Daselaar Sander M, Veltman Dick J, Rombouts Serge A R B, Raaijmakers Jeroen G W, Jonker Cees
Center for Cognitive Neuroscience, Duke University, Box 90999, LSRC Bldg., Rm B243N, Durham, NC 27708, USA.
Neurobiol Aging. 2003 Nov;24(7):1005-11. doi: 10.1016/s0197-4580(03)00032-0.
Age-related impairments in episodic memory have been related to a deficiency in semantic processing, based on the finding that elderly adults typically benefit less than young adults from deep, semantic as opposed to shallow, nonsemantic processing of study items. In the present study, we tested the hypothesis that elderly adults are not able to perform certain cognitive operations under deep processing conditions. We further hypothesised that this inability does not involve regions commonly associated with lexical/semantic retrieval processes, but rather involves a dysfunction of the medial temporal lobe (MTL) memory system. To this end, we used functional MRI on rather extensive groups of young and elderly adults to compare brain activity patterns obtained during a deep (living/nonliving) and a shallow (uppercase/lowercase) classification task. Common activity in relation to semantic classification was observed in regions that have been previously related to semantic retrieval, including mainly left-lateralised activity in the inferior prefrontal, middle temporal, and middle frontal/anterior cingulate gyrus. Although the young adults showed more activity in some of these areas, the finding of mainly overlapping activation patterns during semantic classification supports the idea that lexical/semantic retrieval processes are still intact in elderly adults. This received further support by the finding that both groups showed similar behavioural performances as well on the deep and shallow classification tasks. Importantly, though, the young revealed significantly more activity than the elderly adults in the left anterior hippocampus during deep relative to shallow classification. This finding is in line with the idea that age-related impairments in episodic encoding are, at least partly, due to an under-recruitment of the medial temporal lobe memory system.
情景记忆中与年龄相关的损伤与语义加工缺陷有关，这是基于以下发现：与年轻人相比，老年人通常从对学习项目的深度语义加工而非浅层次的非语义加工中获益更少。在本研究中，我们检验了这样一个假设，即老年人在深度加工条件下无法执行某些认知操作。我们进一步假设，这种无能并不涉及通常与词汇/语义检索过程相关的区域，而是涉及内侧颞叶（MTL）记忆系统的功能障碍。为此，我们对相当多的年轻和老年人群体进行了功能性磁共振成像，以比较在深度（有生命/无生命）和浅层次（大写/小写）分类任务期间获得的大脑活动模式。在先前与语义检索相关的区域观察到了与语义分类相关的共同活动，主要包括左下前额叶、颞中回以及额中回/前扣带回的左侧化活动。尽管年轻人在其中一些区域表现出更多的活动，但语义分类期间主要重叠的激活模式这一发现支持了这样一种观点，即老年人的词汇/语义检索过程仍然完好无损。两组在深度和浅层次分类任务上表现出相似的行为表现，这一发现进一步支持了上述观点。然而，重要的是，在深度分类相对于浅层次分类过程中，年轻人左侧前海马体的活动明显比老年人更多。这一发现与以下观点一致，即情景编码中与年龄相关的损伤至少部分是由于内侧颞叶记忆系统的招募不足。
