Max Planck Institute for Human Development, Center for Lifespan Psychology, Lentzealle 94, 14195 Berlin, Germany; Humboldt-Universität zu Berlin, Department of Psychology, Unter den Linden 6, 10099 Berlin, Germany.
Neuropsychologia. 2013 Nov;51(13):2757-69. doi: 10.1016/j.neuropsychologia.2013.09.009. Epub 2013 Sep 12.
The striatum and medial temporal lobe play important roles in implicit and explicit memory, respectively. Furthermore, recent studies have linked striatal dopamine modulation to both implicit as well as explicit sequence learning and suggested a potential role of the striatum in the emergence of explicit memory during sequence learning. With respect to aging, previous findings indicated that implicit memory is less impaired than explicit memory in older adults and that genetic effects on cognition are magnified by aging. To understand the links between these findings, we investigated effects of aging and genotypes relevant for striatal dopamine on the implicit and explicit components of sequence learning. Reaction time (RT) and error data from 80 younger (20-30 years) and 70 older adults (60-71 years) during a serial reaction time task showed that age differences in learning-related reduction of RTs emerged gradually over the course of learning. Verbal recall and measures derived from the process-dissociation procedure revealed that younger adults acquired more explicit memory about the sequence than older adults, potentially causing age differences in RT gains in later stages of learning. Of specific interest, polymorphisms of the dopamine- and cAMP-regulated neuronal phosphoprotein (DARPP-32, rs907094) and dopamine transporter (DAT, VNTR) genes showed interactive effects on overall RTs and verbal recall of the sequence in older but not in younger adults. Together our findings show that variations in genotypes relevant for dopamine functions are associated more with aging-related impairments in the explicit than the implicit component of sequence learning, providing support for theories emphasizing the role of dopaminergic modulation in cognitive aging and the magnification of genetic effects in human aging.
纹状体和内侧颞叶分别在内隐记忆和外显记忆中起重要作用。此外，最近的研究将纹状体多巴胺调节与内隐和外显序列学习联系起来，并表明纹状体在序列学习过程中外显记忆的出现中可能发挥作用。关于衰老，先前的研究表明，老年人的内隐记忆比外显记忆受损程度较小，并且认知的遗传效应会随着年龄的增长而放大。为了理解这些发现之间的联系，我们研究了与纹状体多巴胺相关的衰老和基因型对外显和内隐序列学习成分的影响。80 名年轻成年人（20-30 岁）和 70 名老年成年人（60-71 岁）在序列反应时间任务中的反应时间（RT）和错误数据表明，学习相关 RT 降低的年龄差异随着学习过程的进行而逐渐出现。口头回忆和来自过程分离程序的测量结果表明，年轻成年人比老年成年人获得了更多关于序列的外显记忆，这可能导致学习后期 RT 增益的年龄差异。特别值得注意的是，多巴胺和 cAMP 调节的神经元磷酸蛋白（DARPP-32，rs907094）和多巴胺转运蛋白（DAT，VNTR）基因的多态性对老年人的整体 RT 和序列的口头回忆表现出交互作用，但对年轻人没有影响。我们的研究结果表明，与多巴胺功能相关的基因型的变化与序列学习的外显成分而不是内隐成分的与衰老相关的损伤更为相关，这为强调多巴胺调节在认知衰老中的作用以及遗传效应在人类衰老中放大的理论提供了支持。
