Department of Psychology, Durham University, Durham, UK.
Int J Neurosci. 2011 Jul;121(7):384-92. doi: 10.3109/00207454.2011.565892. Epub 2011 Mar 29.
The aim of our study was to examine brain networks involved with sustaining memory encoding performance in healthy aging and in Alzheimer's disease (AD). Since different brain regions are affected by degradation in these two conditions, it might be conceivable that different compensation mechanisms occur to keep up memory performance in aging and in AD. Using an event-related functional magnetic resonance imaging (FMRI) design and a correlation analysis, 8 patients suffering from AD and 29 elderly control subjects were scanned while they studied a list of words for a subsequent memory test. Individual performance was assessed on the basis of a subsequent recognition test, and brain regions were identified where functional activations during study correlated with memory performance. In both groups, successful memory encoding performance was significantly correlated with the activation of the right frontal cortex. Furthermore, in healthy controls, there was a significant correlation of memory performance and the activation of the left medial and lateral temporal lobe. In contrast, in AD patients, increasing memory performance goes along with increasing activation of the hippocampus and a bilateral brain network including the frontal and temporal cortices. Our data show that in healthy aging and in AD, common and distinct compensatory mechanisms are employed to keep up a certain level of memory performance. Both in healthy aging and in patients with AD, an increased level of monitoring and control processes mediated by the (right) frontal lobe seems to be necessary to maintain a certain level of memory performance. In addition, memory performance in healthy older subjects seems to rely on an increased effort in encoding item-specific semantic and contextual information in lateral areas of the (left) temporal lobe. In AD patients, on the other hand, the maintenance of memory performance is related to an increase of activation of the (left) hippocampus in conjunction with a bilateral network of cortical areas that might be involved with phonological and visual rehearsal of the incoming information.
我们的研究目的是检验在健康老化和阿尔茨海默病（AD）中与维持记忆编码表现相关的大脑网络。由于在这两种情况下，不同的大脑区域受到退化的影响，因此可以想象，在老化和 AD 中会发生不同的补偿机制来保持记忆表现。我们使用事件相关功能磁共振成像（fMRI）设计和相关分析，对 8 名 AD 患者和 29 名老年对照组进行了扫描，这些患者在进行后续记忆测试时学习了一系列单词。根据后续识别测试评估个体表现，并确定在研究过程中与记忆表现相关的功能激活的大脑区域。在两组中，成功的记忆编码表现与右侧额叶的激活显著相关。此外，在健康对照组中，记忆表现与左侧内侧和外侧颞叶的激活存在显著相关性。相比之下，在 AD 患者中，记忆表现的提高伴随着海马体和包括额叶和颞叶在内的双侧大脑网络的激活增加。我们的数据表明，在健康老化和 AD 中，使用了共同和独特的补偿机制来保持一定的记忆表现水平。在健康老化和 AD 患者中，由（右）额叶介导的监测和控制过程的增加水平似乎是维持一定记忆表现水平所必需的。此外，健康老年受试者的记忆表现似乎依赖于在（左）颞叶外侧区域增加对项目特异性语义和上下文信息的编码努力。另一方面，在 AD 患者中，记忆表现的维持与（左）海马体激活的增加有关，同时还涉及到皮质区域的双侧网络，这些区域可能与传入信息的语音和视觉复述有关。
