Centre for Functional MRI of the Brain (FMRIB), Wellcome Centre for Integrative Neuroimaging, Nuffield Department of Clinical Neurosciences, University of Oxford, UK.
Centre for Functional MRI of the Brain (FMRIB), Wellcome Centre for Integrative Neuroimaging, Nuffield Department of Clinical Neurosciences, University of Oxford, UK.
Neuroimage. 2017 Oct 1;159:57-69. doi: 10.1016/j.neuroimage.2017.07.014. Epub 2017 Jul 13.
The amplitudes of spontaneous fluctuations in brain activity may be a significant source of within-subject and between-subject variability, and this variability is likely to be carried through into functional connectivity (FC) estimates (whether directly or indirectly). Therefore, improving our understanding of amplitude fluctuations over the course of a resting state scan and variation in amplitude across individuals is of great relevance to the interpretation of FC findings. We investigate resting state amplitudes in two large-scale studies (HCP and UK Biobank), with the aim of determining between-subject and within-subject variability. Between-subject clustering distinguished between two groups of brain networks whose amplitude variation across subjects were highly correlated with each other, revealing a clear distinction between primary sensory and motor regions ('primary sensory/motor cluster') and cognitive networks. Within subjects, all networks in the primary sensory/motor cluster showed a consistent increase in amplitudes from the start to the end of the scan. In addition to the strong increases in primary sensory/motor amplitude, a large number of changes in FC were found when comparing the two scans acquired on the same day (HCP data). Additive signal change analysis confirmed that all of the observed FC changes could be fully explained by changes in amplitude. Between-subject correlations in UK Biobank data showed a negative correlation between primary sensory/motor amplitude and average sleep duration, suggesting a role of arousal. Our findings additionally reveal complex relationships between amplitude and head motion. These results suggest that network amplitude is a source of significant variability both across subjects, and within subjects on a within-session timescale. Future rfMRI studies may benefit from obtaining arousal-related (self report) measures, and may wish to consider the influence of amplitude changes on measures of (dynamic) functional connectivity.
大脑活动自发波动的幅度可能是个体内和个体间变异性的重要来源，这种变异性很可能会传递到功能连接（FC）估计中（无论是直接还是间接）。因此，更好地理解静息态扫描过程中幅度的波动以及个体间幅度的变化，对于解释 FC 研究结果具有重要意义。我们在两项大规模研究（HCP 和 UK Biobank）中研究了静息态幅度，旨在确定个体间和个体内的变异性。个体间聚类将大脑网络分为两组，两组之间的幅度变化在个体之间高度相关，这揭示了初级感觉和运动区域（“初级感觉/运动聚类”）与认知网络之间的明显区别。在个体内，初级感觉/运动聚类中的所有网络在扫描开始到结束时都表现出幅度的一致增加。除了初级感觉/运动幅度的强烈增加外，在比较同一天采集的两次扫描时（HCP 数据），还发现了大量的 FC 变化。附加信号变化分析证实，所有观察到的 FC 变化都可以完全用幅度变化来解释。在 UK Biobank 数据中，个体间的相关性显示，初级感觉/运动幅度与平均睡眠时间之间呈负相关，这表明唤醒状态起到了一定的作用。我们的研究结果还揭示了幅度与头部运动之间的复杂关系。这些结果表明，网络幅度是个体间以及个体内（在单次会话的时间尺度上）变异性的重要来源。未来的射频磁共振成像研究可能受益于获得与唤醒相关的（自我报告）测量值，并可能希望考虑幅度变化对（动态）功能连接测量值的影响。
