Aging Research Center, Karolinska Institutet, Gävlegatan 16, SE-113 30 Stockholm, Sweden.
Neurobiol Aging. 2011 Oct;32(10):1849-56. doi: 10.1016/j.neurobiolaging.2009.10.018. Epub 2009 Dec 4.
In an fMRI study, 20 younger and 20 healthy older adults were scanned while performing a spatial working-memory task under two levels of load. On a separate occasion, the same subjects underwent PET measurements using the radioligand [(11)C] SCH23390 to determine dopamine D(1) receptor binding potential (BP) in caudate nucleus and dorsolateral prefrontal cortex (DLPFC). The fMRI study revealed a significant load modulation of brain activity (higher load>lower load) in frontal and parietal regions for younger, but not older, adults. The PET measurements showed marked age-related reductions of D(1) BP in caudate and DLPFC. Statistical control of caudate and DLPFC D(1) binding eliminated the age-related reduction in load-dependent BOLD signal in left frontal cortex, and attenuated greatly the reduction in right frontal and left parietal cortex. These findings suggest that age-related alterations in dopaminergic neurotransmission may contribute to underrecruitment of task-relevant brain regions during working-memory performance in old age.
在一项 fMRI 研究中，20 名年轻成年人和 20 名健康老年人在执行空间工作记忆任务时，分别在两个负荷水平下接受扫描。在另一个场合，相同的受试者接受了使用放射性配体 [(11)C]SCH23390 的 PET 测量，以确定尾状核和背外侧前额叶皮层 (DLPFC) 中的多巴胺 D1 受体结合潜能 (BP)。该 fMRI 研究表明，年轻成年人的额叶和顶叶区域的大脑活动存在显著的负荷调制（高负荷>低负荷），但老年人没有。PET 测量显示，尾状核和 DLPFC 中的 D1BP 随年龄相关显著减少。对尾状核和 DLPFC 的 D1 结合进行统计学控制，消除了左额皮质中与年龄相关的与负荷相关的 BOLD 信号减少，并且大大减弱了右额皮质和左顶叶皮质的减少。这些发现表明，多巴胺能神经传递的年龄相关改变可能导致老年人在工作记忆表现期间任务相关脑区的招募不足。
