Spreng R Nathan, Stevens W Dale, Viviano Joseph D, Schacter Daniel L
Laboratory of Brain and Cognition, Department of Human Development, Cornell University, Ithaca, NY, USA; Human Neuroscience Institute, Cornell University, Ithaca, NY, USA.
Cognition and Aging Neuroscience Laboratory, Department of Psychology, York University, Toronto, Ontario, Canada.
Neurobiol Aging. 2016 Sep;45:149-160. doi: 10.1016/j.neurobiolaging.2016.05.020. Epub 2016 Jun 3.
Anticorrelation between the default and dorsal attention networks is a central feature of human functional brain organization. Hallmarks of aging include impaired default network modulation and declining medial temporal lobe (MTL) function. However, it remains unclear if this anticorrelation is preserved into older adulthood during task performance, or how this is related to the intrinsic architecture of the brain. We hypothesized that older adults would show reduced within- and increased between-network functional connectivity (FC) across the default and dorsal attention networks. To test this hypothesis, we examined the effects of aging on task-related and intrinsic FC using functional magnetic resonance imaging during an autobiographical planning task known to engage the default network and during rest, respectively, with young (n = 72) and older (n = 79) participants. The task-related FC analysis revealed reduced anticorrelation with aging. At rest, there was a robust double dissociation, with older adults showing a pattern of reduced within-network FC, but increased between-network FC, across both networks, relative to young adults. Moreover, older adults showed reduced intrinsic resting-state FC of the MTL with both networks suggesting a fractionation of the MTL memory system in healthy aging. These findings demonstrate age-related dedifferentiation among these competitive large-scale networks during both task and rest, consistent with the idea that age-related changes are associated with a breakdown in the intrinsic functional architecture within and among large-scale brain networks.
默认网络与背侧注意网络之间的反相关是人类功能性脑组织结构的一个核心特征。衰老的标志包括默认网络调节受损和内侧颞叶（MTL）功能下降。然而，目前尚不清楚这种反相关在任务执行过程中是否会保留到老年期，或者它与大脑的内在结构有何关系。我们假设老年人在默认网络和背侧注意网络中会表现出网络内功能连接性（FC）降低以及网络间功能连接性增加。为了验证这一假设，我们分别在一项已知会激活默认网络的自传体计划任务期间以及休息时，使用功能磁共振成像检查了衰老对任务相关和内在FC的影响，参与者包括年轻人（n = 72）和老年人（n = 79）。任务相关的FC分析显示，随着年龄增长，反相关降低。在休息时，存在一种强烈的双重分离现象，相对于年轻人，老年人在两个网络中均表现出网络内FC降低但网络间FC增加的模式。此外，老年人与两个网络的MTL内在静息态FC均降低，这表明在健康衰老过程中MTL记忆系统发生了分化。这些发现表明，在任务和休息期间，这些竞争性大规模网络之间存在与年龄相关的去分化，这与年龄相关变化与大规模脑网络内部和之间的内在功能结构破坏相关的观点一致。
