| The aging of the population is a huge challenge for today’s society.Normal aging is associated with cognitive decline,such as working memory,processing speed,and episodic memory,which have an impact on the independence and quality of life of older adults.The human brain is the physical basis for various cognitive functions.It is an important topic of cognitive aging to clarify functional and structural brain changes with aging.Accumulating cognitive neuroscience research has recast our framework around cognitive aging.On the one hand,cognitive decline is caused by structural and functional brain changes with aging;on the other hand,cognitive intervention that results in changes in brain function and structure can improve the cognitive function of the older adults.The current study is dedicated to explore changes of brain functional networks with aging and after cognitive intervention using functional magnetic resonance imaging(fMRI)technology.Healthy older adults were included as subjects.Main works and findings in this dissertation are introduced as follows:1.Effects of aging on brain function network of the anterior cingulate(ACC).The ACC,an important region of the frontal lobe,is associated with cognitive control and emotional reglualtion.Based on resting state fMRI data,we investigated differences of functional network of the ACC between older adults and younger controls.First,the ACC was parcellated into dorsal(dACC)and rostral(rACC)ACC based on clustering of functional connectivity profiles,and then the effects of aging on functional networks of dACC and rACC were explored.We found that older adults had a greater volume ratio of dACC to rACC related to younger adults,suggesting functional reorgnization within the ACC with aging.The further functional connectivity analysis revealed increased functional connectivity between dACC and temporoparietal junction and between rACC and anterior insula in older adults relative to younger adults,suggesting the effects of aging on the SN,in which older adults might need more resources to maintain salient responses.Older adults also demonstrated decreased integration between the rACC and default mode,as well as decreased dACC-hippocampal and-thalamic connectivity.These findings,decreased functional connections,might be associated with decline in cognitive function,such as working memory with aging.In addition,the rACC also showed increased connection with the superior temporal gyrus and inferior frontal gyrus in older adults,which underlie maintenance of emotional well-being in older adults.2.Effects of aging on the cerebellar networks.Based on resting state fMRI data,we found decreased functional connectivity between the cerebellum and the prefrontal cortex,hippocampus and the striatum in older adults relative to younger adults.Older adults showed increased functional connection with the insula,but decreased connection with the motor cortex.These findings indicated that these age differences of cerebellar networks have potential for understanding behavioral decline in both cognitive and sensorimotor function with aging.3.Effects of aging on function networks associated with working memory(WM).We investigated differences of three cognitive networks(central executive network(CEN),salience network(SN)and default mode network(DMN))between older and younger adults using task activation and functional connectivity analysis.Compared with younger adults,older adults showed lower accuracy and longer reaction time at higher WM load.We found significant decreased activation in left posterior parietal lobe and decreased deactivation in the DMN at higher WM load,suggesting that older adults might have no more cognitive resources to be allocated,and perform worse.The results of functional connectivity analysis demonstrated decreased functional connectivity within and between the three networks at higher WM load in older adults relative to younger adults.These findings showed that aging influenced the intra-network integration and inter-network coupling of three cognitive functional networks during WM task,maybe reflecting WM decline in older adults.4.Effects of cognitive interventions on cognitive networks associated with WM in older adults.We examined changes in functional connectivity within and between three cognitive networks(CEN,SN,and DMN)at baseline and at one year after intervention ended.Compared with the wait-list older adults,we found maintained functional integration of the DMN and SN and increased functional integration of the CEN in the intervention older adults at one year after intervention ended.Furthermore,there was a positive correlation between changes of functional connectivity within the CEN and SN and change of cognitive assessment scores in older adults.We also found maintained functional coupling between the DMN and CEN in the intervention group at one year after intervention ended.These findings might indicate that cognitive intervention delay age-related changes in cognitive networks,and thus enhance cognitive function,such as working memory in older adults.5.Effects of cognitive interventions on hippocampal functional networks in older adults.We provided a comprehensive exploration of hippocampal functional network in aging and after cognitive intervention.For the anterior hippocampal functional network,compared with younger adults,older adults showed decreased connection with the temporal pole and increased connection with the medial prefrontal cortex,suggesting the anterior hippocampal functional network reorganization in aging.After cognitive intervention,we found maintained functional connectivity between left anterior hippocampus and right temporal pole in the intervention older adults related to the waitlist older adults.For the posterior hippocampal functional network,we found significant decreased functional connectivity between hippocampus and cortex in older adults relative to younger adults,and cognitive intervention did not prevent or delay the effects of aging on the posterior hippocampal functional network.These findings of this study demonstrated that aging has an impact on hippocampal functional networks associated with cognitive decline,such as memory impairment in the older adults.However,cognitive intervention delay effects of aging on the anterior hippocampal functional network related to the posterior hippocampal functional network.In summary,we found that feature changes of brain functional networks associated with cognitive aging,such as working memory declines,whereas cognitive intervention could prevent or delay the effects of aging on brain functional networks.These results provide further insight into potential neural mechanism of cognitive aging,and important neuroimaging evidence for establishing cognitive interventions to delay the progression of aging and prevent Alzheimer’s disease. |
PDF Full Text Request