Abstract
.A good understanding of age-dependent changes and modifications in brain networks is crucial for fully exploring the effects of aging on the human brain. Few reports have been found in studies of functional brain networks using functional near-infrared spectroscopy (fNIRS). Moreover, little is known about the feasibility of using fNIRS to assess age-related changes in brain connectomes. This study applied whole brain fNIRS measurement, combined with graph theory analysis, to assess the age-dependent changes in resting-state brain networks. Five to eight minutes of resting-state brain hemodynamic signals were recorded from 48 participants (18 young adults and 30 older adults) with 133 optical channels covering the majority of the cortical regions. Both local and global graph metrics were computed to identify the age-related changes of topographical brain networks. Older adults showed an overall decline of both global and local efficiency compared to young adults, as well as the decline of small-worldness. In addition, young adults showed the abundance of hubs in the prefrontal cortex, whereas older adults revealed the hub shifts to the sensorimotor cortex. These obvious shifts of hubs may potentially indicate decreases of the decision-making, memory, and other high-order functions as people age. Our results showed consistent findings with published literature and also demonstrated the feasibility of whole-head fNIRS measurements to assess age-dependent changes in resting-state brain networks.
Highlights
The human brain is organized in a set of networks, with anatomical brain regions involved in either individualized processing or integration with other brain regions, to accomplish different functions.[1,2] Both anatomical and functional brain networks change in their properties as normal aging commences in humans
There was no significant difference between two groups when S > 0.3
The functional near-infrared spectroscopy (fNIRS) measurements taken from the scalp surface gather a majority of the information from the gray matter in the cortical regions; this study reveals global and local graphical metrics for only cortical connectivity and networks
Summary
The human brain is organized in a set of networks, with anatomical brain regions involved in either individualized processing or integration with other brain regions, to accomplish different functions.[1,2] Both anatomical and functional brain networks change in their properties as normal aging commences in humans. Some research studies have shown that the decline of gray matter in older individuals is most responsible for agerelated changes in brain anatomy.[1,3] Early studies have reported the preservation of small-world and economic brain characteristics in older adults,[1] with a decrease of efficiency mostly in frontal and temporal cortical and subcortical regions.[4] These findings explain well that, as people age, there is a decrease in their cognitive abilities, such as memory, attention, and concentration, which are functions controlled by the prefrontal cortex in humans. Understanding age-related alterations in human brain networks can help better understand the cognitive declines, guide early diagnosis of geriatric diseases, such as Alzheimer’s disease,[8] Parkinson’s disease,[9] and other dementias in older patients, and provide insight into effective treatments for these illnesses
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