Department of Neurology, University of Pennsylvania, Philadelphia PA, USA ; Penn Memory Center, University of Pennsylvania, Philadelphia PA, USA.
Department of Neurology, University of Pennsylvania, Philadelphia PA, USA ; Penn Memory Center, University of Pennsylvania, Philadelphia PA, USA ; Department of Psychiatry, University of Pennsylvania, Philadelphia PA, USA.
Front Aging Neurosci. 2013 Dec 11;5:89. doi: 10.3389/fnagi.2013.00089. eCollection 2013.
Episodic memory loss is the hallmark cognitive dysfunction associated with Alzheimer's disease (AD). Amnestic mild cognitive impairment (a-MCI) frequently represents a transitional stage between normal aging and early AD. A better understanding of the qualitative features of memory loss in a-MCI may have important implications for predicting those most likely to harbor AD-related pathology and for disease monitoring. Dual process models of memory argue that recognition memory is subserved by the dissociable processes of recollection and familiarity. Work studying recognition memory in a-MCI from this perspective has been controversial, particularly with regard to the integrity of familiarity. Event-related potentials (ERPs) offer an alternative means for assessing these functions without the associated assumptions of behavioral estimation methods. ERPs were recorded while a-MCI patients and cognitively normal (CN) age-matched adults performed a recognition memory task. When retrieval success was measured (hits versus correct rejections) in which performance was matched by group, a-MCI patients displayed similar neural correlates to that of the CN group, including modulation of the FN400 and the late positive complex (LPC) which are thought to index familiarity and recollection, respectively. Alternatively, when the integrity of these components was measured based on retrieval attempts (studied versus unstudied items), a-MCI patients displayed a reduced FN400 and LPC. Furthermore, modulation of the FN400 correlated with a behavioral estimate of familiarity and the LPC with a behavioral estimate of recollection obtained in a separate experiment in the same individuals, consistent with the proposed mappings of these indices. These results support a global decline of recognition memory in a-MCI, which suggests that the memory loss of prodromal AD may be qualitatively distinct from normal aging.
情景记忆丧失是与阿尔茨海默病（AD）相关的认知功能障碍的标志。遗忘型轻度认知障碍（a-MCI）通常代表正常衰老和早期 AD 之间的过渡阶段。更好地了解 a-MCI 中记忆丧失的定性特征可能对预测那些最有可能存在 AD 相关病理学以及疾病监测具有重要意义。记忆的双加工模型认为，识别记忆由可分离的再认和熟悉过程来支持。从这个角度研究 a-MCI 中的识别记忆的工作一直存在争议，特别是在熟悉的完整性方面。事件相关电位（ERP）提供了一种替代方法来评估这些功能，而无需行为估计方法的相关假设。当 a-MCI 患者和认知正常（CN）年龄匹配的成年人执行识别记忆任务时，记录了 ERP。当以匹配组内表现的方式测量检索成功（命中与正确拒绝）时，a-MCI 患者表现出与 CN 组相似的神经相关性，包括 FN400 和晚期正成分（LPC）的调制，分别被认为是熟悉度和再认的指标。相反，当根据检索尝试（已学习与未学习项目）测量这些成分的完整性时，a-MCI 患者显示 FN400 和 LPC 减少。此外，FN400 的调制与在同一组个体中进行的单独实验中获得的行为熟悉度估计相关，而 LPC 与行为再认估计相关，与这些指数的提出的映射一致。这些结果支持 a-MCI 中识别记忆的整体下降，这表明前驱 AD 的记忆丧失可能在质量上与正常衰老不同。
