A Role for Locus Coeruleus in Information Processing

决策通常取决于对潜在结果的概率和价值的表示。然而，在动态环境中保持这些变量的准确表示可能是困难的。大多数在这种环境中保持准确表征的策略都会在经历不可预测的结果后更新它们。 这些方法的一个关键挑战是决定不可预测的结果应该对现有的表示产生多大的影响。原则上，这一决定应考虑到至少两种形式的环境可变性。持续的环境随机性，或噪音，导致每个结果都是下一个结果的坏预测，这表明每个新结果对现有表征的影响应该很小。另一种形式的可变性是由于环境的突然变化或变点而发生的。这种变化点可以使历史结果与未来结果无关，这表明表征应该受到新结果的高度影响。这两种形式的变异性导致偏离预期结果，然而，这两种类型的变异性表明相反的行动方针。先前的研究表明，人类和动物能够在嘈杂和不断变化的环境中以近乎最佳的方式更新表征，这表明大脑有一种利用环境变化来影响新结果的机制。然而，人们对潜在的神经机制知之甚少。一个突出的假设涉及脑干蓝斑核（LC）在提供一个不确定性信号，可用于自适应地调整传入的感觉信息对感知处理的影响。然而，这一理论及其与更普遍形式的信念更新的关系还有待于实证检验。 这个建议的目的是为我提供最先进的实验技术，结合联合收割机定量行为和神经生理学测量的培训。这种训练将使我能够测试LC编码与感知噪声和变点相关的关键计算变量的假设，这些变量用于将影响分配给传入信息。所提出的实验是基于行为和计算方法，我以前在我的研究生工作。第一个具体目标是表征瞳孔直径和LC活性之间的关系。 第二个目标将测试LC活动是否反映了行为和计算指标的结果影响，在相同的主题，而他们执行的表征更新任务。 这些目标将为LC在复杂的适应性行为中的作用提供新的见解。

Decisions often depend on representations about the probability and value of potential outcomes. However, maintaining accurate representations of these variables can be difficult in a dynamic environment. Most strategies for maintaining accurate representations in such an environment update them after experiencing unpredicted outcomes. A key challenge for these approaches is to decide how much influence that unpredicted outcomes should have on existing representations. In principle, this decision should take into account at least two forms of environmental variability. Persistent environmental stochasticity, or noise, leads each outcome to be a bad predictor of the next suggesting that each new outcome should have only a minimal influence on an existing representation. Another form of variability occurs due to sudden environmental changes, or change-points. Such change-points can render historical outcomes irrelevant to future ones, suggesting that representations should be highly influenced by a new outcome. Both forms of variability lead to deviations from expected outcomes, however the two types of variability suggest opposite courses of action. Previous work has shown that people and animals are capable of updating representations nearly optimally in noisy and changing environments, suggesting that the brain has a mechanism for using environmental variability to assign influence to new outcomes. However, little is known about the underlying neural mechanisms. One prominent hypothesis implicates the brainstem nucleus locus coeruleus (LC) in providing an uncertainty signal that can be used to adaptively adjust the influence of incoming sensory information on perceptual processing. However, this theory ¿ and its relationship to more general forms of belief updating ¿ has yet to be tested empirically. The goal of this proposal is to provide me with training on state-of-the-art experimental techniques that combine quantitative behavioral and neurophysiological measurements. This training will allow me to test the hypothesis that LC encodes key computational variables related to perceived noise and change-points that are used to assign influence to incoming information. The proposed experiments are based on behavioral and computational approaches that I developed previously in my graduate work. The first specific aim is to characterize the relationship between pupil diameter and LC activity. The second aim will test whether LC activity reflects behavioral and computational metrics of outcome influence in the same subjects while they perform a representation updating task. Together these Aims will provide new insights about the role of LC in complex, adaptive behavior.