Wallis Jonathan D
University of California at Berkeley, Helen Wills Neuroscience Institute, Berkeley, CA, 94720, USA.
Ann N Y Acad Sci. 2007 Dec;1121:447-60. doi: 10.1196/annals.1401.009. Epub 2007 Sep 10.
This chapter aims to address two questions relating to the role of the prefrontal cortex (PFC) in reward-guided choice behavior. First, do PFC neurons encode rewards per se, or are they encoding behavioral sequelae of reward? To address this, we recorded simultaneously from multiple PFC subregions, with the rationale that neuronal selectivity that directly encoded the reward outcome should occur before selectivity that reflected reward-related sequelae. Our results indicate that neurons in the orbitofrontal cortex (OFC) encode reward information before neurons in the dorsolateral PFC (DLPFC). Furthermore, whereas DLPFC neurons encoded both the upcoming response as well as the expected reward, OFC neurons encoded the reward alone. Our interpretation of these results is that the OFC encodes the reward and passes this information to the DLPFC, which uses it to determine the behavioral response. The second question is whether the encoding is specific to the reward outcome or reflective of a more abstract value signal that could facilitate decision making. We examined this by determining whether the PFC encodes other types of information relevant to decision making, such as probability of success and effort. We found that many PFC neurons encoded at least one of these variables, but neurons in the OFC and the medial PFC (MPFC) encoded combinations of the variables indicative of encoding an abstract value signal. This signal could provide decision making with flexibility and a capacity to deal with novelty, which are two of the hallmark features of prefrontal function. Future research will focus on delineating the differential contributions of the OFC and the MPFC to decision making.
本章旨在探讨与前额叶皮质（PFC）在奖励引导的选择行为中的作用相关的两个问题。首先，PFC神经元是直接编码奖励本身，还是编码奖励的行为后果？为了解决这个问题，我们同时记录了多个PFC子区域的活动，其依据是直接编码奖励结果的神经元选择性应该出现在反映奖励相关后果的选择性之前。我们的结果表明，眶额皮质（OFC）中的神经元比背外侧PFC（DLPFC）中的神经元更早地编码奖励信息。此外，虽然DLPFC神经元既编码即将到来的反应，也编码预期的奖励，但OFC神经元只编码奖励。我们对这些结果的解释是，OFC对奖励进行编码，并将此信息传递给DLPFC，DLPFC利用该信息来确定行为反应。第二个问题是，这种编码是特定于奖励结果，还是反映了一种更抽象的价值信号，这种信号可以促进决策。我们通过确定PFC是否编码与决策相关的其他类型信息（如成功概率和努力程度）来对此进行研究。我们发现，许多PFC神经元至少编码了这些变量中的一个，但OFC和内侧PFC（MPFC）中的神经元编码了这些变量的组合，这表明它们编码的是一种抽象的价值信号。这种信号可以为决策提供灵活性和应对新情况的能力，而这是前额叶功能的两个标志性特征。未来的研究将集中于阐明OFC和MPFC对决策的不同贡献。
