Graduate Institute of Biomedical Engineering and Bioinformatics, National Taiwan University, Taipei, Taiwan.
PLoS One. 2011;6(5):e18954. doi: 10.1371/journal.pone.0018954. Epub 2011 May 24.
Visual processing network is one of the functional networks which have been reliably identified to consistently exist in human resting brains. In our work, we focused on this network and investigated the intrinsic properties of low frequency (0.01-0.08 Hz) fluctuations (LFFs) during changes of visual stimuli. There were two main questions to be discussed in this study: intrinsic properties of LFFs regarding (1) interactions between visual stimuli and resting-state; (2) impact of repetition rate of visual stimuli.
METHODOLOGY/PRINCIPAL FINDINGS: We analyzed scanning sessions that contained rest and visual stimuli in various repetition rates with a novel method. The method included three numerical approaches involving ICA (Independent Component Analyses), fALFF (fractional Amplitude of Low Frequency Fluctuation), and Coherence, to respectively investigate the modulations of visual network pattern, low frequency fluctuation power, and interregional functional connectivity during changes of visual stimuli. We discovered when resting-state was replaced by visual stimuli, more areas were involved in visual processing, and both stronger low frequency fluctuations and higher interregional functional connectivity occurred in visual network. With changes of visual repetition rate, the number of areas which were involved in visual processing, low frequency fluctuation power, and interregional functional connectivity in this network were also modulated.
CONCLUSIONS/SIGNIFICANCE: To combine the results of prior literatures and our discoveries, intrinsic properties of LFFs in visual network are altered not only by modulations of endogenous factors (eye-open or eye-closed condition; alcohol administration) and disordered behaviors (early blind), but also exogenous sensory stimuli (visual stimuli with various repetition rates). It demonstrates that the intrinsic properties of LFFs are valuable to represent physiological states of human brains.
视觉处理网络是在人类静息大脑中可靠识别的功能网络之一。在我们的工作中，我们专注于这个网络，并研究了在视觉刺激变化过程中低频（0.01-0.08Hz）波动（LFFs）的内在特性。在这项研究中有两个主要问题需要讨论：LFFs 的内在特性涉及（1）视觉刺激与静息状态之间的相互作用；（2）视觉刺激重复率的影响。
方法/主要发现：我们使用一种新方法分析了包含不同重复率的静息和视觉刺激的扫描会话。该方法包括三种数值方法，涉及 ICA（独立成分分析）、fALFF（低频波动的分数幅度）和相干性，分别研究视觉网络模式、低频波动功率和视觉刺激变化过程中区域间功能连接的调制。我们发现，当静息状态被视觉刺激取代时，更多的区域参与了视觉处理，视觉网络中出现了更强的低频波动和更高的区域间功能连接。随着视觉重复率的变化，参与视觉处理的区域数量、该网络中的低频波动功率和区域间功能连接也发生了变化。
结论/意义：结合先前文献的结果和我们的发现，视觉网络中 LFFs 的内在特性不仅受到内源性因素（睁眼或闭眼状态；酒精摄入）和紊乱行为（早期失明）调制的影响，还受到外源性感觉刺激（各种重复率的视觉刺激）的影响。这表明 LFFs 的内在特性对于代表人类大脑的生理状态具有重要价值。
