A Role for Locus Coeruleus in Information Processing

决策往往取决于对潜在结果的概率和价值的表述。但是，在动态环境中维护这些变量的准确表示可能很困难。在这样的环境中保持准确表达的大多数策略都会在经历不可预测的结果后进行更新。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陈述产生多大影响。原则上，这一决定应考虑到至少两种形式的环境变异性。持续的环境随机性，或噪声，导致每个结果都是下一个的糟糕预测因素，这表明每个新的结果对现有代表的影响应该只是最小的。另一种形式的变异性是由于环境的突然变化，或变化点。这样的变化点可能会使历史结果与未来的结果无关，这表明陈述应该受到新结果的高度影响。这两种形式的可变性都会导致偏离预期结果，然而，这两种类型的可变性意味着相反的行动方向。之前的研究表明，人和动物能够在嘈杂和不断变化的环境中近乎最佳地更新表征，这表明大脑有一种机制，可以利用环境的变异性将影响分配给新的结果。然而，人们对其潜在的神经机制知之甚少。一个重要的假说认为，脑干蓝斑核(LC)提供了一种不确定的信号，可以用来自适应地调整传入的感觉信息对知觉加工的影响。然而，这一理论及其与更一般形式的信念更新的关系还有待于实证检验。这项提议的目的是为我提供最先进的实验技术方面的培训，这些技术结合了定量的行为测量和神经生理测量。这项训练将允许我测试这样一个假设，即LC编码与感知噪声和变化点相关的关键计算变量，这些变量用于分配对输入信息的影响。拟议的实验是基于我之前在研究生工作中开发的行为和计算方法。第一个具体目标是描述瞳孔直径和液晶活动之间的关系。第二个目的是测试LC活动是否反映了相同受试者在执行表征更新任务时对结果影响的行为和计算指标。这些目标将为LC在复杂的适应性行为中所扮演的角色提供新的见解。

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.