Center for Cognitive Neuroscience, Duke University, Durham, North Carolina 27708, USA.
J Neurosci. 2010 Feb 17;30(7):2490-5. doi: 10.1523/JNEUROSCI.3319-09.2010.
The core feature of an economic exchange is a decision to trade one good for another, based on a comparison of relative value. Economists have long recognized, however, that the value an individual ascribes to a good during decision making (i.e., their relative willingness to trade for that good) does not always map onto the reward they actually experience. Here, we show that experienced value and decision value are represented in distinct regions of ventromedial prefrontal cortex (VMPFC) during the passive consumption of rewards. Participants viewed two categories of rewards-images of faces that varied in their attractiveness and monetary gains and losses-while being scanned using functional magnetic resonance imaging. An independent market task, in which participants exchanged some of the money that they had earned for brief views of attractive faces, determined the relative decision value associated with each category. We found that activation of anterior VMPFC increased with increasing experienced value, but not decision value, for both reward categories. In contrast, activation of posterior VMPFC predicted each individual's relative decision value for face and monetary stimuli. These results indicate not only that experienced value and decision value are represented in distinct regions of VMPFC, but also that decision value signals are evident even in the absence of an overt choice task. We conclude that decisions are made by comparing neural representations of the value of different goods encoded in posterior VMPFC in a common, relative currency.
经济交换的核心特征是基于相对价值比较，做出用一种商品换取另一种商品的决策。然而，经济学家早就认识到，个体在决策过程中赋予商品的价值（即他们相对愿意用该商品进行交换的程度）并不总是与其实际获得的奖励相匹配。在这里，我们表明，在奖励的被动消费过程中，体验价值和决策价值在腹内侧前额叶皮层（VMPFC）的不同区域得到体现。参与者在接受功能磁共振成像扫描的同时，观看了两类奖励——吸引力不同的人脸图像和金钱的得失——的图片。在一个独立的市场任务中，参与者用他们挣到的一部分钱换取短暂观看有吸引力的人脸，从而确定与每个类别相关的相对决策价值。我们发现，对于两种奖励类别，VMPFC 的前区激活程度随着体验价值的增加而增加，但不随决策价值的增加而增加。相比之下，VMPFC 的后区激活程度预测了个体对人脸和金钱刺激的相对决策价值。这些结果不仅表明体验价值和决策价值在 VMPFC 的不同区域得到体现，而且表明即使在没有明显选择任务的情况下，决策价值信号也是明显的。我们的结论是，决策是通过比较后 VMPFC 中不同商品价值的神经表示，以一种共同的相对货币进行的。
