Neural mechanisms of reward processing and emotion

眼窝前额皮质（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，OFC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），直到我们在本报告期间的工作才得以明确。我们研究了有OFC或杏仁核损伤的受试者在灵活的奖励处理任务中的奖励处理：对象逆转学习。我们发现，与对照组和杏仁核病变的受试者相比，OFC病变的受试者在使用正确执行的试验来指导后续选择方面表现较差。相比之下，扁桃体受损的受试者从正确执行错误后的试验中获益比对照组多。这些发现表明，OFC和杏仁核对奖励处理有不同的贡献，奖励处理是重度抑郁症患者的一种信息处理中断。这些发现支持了OFC尤其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代表用于决策的价值的想法。这种评估必须独立于任何感官模式，并且必须在存在多种竞争结果时开始运作，而不是在只有一种结果可能的情况下。在接下来的一年里，我们将开始对OFC和MFC进行更深入、更机械的研究，以检验它们与不同类型的刺激-结果映射的预测结果之间的关系，以及杏仁核在这一功能中的作用。这些实验跟进了上述工作，以及神经心理学和神经生理学的发现，这些发现表明，价值是基于杏仁核的输入在OFC中编码的，并且，在杏仁核缺失的情况下，将刺激与结果联系起来的联想编码被破坏了。我们将研究选择性兴奋毒性杏仁核病变前后的OFC和MFC神经元。如果联想值编码需要杏仁核，那么在杏仁核病变前，OFC和MFC的神经活动应该反映物体在共同货币中的价值，但在杏仁核病变后，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，当受试者学习最初中性物体的价值时，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.