Athinoula A. Martinos Center for Biomedical Imaging, Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA.
Neurobiol Aging. 2012 Jul;33(7):1237-52. doi: 10.1016/j.neurobiolaging.2011.01.003. Epub 2011 Feb 18.
The neural networks supporting encoding of new information are thought to decline with age, although mnemonic techniques such as repetition may enhance performance in older individuals. Accumulation of amyloid-β, one hallmark pathology of Alzheimer's disease (AD), may contribute to functional alterations in memory networks measured with functional magnetic resonance imaging (fMRI) prior to onset of cognitive impairment. We investigated the effects of age and amyloid burden on fMRI activity in the default network and hippocampus during repetitive encoding. Older individuals, particularly those with high amyloid burden, demonstrated decreased task-induced deactivation in the posteromedial cortices during initial stimulus presentation and failed to modulate fMRI activity in response to repeated trials, whereas young subjects demonstrated a stepwise decrease in deactivation with repetition. The hippocampus demonstrated similar patterns across the groups, showing task-induced activity that decreased in response to repetition. These findings demonstrate that age and amyloid have dissociable functional effects on specific nodes within a distributed memory network, and suggest that functional brain changes may begin far in advance of symptomatic Alzheimer's disease.
据认为，支持新信息编码的神经网络会随着年龄的增长而衰退，尽管重复等记忆技巧可能会提高老年人的表现。淀粉样蛋白-β的积累是阿尔茨海默病 (AD) 的一个标志性病理学特征，它可能导致在认知障碍出现之前，通过功能磁共振成像 (fMRI) 测量的记忆网络的功能改变。我们研究了年龄和淀粉样蛋白负担对重复编码期间默认网络和海马体 fMRI 活动的影响。老年人，尤其是淀粉样蛋白负担较高的老年人，在初始刺激呈现期间在后扣带回皮质中表现出任务诱发去激活的减少，并且无法响应重复试验来调节 fMRI 活动，而年轻受试者则随着重复的进行逐渐减少去激活。海马体在各个组中表现出相似的模式，显示出随着重复而减少的任务诱发活动。这些发现表明，年龄和淀粉样蛋白对分布式记忆网络中的特定节点具有可分离的功能影响，并表明功能性脑变化可能早在有症状的阿尔茨海默病之前就开始了。
