根据一项新的研究，年轻人最喜欢欣喜地期待着打开礼物，该研究揭示出了我们对奖赏的反应随着衰老而变得成熟的生物化学原因。Karen Faith Berman及其同事联合使用了几种大脑成像技术从而寻找当更年轻和更年长的成年人得到奖赏——或得到奖赏的承诺——的时候，大脑的哪些部分受到了刺激。多巴胺被认为是大脑的奖赏处理回路的货币，而且尽管大脑的多巴胺系统作为正常衰老的一部分而自然衰退，这种衰退的后果仍然令人难以捉摸。
这组科学家利用功能磁共振成像（fMRI）扫描证明了，在视频投币游戏机上预料到或者获得一个奖赏的时候，平均年龄25岁的年轻受试者比平均年龄65岁的老年受试者的多巴胺触发的大脑区域的激活更加显著。尽管正电子发射计算机断层扫描（PET）显示年轻和年长的受试者大脑多巴胺的生产没有差异，这组作者发现了在人类的多巴胺合成（用PET测量）和奖赏相关的大脑活动（用fMRI测量）之间的联系，发现了大脑调节回路伴随着正常衰老的一些变化。相关论文发表在美国《国家科学院院刊》（PNAS）上。（生物谷Bioon.com）
生物谷推荐原始出处：
PNAS，doi: 10.1073/pnas.0802127105，Jean-Claude Dreher，Karen Faith Berman
Age-related changes in midbrain dopaminergic regulation of the human reward system
Jean-Claude Dreher, Andreas Meyer-Lindenberg, Philip Kohn, and Karen Faith Berman
The dopamine system, which plays a crucial role in reward processing, is particularly vulnerable to aging. Significant losses over a normal lifespan have been reported for dopamine receptors and transporters, but very little is known about the neurofunctional consequences of this age-related dopaminergic decline. In animals, a substantial body of data indicates that dopamine activity in the midbrain is tightly associated with reward processing. In humans, although indirect evidence from pharmacological and clinical studies also supports such an association, there has been no direct demonstration of a link between midbrain dopamine and reward-related neural response. Moreover, there are no in vivo data for alterations in this relationship in older humans. Here, by using 6-[18F]FluoroDOPA (FDOPA) positron emission tomography (PET) and event-related 3T functional magnetic resonance imaging (fMRI) in the same subjects, we directly demonstrate a link between midbrain dopamine synthesis and reward-related prefrontal activity in humans, show that healthy aging induces functional alterations in the reward system, and identify an age-related change in the direction of the relationship (from a positive to a negative correlation) between midbrain dopamine synthesis and prefrontal activity. These results indicate an age-dependent dopaminergic tuning mechanism for cortical reward processing and provide system-level information about alteration of a key neural circuit in healthy aging. Taken together, our findings provide an important characterization of the interactions between midbrain dopamine function and the reward system in healthy young humans and older subjects, and identify the changes in this regulatory circuit that accompany aging.
