Abstract
Introduction: There are still uncertainties about the true nature of age related changes in topological properties of the brain functional network and its structural connectivity during various developmental stages. In this cross- sectional study, we investigated the effects of age and its relationship with regional nodal properties of the functional brain network and white matter integrity.Method: DTI and fMRI data were acquired from 458 healthy Chinese participants ranging from age 8 to 81 years. Tractography was conducted on the DTI data using FSL. Graph Theory analyses were conducted on the functional data yielding topological properties of the functional network using SPM and GRETNA toolbox. Two multiple regressions were performed to investigate the effects of age on nodal topological properties of the functional brain network and white matter integrity.Result: For the functional studies, we observed that regional nodal characteristics such as node betweenness were decreased while node degree and node efficiency was increased in relation to increasing age. Perversely, we observed that the relationship between nodal topological properties and fasciculus structures were primarily positive for nodal betweenness but negative for nodal degree and nodal efficiency. Decrease in functional nodal betweenness was primarily located in superior frontal lobe, right occipital lobe and the global hubs. These brain regions also had both direct and indirect anatomical relationships with the 14 fiber bundles. A linear age related decreases in the Fractional anisotropy (FA) value was found in the callosum forceps minor.Conclusion: These results suggests that age related differences were more pronounced in the functional than in structural measure indicating these measures do not have direct one-to-one mapping. Our study also indicates that the fiber bundles with longer fibers exhibited a more pronounced effect on the properties of functional network.
Highlights
There are still uncertainties about the true nature of age related changes in topological properties of the brain functional network and its structural connectivity during various developmental stages
Functional studies have investigated the effects of age on functional brain connectivity showing older adults to have lower functional connectivity between regions of the default mode network compared to younger adults (Ferreira and Busatto, 2013; Dennis and Thompson, 2014)
Recent advances in network analysis have provided new insights into both structural and functional connectivity pattern, which is considered as the core of the brain activity (Sporns et al, 2005; Bullmore and Bassett, 2011; Sporns, 2012), it is still not fully understood about the relationships between them across lifespan, the evaluation of which might help us elucidate the possible mechanisms behind age related neurodegenerative diseases
Summary
There are still uncertainties about the true nature of age related changes in topological properties of the brain functional network and its structural connectivity during various developmental stages. Aging is considered as one of the greatest risk factors for neurodegenerative diseases where there is progressive loss of either structure or function of the neurons (Morrison and Hof, 1997) It is well-stipulated that marked transformations in white matter structure occur as early as third trimester (Ball et al, 2014) which persists throughout childhood and adolescence (Lebel et al, 2008; Hagmann et al, 2010; Tamnes et al, 2010; Dubois et al, 2014; van den Heuvel et al, 2015; Wierenga et al, 2016). Recent advances in network analysis have provided new insights into both structural and functional connectivity pattern, which is considered as the core of the brain activity (Sporns et al, 2005; Bullmore and Bassett, 2011; Sporns, 2012), it is still not fully understood about the relationships between them across lifespan, the evaluation of which might help us elucidate the possible mechanisms behind age related neurodegenerative diseases
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