Hodkinson Duncan J, O'Daly Owen, Zunszain Patricia A, Pariante Carmine M, Lazurenko Vitaly, Zelaya Fernando O, Howard Matthew A, Williams Steven C R
Department of Neuroimaging Sciences, Institute of Psychiatry, King's College London, London, UK.
Laboratory of Stress, Psychiatry and Immunology, Department of Psychological Medicine, Institute of Psychiatry, King's College London, London, UK.
J Cereb Blood Flow Metab. 2014 Sep;34(9):1493-9. doi: 10.1038/jcbfm.2014.109. Epub 2014 Jun 18.
Diurnal rhythms have been observed in human behaviors as diverse as sleep, olfaction, and learning. Despite its potential impact, time of day is rarely considered when brain responses are studied by neuroimaging techniques. To address this issue, we explicitly examined the effects of circadian and homeostatic regulation on functional connectivity (FC) and regional cerebral blood flow (rCBF) in healthy human volunteers, using whole-brain resting-state functional magnetic resonance imaging (rs-fMRI) and arterial spin labeling (ASL). In common with many circadian studies, we collected salivary cortisol to represent the normal circadian activity and functioning of the hypothalamic-pituitary-adrenal (HPA) axis. Intriguingly, the changes in FC and rCBF we observed indicated fundamental decreases in the functional integration of the default mode network (DMN) moving from morning to afternoon. Within the anterior cingulate cortex (ACC), our results indicate that morning cortisol levels are negatively correlated with rCBF. We hypothesize that the homeostatic mechanisms of the HPA axis has a role in modulating the functional integrity of the DMN (specifically, the ACC), and for the purposes of using fMRI as a tool to measure changes in disease processes or in response to treatment, we demonstrate that time of the day is important when interpreting resting-state data.
人们已经在睡眠、嗅觉和学习等多种人类行为中观察到昼夜节律。尽管其具有潜在影响，但在通过神经成像技术研究大脑反应时，很少考虑一天中的时间。为了解决这个问题，我们使用全脑静息态功能磁共振成像（rs-fMRI）和动脉自旋标记（ASL），明确研究了昼夜节律和稳态调节对健康人类志愿者功能连接（FC）和局部脑血流量（rCBF）的影响。与许多昼夜节律研究一样，我们收集唾液皮质醇以代表下丘脑-垂体-肾上腺（HPA）轴的正常昼夜活动和功能。有趣的是，我们观察到的FC和rCBF变化表明，从早晨到下午，默认模式网络（DMN）的功能整合基本下降。在前扣带回皮质（ACC）内，我们的结果表明早晨皮质醇水平与rCBF呈负相关。我们假设HPA轴的稳态机制在调节DMN（特别是ACC）的功能完整性方面发挥作用，并且为了将功能磁共振成像用作测量疾病过程变化或治疗反应的工具，我们证明在解释静息态数据时一天中的时间很重要。
