Neural Economics and Biological Substrates of Valuation

描述（由申请人提供）：持续的经济评估是任何系统的核心功能，必须与有限的，有限的资源，即所有移动的生物。对神经评估机制的需求源于移动的生物的神经系统可获得的信息的绝对广度和多样性，以及感官刺激和可能的行为输出必须优先考虑的事实。这就提出了一个基本的信息处理问题：必须将截然不同的刺激和行为输出置于某种共同的评价尺度上。如果神经系统中没有内部评估系统，生物将无法评估本质上不同的事件的相对价值，如饮水，闻到食物，扫描捕食者，安静地坐在阳光下，等等。为了决定一个适当的行为，神经系统必须估计这些潜在行为或刺激中的每一个的价值，将其转换为一个共同的尺度（货币），并使用这个尺度来确定一个行动过程。这个问题早已被行为心理学家和经济学家所重视;然而，直到最近才在人类实验中解决了潜在的神经基质。中脑多巴胺系统和它们投射到的目标神经结构现在已经被确定为参与对未来奖励事件的评估。特别是，计算工作已经表明，这些多巴胺神经元的子集编码和分发预测误差信号，代表实际奖励和预测奖励之间的持续差异。这种多巴胺能功能的预测误差模型现在已经导致了预测人类行为的行为模型。这些任务提出了一个问题：“人类如何评价奖励刺激的持续变化？“，这是一个对药物滥用有重要影响的问题。然而，目前还没有生物学测量与这些基于模型的行为预测相关联。这项提案的长期目标是在执行顺序决策任务期间使用功能性磁共振成像（fMRI）来探测与人类表现相关的大脑反应。这项工作将为人类大脑中存在的估值机制提供基本见解。

DESCRIPTION (provided by applicant): Ongoing economic evaluation is a central function for any system that must operate with limited, finite resources, that is, all mobile creatures. The need for neural valuation mechanisms arises from the sheer breadth and variety of information available to a mobile creature's nervous system, and the fact that sensory stimuli and possible behavioral output must be prioritized. This presents a fundamental information-processing problem: vastly different stimuli and behavioral output must be placed on some common valuation scale. Without internal valuation systems in the nervous system, a creature would be unable to assess the relative value of intrinsically different events like drinking water, smelling food, scanning for predators, sitting quietly in the sun, and so forth. To decide on an appropriate behavior, the nervous system must estimate the value of each of these potential actions or stimuli, convert it to a common scale (currency), and use this scale to determine a course of action. This issue has long been appreciated by behavioral psychologists and economists; however, only recently have the underlying neural substrates been addressed experimentally in humans. Midbrain dopamine systems and the target neural structures to which they project have now been identified as participating in the valuation of future rewarding events. In particular, computational work has shown that a subset of these dopamine neurons encode and distribute a prediction error signal representing the ongoing difference between actual reward and predicted reward. This prediction error model of dopaminergic function has now led to behavioral models that predict human behavior on sequential decision-making tasks. These tasks ask the question: "How do humans value ongoing changes in rewarding stimuli?", a question with important implications for drug abuse. However, there has been no biological measure to correlate with these model-based behavioral predictions. The long-term goal of this proposal is to use functional magnetic resonance imaging (fMRI) during the execution of sequential decision tasks to probe the brain responses that correlate with human performance. This work will provide fundamental insights into valuations mechanisms present in human brains.