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

描述(申请人提供)：许多功能磁共振成像(FMRI)研究表明，老年人通常表现出皮质网络外的激活增加，这通常与年轻人的成功任务表现有关。其中许多研究表明，表现良好的老年人既表现出年轻人或表现不佳的老年人没有观察到的双侧大脑活动模式，也表现出将加工从后感觉区域转移到前联合区域的总体趋势。这些模式的模型，老年人大脑半球不对称性的减少(Harold)，以及老龄化中的后移到前移(PASA)假设对侧和前部招募的增加(分别为CR和AR)作为正常衰老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脑网络重组的变化，我们试图确定CR和AR的神经关联。我们将首先试图证明，在分裂视野范式(具体目标1)中，老年人从双侧加工中受益多于单侧加工(双边视野优势：BFA)。我们将使用弥散张量成像(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，我们提出了一系列多模式实验，这些实验依赖于侧化匹配任务，旨在操纵对侧和同侧大脑区域之间的大脑半球内和大脑内通信需求。我们预计，与老年人的成功表现相关的激活与年轻人的受试者相比，会观察到更多的正面和双边模式，更好的纤维完整性将中介认知能力的提高，支持对衰老的补偿性解释。拟议的研究计划为研究与年龄相关的有效脑网络重组提供了几种新的方法，并将阐明白质连接在支持健康老龄化方面的作用。此外，该项目试图描述有助于抵消老龄化有害影响的机制，并建议在健康和病理性老龄化人群中进行认知治疗。

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.