Zou Qi-Hong, Zhu Chao-Zhe, Yang Yihong, Zuo Xi-Nian, Long Xiang-Yu, Cao Qing-Jiu, Wang Yu-Feng, Zang Yu-Feng
State Key Laboratory of Cognitive Neuroscience and Learning, Beijing Normal University, PR China.
J Neurosci Methods. 2008 Jul 15;172(1):137-41. doi: 10.1016/j.jneumeth.2008.04.012. Epub 2008 Apr 22.
Most of the resting-state functional magnetic resonance imaging (fMRI) studies demonstrated the correlations between spatially distinct brain areas from the perspective of functional connectivity or functional integration. The functional connectivity approaches do not directly provide information of the amplitude of brain activity of each brain region within a network. Alternatively, an index named amplitude of low-frequency fluctuation (ALFF) of the resting-state fMRI signal has been suggested to reflect the intensity of regional spontaneous brain activity. However, it has been indicated that the ALFF is also sensitive to the physiological noise. The current study proposed a fractional ALFF (fALFF) approach, i.e., the ratio of power spectrum of low-frequency (0.01-0.08 Hz) to that of the entire frequency range and this approach was tested in two groups of resting-state fMRI data. The results showed that the brain areas within the default mode network including posterior cingulate cortex, precuneus, medial prefrontal cortex and bilateral inferior parietal lobule had significantly higher fALFF than the other brain areas. This pattern was consistent with previous neuroimaging results. The non-specific signal components in the cistern areas in resting-state fMRI were significantly suppressed, indicating that the fALFF approach improved the sensitivity and specificity in detecting spontaneous brain activities. Its mechanism and sensitivity to abnormal brain activity should be evaluated in the future studies.
大多数静息态功能磁共振成像（fMRI）研究从功能连接或功能整合的角度证明了空间上不同的脑区之间的相关性。功能连接方法并不能直接提供网络内每个脑区脑活动幅度的信息。另外，有人提出静息态fMRI信号的低频波动幅度（ALFF）指数来反映区域自发脑活动的强度。然而，有研究表明ALFF对生理噪声也很敏感。本研究提出了一种分数ALFF（fALFF）方法，即低频（0.01-0.08Hz）功率谱与整个频率范围功率谱的比值，并在两组静息态fMRI数据中对该方法进行了测试。结果显示，默认模式网络内的脑区，包括后扣带回皮质、楔前叶、内侧前额叶皮质和双侧下顶叶小叶，其fALFF显著高于其他脑区。这种模式与先前的神经影像学结果一致。静息态fMRI中脑池区域的非特异性信号成分被显著抑制，表明fALFF方法提高了检测自发脑活动的敏感性和特异性。其机制以及对异常脑活动的敏感性应在未来的研究中进行评估。
