Zhang Pei-Wen, Qu Xiu-Juan, Qian Shu-Fang, Wang Xin-Bo, Wang Rui-Di, Li Qiu-Yue, Liu Shi-Yu, Chen Lihong, Liu Dong-Qiang
Research Center of Brain and Cognitive Neuroscience, Liaoning Normal University, Dalian, China.
Front Neurosci. 2018 Jul 31;12:516. doi: 10.3389/fnins.2018.00516. eCollection 2018.
Recent BOLD-fMRI studies have revealed spatial distinction between variability- and mean-based between-condition differences, suggesting that BOLD variability could offer complementary and even orthogonal views of brain function with traditional activation. However, these findings were mainly observed in block-designed fMRI studies. As block design may not be appreciate for characterizing the low-frequency dynamics of BOLD signal, the evidences suggesting the distinction between BOLD variability and mean are less convincing. Based on the high reproducibility of signal variability modulation between continuous eyes-open (EO) and eyes-closed (EC) states, here we employed EO/EC paradigm and BOLD-fMRI to compare variability- and mean-based EO/EC differences while the subjects were in light. The comparisons were made both on block-designed and continuous EO/EC data. Our results demonstrated that the spatial patterns of variability- and mean-based EO/EC differences were largely distinct with each other, both for block-designed and continuous data. For continuous data, increases of BOLD variability were found in secondary visual cortex and decreases were mainly in primary auditory cortex, primary sensorimotor cortex and medial nuclei of thalamus, whereas no significant mean-based differences were observed. For the block-designed data, the pattern of increased variability resembled that of continuous data and the negative regions were restricted to medial thalamus and a few clusters in auditory and sensorimotor networks, whereas activation regions were mainly located in primary visual cortex and lateral nuclei of thalamus. Furthermore, with the expanding window analyses we found variability results of continuous data exhibited a rather slower dynamical process than typically considered for task activation, suggesting block design is less optimal than continuous design in characterizing BOLD variability. In sum, we provided more solid evidences that variability-based modulation could represent orthogonal views of brain function with traditional mean-based activation.
最近的血氧水平依赖性功能磁共振成像（BOLD-fMRI）研究揭示了基于变异性和基于均值的条件间差异在空间上的区别，这表明BOLD变异性可为脑功能提供与传统激活互补甚至正交的视角。然而，这些发现主要是在采用组块设计的fMRI研究中观察到的。由于组块设计可能不太适合表征BOLD信号的低频动态变化，因此表明BOLD变异性与均值之间存在区别的证据不太有说服力。基于连续睁眼（EO）和闭眼（EC）状态之间信号变异性调制的高重现性，我们在此采用EO/EC范式和BOLD-fMRI来比较在清醒状态下基于变异性和基于均值的EO/EC差异。对组块设计和连续的EO/EC数据均进行了比较。我们的结果表明，无论是组块设计数据还是连续数据，基于变异性和基于均值的EO/EC差异的空间模式在很大程度上彼此不同。对于连续数据，在次级视觉皮层中发现BOLD变异性增加，而减少主要出现在初级听觉皮层、初级感觉运动皮层和丘脑内侧核，而基于均值的差异未观察到显著变化。对于组块设计数据，变异性增加的模式与连续数据相似，负性区域局限于丘脑内侧以及听觉和感觉运动网络中的少数簇，而激活区域主要位于初级视觉皮层和丘脑外侧核。此外，通过扩展窗口分析，我们发现连续数据的变异性结果显示出比通常认为的任务激活更缓慢的动态过程，这表明在表征BOLD变异性方面，组块设计不如连续设计理想。总之，我们提供了更确凿的证据，即基于变异性的调制可以代表与传统基于均值的激活正交的脑功能视角。
