Neural mechanisms of reward processing and emotion

眶额皮质（OFC）和杏仁核之间的相互作用对于学习以及随后改变刺激和强化之间的关联至关重要。然而，直到我们在本报告所述期间的工作之前，眶额皮层在这种奖励处理中的确切作用以及杏仁核的贡献（如果有的话）仍然不清楚。我们研究了在灵活的奖励加工任务中，OFC或杏仁核损伤的受试者的奖励加工：对象反转学习。我们发现，与对照组和杏仁核病变组相比，眶额皮层病变组在使用正确的试验指导后续选择方面表现较差。相比之下，杏仁核损伤的受试者比对照组从错误后正确执行的试验中获益更多。这些发现表明，眶额皮层和杏仁核对奖赏加工的贡献不同，奖赏加工是重性抑郁症患者中断的一种信息加工。 这些发现支持了OFC特别代表共同货币价值的观点。一个共同的价值体系允许对不同类型的奖励进行比较，以便做出最有利的选择。本项目的下一阶段是测试OFC代表用于决策的值的想法。这种评价必须独立于任何感官模式，而且只要有多种竞争结果，而不是只有一种结果是可能的，它就必须开始运作。在即将到来的一年中，我们将开始更深入的，机械的检查OFC和MFC，以检查它们的关系，预测结果为不同类型的刺激-结果映射，以及杏仁核在这一功能中的作用。这些实验延续了上述工作，以及神经心理学和神经生理学的发现，这些发现表明，价值是根据来自杏仁核的输入在眶额皮层中编码的，而在杏仁核缺失的情况下，将刺激与结果联系起来的关联编码就会中断。我们将研究OFC和MFC神经元之前和之后的选择性兴奋毒性杏仁核病变。如果联合价值编码需要杏仁核，那么在杏仁核损伤之前，眶额皮层和前额叶皮层的神经活动应该反映出同一货币中物体的价值，但在杏仁核损伤之后，这种活动应该被中断或消失。我们还将比较OFC和MFC对熟悉物体和新物体的联想评价，表现为受试者学习最初中性物体的价值，以及杏仁核对这两种评价的贡献。

The interaction between the orbitofrontal cortex (OFC) and the amygdala is critical for learning and subsequently changing associations between stimuli and reinforcement. However, the precise role of the OFC in this kind of reward processing and the contribution of the amygdala, if any, remained unclear until our work during this reporting period. We studied reward processing in subjects with either OFC or amygdala lesions in a task of flexible reward processing: object reversal learning. We found that subjects with OFC lesions were, compared with control subjects and subjects with amygdala lesions, poor at using correctly performed trials to guide subsequent choices. Subjects with amygdala lesions, by contrast, benefited more than controls from correctly performed trials that followed an error. These findings show that the OFC and the amygdala make different contributions to reward processing, one of the kinds of information processing disrupted in patients with major depressive disorder. These findings support the idea that OFC, in particular, represents value in a common currency. A common value system allows the comparison of different kinds of rewards so that the most advantageous choices can be made. The next stage of the present project is to test the idea that the OFC represents the values used for decision making. This valuation must be independent of any sensory modality and it must come into operation whenever there are multiple competing outcomes, as opposed to when only one type of outcome is possible. In the upcoming year we will begin a more in-depth, mechanistic examination of OFC and MFC in order to examine their relationship to predicted outcome for different types of stimulus-outcome mappings, as well as the role of the amygdala in this function. These experiments follow up the work described above, as well as neuropsychological and neurophysiological findings suggesting that value is encoded in the OFC based on inputs from the amygdala, and that, in the absence of the amygdala, the associative encoding linking stimuli with outcomes becomes disrupted. We will study OFC and MFC neurons before and after selective excitotoxic amygdala lesions. If associative value encoding requires the amygdala, then before amygdala lesions the neural activity in OFC and MFC should reflect the value of objects in a common currency, but after amygdala lesions this activity should be disrupted or disappear. We will also compare OFC and MFC associative valuations for both familiar objects and novel ones, presented as subjects learn the value of an initially neutral object, as well as the contribution of the amygdala to both kinds of valuations.