Growing Together and Growing Apart: Regional and Sex Differences in the Lifespan Developmental Trajectories of Functional Homotopy

Abstract

Functional homotopy, the high degree of synchrony in spontaneous activity between geometrically corresponding interhemispheric (i.e., homotopic) regions, is a fundamental characteristic of the intrinsic functional architecture of the brain. However, despite its prominence, the lifespan development of the homotopic resting-state functional connectivity (RSFC) of the human brain is rarely directly examined in functional magnetic resonance imaging studies. Here, we systematically investigated age-related changes in homotopic RSFC in 214 healthy individuals ranging in age from 7 to 85 years. We observed marked age-related changes in homotopic RSFC with regionally specific developmental trajectories of varying levels of complexity. Sensorimotor regions tended to show increasing homotopic RSFC, whereas higher-order processing regions showed decreasing connectivity (i.e., increasing segregation) with age. More complex maturational curves were also detected, with regions such as the insula and lingual gyrus exhibiting quadratic trajectories and the superior frontal gyrus and putamen exhibiting cubic trajectories. Sex-related differences in the developmental trajectory of functional homotopy were detected within dorsolateral prefrontal cortex (Brodmann areas 9 and 46) and amygdala. Evidence of robust developmental effects in homotopic RSFC across the lifespan should serve to motivate studies of the physiological mechanisms underlying functional homotopy in neurodegenerative and psychiatric disorders.

Long‐term acclimatization to high‐altitude hypoxia modifies interhemispheric functional and structural connectivity in the adult brain

“…Methods for symmetric template creation and VMHC computation were consistent with Zuo et al. (2010). All 31 normalized GM images were averaged to create a mean image, which was then averaged with its left–right mirror versions to generate a group‐specific, symmetrical, study‐specific GM template.…”

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Time-Shift Homotopic Connectivity in Mesial Temporal Lobe Epilepsy

“…25 The residual images were further coregistered to a symmetric template according to previous studies. 5,8 The symmetric template was created as follows: First, all participants' normalized gray matter images were averaged to create a mean normalized gray matter template. This template was then averaged with its left-right mirrored version to generate a groupspecific symmetric template.…”

“…This template was then averaged with its left-right mirrored version to generate a groupspecific symmetric template. 5 Finally, we spatially smoothed the images with an 8-mm full width at half maximum isotropic Gaussian kernel.…”

“…On the basis of resting-state functional MR imaging measurements, an approach based on voxel-mirrored homotopic connectivity (VMHC) quantifies the interhemispheric homotopic connections by measuring the functional connectivity between each voxel in 1 hemisphere and its mirrored counterpart. 5 Zuo et al 5 found age-related increases in interhemispheric functional connectivity in the primary sensorimotor areas and de-creases in the higher order processing areas, which provided insight into the evolution of brain development. Studies have also revealed specific alterations of homotopic connection in a cohort of brain diseases.…”