Modulation of Brain Resting-State Networks by Sad Mood Induction

BackgroundThere is growing interest in the nature of slow variations of the blood oxygen level-dependent (BOLD) signal observed in functional MRI resting-state studies. In humans, these slow BOLD variations are thought to reflect an underlying or intrinsic form of brain functional connectivity in discrete neuroanatomical systems. While these ��resting-state networks�� may be relatively enduring phenomena, other evidence suggest that dynamic changes in their functional connectivity may also emerge depending on the brain state of subjects during scanning.Methodology/Principal FindingsIn this study, we examined healthy subjects (n = 24) with a mood induction paradigm during two continuous fMRI recordings to assess the effects of a change in self-generated mood state (neutral to sad) on the functional connectivity of these resting-state networks (n = 24). Using independent component analysis, we identified five networks that were common to both experimental states, each showing dominant signal fluctuations in the very low frequency domain (��0.04 Hz). Between the two states, we observed apparent increases and decreases in the overall functional connectivity of these networks. Primary findings included increased connectivity strength of a paralimbic network involving the dorsal anterior cingulate and anterior insula cortices with subjects' increasing sadness and decreased functional connectivity of the ��default mode network��.Conclusions/SignificanceThese findings support recent studies that suggest the functional connectivity of certain resting-state networks may, in part, reflect a dynamic image of the current brain state. In our study, this was linked to changes in subjective mood.**研究背景**：目前，功能磁共振成像（functional MRI, fMRI）静息态研究中观测到的血氧水平依赖（blood oxygen level-dependent, BOLD）信号慢波动的本质日益受到关注。在人体中，这类缓慢的BOLD信号波动被认为反映了离散神经解剖系统中潜在的固有脑功能连接模式。尽管这类‘静息态网络（resting-state networks）’或许是相对持久的现象，但其他研究证据表明，其功能连接的动态变化也可能随扫描过程中受试者的脑状态而发生改变。 **研究方法与主要结果**：本研究中，我们借助情绪诱发范式，对24名健康受试者开展了两次连续功能磁共振成像扫描，以探究自我产生的情绪状态（从中性转为悲伤）变化对这类静息态网络功能连接的影响。本研究采用独立成分分析（independent component analysis, ICA），识别出两种实验状态下共有的5个网络，每个网络在极低频域（<0.04 Hz）均呈现出显著的信号波动。在两种实验状态之间，我们观察到这些网络的整体功能连接出现明显的增强与减弱。主要研究结果包括：随着受试者悲伤情绪程度加深，一个涉及背侧前扣带回与前岛叶皮层的边缘旁网络的连接强度显著增强；而默认模式网络（default mode network）的功能连接则出现减弱。 **研究结论与意义**：本研究结果佐证了近期相关研究的结论，即特定静息态网络的功能连接在一定程度上能够反映当前脑状态的动态特征；在本研究中，这一关联与受试者的主观情绪变化密切相关。