Miura Naoki, Tanabe Hiroki C, Sasaki Akihiro T, Harada Tokiko, Sadato Norihiro
Department of Information and Communication Engineering, Faculty of Engineering, Tohoku Institute of Technology, 35-1 Yagiyama Kasumicho, Taihaku-ku, Sendai, Miyagi 982-8577, Japan.
Division of Psychology, Department of Social and Human Environment, Graduate School of Environmental Studies, Nagoya University, D2-1(510), Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan.
Neuroscience. 2017 Jun 3;352:190-203. doi: 10.1016/j.neuroscience.2017.03.064. Epub 2017 Apr 8.
The intrinsic value of an action refers to the inherent sense that experiencing a behavior is enjoyable even if it has no explicit outcome. Previous research has suggested that a common valuation mechanism within the reward network may be responsible for processing the intrinsic value of achieving both the outcome and external rewards. However, how the intrinsic value of action is neurally represented remains unknown. We hypothesized that the intrinsic value of action is determined by an action-outcome contingency indicating the behavior is controllable and that the outcome of the action can be evaluated by this feedback. Consequently, the reward network should be activated, reflecting the generation of the intrinsic value of action. To test this hypothesis, we conducted a functional magnetic resonance imaging (fMRI) investigation of a stopwatch game in which the action-outcome contingency was manipulated. This experiment involved 36 healthy volunteers and four versions of a stopwatch game that manipulated controllability (the feeling that participants were controlling the stopwatch themselves) and outcome (a signal allowing participants to see the result of their action). A free-choice experiment was administered after the fMRI to explore preference levels for each game. The results showed that the stopwatch game with the action-outcome contingency evoked a greater degree of enjoyment because the participants chose this condition over those that lacked such a contingency. The ventral striatum and midbrain were activated only when action-outcome contingency was present. Thus, the intrinsic value of action was represented by an increase in ventral striatal and midbrain activation.
一种行为的内在价值是指即便某种行为没有明确的结果，人们在体验该行为时仍能感受到的一种内在的愉悦感。先前的研究表明，奖赏网络中的一种常见评估机制可能负责处理实现结果和获得外部奖励的内在价值。然而，行为的内在价值在神经层面是如何表征的仍不清楚。我们假设，行为的内在价值由行为与结果之间的偶然性决定，即该行为是可控的，且行为的结果可通过这种反馈进行评估。因此，奖赏网络应该会被激活，这反映了行为内在价值的产生。为了验证这一假设，我们进行了一项功能性磁共振成像（fMRI）研究，该研究采用了一款秒表游戏，其中行为与结果之间的偶然性是被操控的。这项实验有36名健康志愿者参与，秒表游戏有四个版本，这些版本操控了可控性（参与者感觉自己在控制秒表）和结果（一个信号，让参与者看到自己行为的结果）。在fMRI实验之后进行了一项自由选择实验，以探究参与者对每个游戏的偏好程度。结果显示，具有行为与结果偶然性的秒表游戏引发了更大程度的愉悦感，因为与那些缺乏这种偶然性的游戏相比，参与者选择了这种情况。只有当存在行为与结果偶然性时，腹侧纹状体和中脑才会被激活。因此，行为的内在价值通过腹侧纹状体和中脑激活的增加来体现。
