White-matter connectivity and the reorganization of brain networks in aging

描述（由申请人提供）：许多功能性磁共振成像（fMRI）研究表明，老年人通常表现出与年轻人成功完成任务相关的皮质网络之外的激活增加。许多研究表明，表现出色的老年人表现出在年轻人或表现不佳的同龄人中没有观察到的双侧大脑活动模式，以及将处理从后部感觉区域转移到前部联合区域的总体趋势。这些模式的模型，老年人的半球不对称减少（HAROLD），以及对侧和前部募集（分别为CR和AR）增加的老化中的后移到前移（PASA），作为与正常老化相关的生物降解所带来的资源需求增加的补偿机制。为了进一步了解衰老过程中大脑网络重组的变化，我们试图确定CR和AR的神经相关性。我们将首先试图表明，老年人受益于双边比单边处理（双边领域优势：BFA）在分裂视野范例（具体目标1）。我们将使用扩散张量成像（DTI）来评估介导BFA的连接的结构形态（特定目标2），以及白色物质完整性对支持BFA的激活功能网络的影响（特定目标3）。因此，我们提出了一系列的多模态实验，依赖于侧匹配的任务，旨在操纵内和对侧和同侧大脑区域之间的半球内的通信需求。我们预计激活与成功的表现在老年人观察到更多的正面和双边模式相对于年轻的成年人，更大的纤维完整性将介导认知性能的增加，支持老化的补偿帐户。拟议的研究计划提供了几种新的方法来研究有效大脑网络的年龄相关重组，并将阐明白质连接在支持健康老龄化中的作用。此外，该项目旨在描述有助于抵消衰老不利影响的机制，并建议在健康和病理性老龄化人群中进行认知疗法。

DESCRIPTION (provided by applicant): A number of functional magnetic resonance imaging (fMRI) studies have show that older individuals often show increased activation outside of the cortical networks typically associated with successful task performance in young adults. Many of these studies have shown that high-performing older adults show both a bilateral pattern of brain activity not observed in young adults or in their low-performing counterparts, as well as a general trend to shift processing from posterior sensory regions to anterior association regions. The models of these patterns, the Hemispheric Asymmetry Reduction in Older adults (HAROLD), and the Posterior to Anterior Shift in Aging (PASA) posit that increases in contralateral and anterior recruitment (CR and AR, respectively) act as compensatory mechanisms for the increase in resource demands brought about by the biological degradation associated with normal aging. To further the understanding of changes in the reorganization of brain networks in aging we seek to identify the neural correlates of CR and AR. We will first seek to show that older adults benefit from bilateral more than unilateral processing (bilateral field advantage: BFA) in a split-visual field paradigm (Specific Aim 1). We will use diffusion tensor imaging (DTI) to evaluate both the structural morphology of the connection that mediate BFA (Specific Aim 2), as well as the influence of white matter integrity on functional networks of activation supporting BFA (Specific Aim 3). We therefore propose a series of multimodal experiments that rely on lateralized matching tasks designed to manipulate intra- and intrahemispheric communication demands between contralateral and ipsilateral brain regions. We expect activations associated with successful performance in older adults to observe a more frontal and bilateral pattern relative to young adult subjects, and that greater fiber integrity will mediate increases in cognitive performance, supporting compensatory accounts of aging. The proposed research program offers several novel approaches to the study of age-related reorganization of effective brain networks, and will clarify the role of white-matter connectivity in supporting healthy aging. Furthermore, this project seeks to characterize mechanisms that help to offset the detrimental effects of aging, and suggests cognitive therapies in both healthy and pathological aging populations.