the main white matter structure that connects the brain's hemispheres. Indeed, the properties of the corpus callosum are significantly related to homotopic connectivity (De Benedictis et al, 2016;Mancuso et al, 2019;Tobyne et al, 2016). Despite the demonstrated link between aerobic fitness and the corpus callosum, we did not find a clear evidence of a connection between aerobic fitness and homotopic connectivity.…”

“…The corpus callosum has been shown to play an important role in the interhemispheric exchange of information (van der Knaap & van der Ham, 2011). Specifically, the corpus callosum has been suggested as a significant underlying structure in terms of affecting homotopic connectivity, which refers to functional connectivity among homologous brain locations across the hemispheres (De Benedictis et al, 2016;Mancuso et al, 2019;Tobyne et al, 2016). Despite these similarities, it is not yet known whether physical activity and aerobic fitness also relates to the homotopic functional connectivity of the brain.…”

Functional Integration Between the Two Brain Hemispheres: Evidence From the Homotopic Functional Connectivity Under Resting State

“…They identified the improved precision of this surface-based approach over the previous volume-based flipping method. Following this study, Tobyne et al (2016) further introduced a computationally efficient technique, surface-based HoFC, that leveraged surface-based registration to improve the spatial specificity and accuracy of cortical HoFC under resting state. The surface-based HoFC for each pair of homologous vertices was calculated by using the pairwise Pearson’s correlation between the extracted time series.…”

“…The surface-based HoFC for each pair of homologous vertices was calculated by using the pairwise Pearson’s correlation between the extracted time series. This technique is presented as a sensitive measure of HoFC in the human brain and is proved to be reliable both within and across subjects ( Tobyne et al, 2016 ). Particularly, this method presents a more constrained pattern of HoFC along the medial surface.…”

“…Particularly, this method presents a more constrained pattern of HoFC along the medial surface. As noted, either the volumetric smoothing or greater accuracy of spherical registration techniques might lead to discrepancies between volume-based and surface-based HoFC ( Tobyne et al, 2016 ).…”