Alteration of the Intra- and Inter-Lobe Connectivity of the Brain Structural Network in Normal Aging

Abstract

The morphological changes in cortical parcellated regions during aging and whether these atrophies may cause brain structural network intra- and inter-lobe connectivity alterations are subjects that have been minimally explored. In this study, a novel fractal dimension-based structural network was proposed to measure atrophy of 68 parcellated cortical regions. Alterations of structural network parameters, including intra- and inter-lobe connectivity, were detected in a middle-aged group (30–45 years old) and an elderly group (50–65 years old). The elderly group exhibited significant lateralized atrophy in the left hemisphere, and most of these fractal dimension atrophied regions were included in the regions of the “last-in, first-out” model. Globally, the elderly group had lower modularity values, smaller component size modules, and fewer bilateral association fibers. They had lower intra-lobe connectivity in the frontal and parietal lobes, but higher intra-lobe connectivity in the temporal and occipital lobes. Both groups exhibited similar inter-lobe connecting pattern. The elderly group revealed separations, sparser long association fibers, commissural fibers, and lateral inter-lobe connectivity lost effect, mainly in the right hemisphere. New wiring and reconfiguring modules may have occurred within the brain structural network to compensate for connectivity, decreasing and preventing functional loss in cerebral intra- and inter-lobe connectivity.

Age‐Related Differences of Cortical Topology Across the Adult Lifespan: Evidence From a Multisite MRI Study With 1427 Individuals

“…The propensity may be that the age‐associated decline of structural modular architecture of the human cortical brain is hemispherically asymmetric: middle‐aged individuals generally have higher co‐coordination of nodes within the left hemisphere and lower co‐coordination of nodes within the right hemisphere compared with young and elderly adults. Previous research has found significantly lateralized atrophy of the left hemisphere in the elderly, which may relevant to the downward trend of intramodular connectivity within the left hemisphere since middle‐age 39 . The higher co‐coordination within the right hemisphere since middle‐age seems to be the compensation for the connectivity decrease and functional loss 39 …”

“…Previous research has found significantly lateralized atrophy of the left hemisphere in the elderly, which may relevant to the downward trend of intramodular connectivity within the left hemisphere since middle-age. 39 The higher co-coordination within the right hemisphere since middle-age seems to be the compensation for the connectivity decrease and functional loss. 39…”

“…39 The higher co-coordination within the right hemisphere since middle-age seems to be the compensation for the connectivity decrease and functional loss. 39…”

How the Brain Becomes the Mind: Can Thermodynamics Explain the Emergence and Nature of Emotions?

“…One may conceive that hemispheric asymmetry could result in uneven thermodynamics between the brain hemispheres [ 136 ] but the structural analysis of intra- and inter-lobe connectivity is beyond the present work.…”

Entropy in Brain Networks

“…In this regard, the combination of measures from information theory with both structural and functional connectivity analyses yields a new framework to further understand brain organization. This can be observed in the work of Jao et al [ 10 ], in which irregularity of the network anatomical structure, in particular inter- and intra-lobe brain connectivity, was analyzed using the fractal dimension. Their results suggested that aging induces morphological changes in the structural brain network generated from magnetic resonance imaging (MRI), which could be related to rewiring and reconfiguring modules as compensatory mechanisms for the functional deficit in inter- and intra-lobe brain connectivity.…”