皮质醇觉醒反应预测脑功能

The human HPA activity is characterized by an increase in the free cortisol levels within the first 30 minutes after morning awakening. The cortisol awakening response (CAR) have higher intra-individual statbility, and are usually regarded as a trait of neuroendocrine activity, and have close relationship with brain structures and functions. However, CAR also fluctuate across days, i.e., CAR have the characteristic of state variation. Recent hypothesis assumed that CAR can predict brain function of the same day (Law et al., 2013). Results of our lab provide first evidence for this hypothesis, i.e., CAR predicts intrinsic functional connectivity of the medial prefrontal cortex in the afternoon of the same day (Wu et al., 2015). The current project aims at whether and how psychophysiological indexes in which CAR act as the core predict executive functions (working memory, attentional shift, response inhibition and error processing)，emotional response and emotional regulation. From the academic point of view, the key brain areas underling these functions, i.e., prefrontal cortex and amygdala, are core brain areas as both regulating HPA activity and the target of cortisol. From the practical view of point, these brain functions are among these core psychological components of some critical operations. How to predict whether the operators are qualified with the risk-taking critical operations of the current day is one of the main concerns in these practical fields. The current project will provide scientific foundation for building the objective and effective post-morning awakening screening system about cognitive functions.

皮质醇水平在晨醒后短暂升高，这被称为皮质醇觉醒反应（CAR）。CAR具有较大的个体内稳定性，常被用作神经内分泌活动的特质，与脑结构和功能密切相关。每天的CAR水平也会发生波动，即CAR具有状态性；Law等（2013）假设：CAR状态能预测当天脑功能。我们的结果为该假设首次提供证据：CAR能预测当天下午以内侧前额叶为核心的脑功能连接强度 (Wu et al., 2015)，然而该研究仅仅关注静息状态。本项目拟研究以CAR为核心的生理心理指标是否预测当天的执行功能（工作记忆、注意转换、反应抑制、错误加工等）、情绪反应和情绪调节功能。从学术角度，负责这些功能的前额叶-杏仁核环路既是神经内分泌调控的重要枢纽，也是皮质醇的重要靶脑区。从应用角度，这些脑功能是胜任一些关键作业的要素；提前预测作业者是否胜任当天的高危作业，是有关行业的关注重点，本项目研究将为建立客观的晨醒后筛查体系奠定科学基础。

在昼夜交替的影响下，人体神经-内分泌系统也呈现出相应的节律反应。在早晨醒来之后的一个小时之内，人体会大量分泌一种叫做皮质醇的应激激素（俗称压力激素），并迅速达到一天中的峰值，然后很快回落，这个现象被称之为“皮质醇觉醒反应”（Cortisol Awakening Response，以下简称CAR）。CAR这一独特的神经-内分泌活动，跟人类的心理行为、学习与工作效率以及精神健康水平等密切相关，但是其底层的认知神经生物机理不明、理论模型与实证研究匮乏。.本项目对此开展了一系列研究，从多个角度证明CAR为当天的认知功能提供了神经内分泌资源，这些结果支持了Law等（2013）的假设，也为“一日之计在于晨”提供了实证证据。CAR越高，静息状态下前额叶中央区左侧皮层活动性越强，这个结果提示晨醒后皮质醇调动与目标趋近行为相关；CAR越大，负性情绪诱发的神经活动（LPP波幅，晚正成分）越小，这个结果表明晨起皮质醇觉醒反应可能为前额叶的情绪调控提供了动能，从而降低了对于负性情绪刺激的神经反应；CAR越大，反应抑制相关的N2波幅越大，说明晨起皮质醇可能为前额叶反应监控提供了动能。fMRI研究则进一步证明CAR的动能效应可能是通过前摄性地提高有关脑区（比如海马）和前额叶的局部神经活动效率和相关脑网络的功能连接实现的。.但进一步的研究结果发现两者呈现应激领域经典的倒U型曲线关系趋势，比如CAR与NoGo误报率以及错误监控相关的ERN波幅呈现倒U型曲线关系。.本项目研究结果为理解晨起皮质醇反应和认知功能的关系及其脑机制，提供了实证证据。