Seo Hyojung, Lee Daeyeol
Department of Neurobiology, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
J Neurosci. 2009 Mar 18;29(11):3627-41. doi: 10.1523/JNEUROSCI.4726-08.2009.
Human behaviors can be more powerfully influenced by conditioned reinforcers, such as money, than by primary reinforcers. Moreover, people often change their behaviors to avoid monetary losses. However, the effect of removing conditioned reinforcers on choices has not been explored in animals, and the neural mechanisms mediating the behavioral effects of gains and losses are not well understood. To investigate the behavioral and neural effects of gaining and losing a conditioned reinforcer, we trained rhesus monkeys for a matching pennies task in which the positive and negative values of its payoff matrix were realized by the delivery and removal of a conditioned reinforcer. Consistent with the findings previously obtained with non-negative payoffs and primary rewards, the animal's choice behavior during this task was nearly optimal. Nevertheless, the gain and loss of a conditioned reinforcer significantly increased and decreased, respectively, the tendency for the animal to choose the same target in subsequent trials. We also found that the neurons in the dorsomedial frontal cortex, dorsal anterior cingulate cortex, and dorsolateral prefrontal cortex often changed their activity according to whether the animal earned or lost a conditioned reinforcer in the current or previous trial. Moreover, many neurons in the dorsomedial frontal cortex also signaled the gain or loss occurring as a result of choosing a particular action as well as changes in the animal's behaviors resulting from such gains or losses. Thus, primate medial frontal cortex might mediate the behavioral effects of conditioned reinforcers and their losses.
与初级强化物相比，诸如金钱等条件性强化物对人类行为的影响可能更为强烈。此外，人们常常会改变自己的行为以避免金钱损失。然而，在动物身上尚未探究去除条件性强化物对选择行为的影响，而且介导收益和损失行为效应的神经机制也尚未得到充分理解。为了研究获得和失去条件性强化物的行为和神经效应，我们训练恒河猴进行一种匹配硬币任务，在此任务中，其收益矩阵的正负价值通过给予和去除一种条件性强化物来实现。与先前使用非负收益和初级奖励所获得的结果一致，动物在此任务中的选择行为近乎最优。尽管如此，条件性强化物的获得和损失分别显著增加和降低了动物在后续试验中选择同一目标的倾向。我们还发现，背内侧前额叶皮层、背侧前扣带回皮层和背外侧前额叶皮层中的神经元活动常常根据动物在当前或先前试验中是获得还是失去条件性强化物而发生变化。此外，背内侧前额叶皮层中的许多神经元还会发出信号，表明因选择特定行动而导致的收益或损失，以及此类收益或损失所引起的动物行为变化。因此，灵长类动物的内侧前额叶皮层可能介导条件性强化物及其损失的行为效应。
