Academic Radiology, University of Nottingham, Queen's Medical Centre, Nottingham, NG7 2UH, UK,
MAGMA. 2010 Dec;23(5-6):367-74. doi: 10.1007/s10334-010-0199-6. Epub 2010 Feb 19.
Increases in low-frequency fluctuations (LFF, 0.01-0.1 Hz) of BOLD fMRI signal were observed during sedation and sleep. We tested the hypothesis that sedation-induced LFF increases may be mediated by increased head motion likely associated with these brain states.
Twenty healthy volunteers were scanned in resting-state baseline and (15 thereof) in midazolam sedation condition. After standard preprocessing, LFF power was computed from average time series from 14 ROIs representing 5 functional networks (visual, motor, auditory, default mode, dorsal attentional). We assessed the effects of sedation on LFF and indirect effects of head motion (mean relative displacement) using mediation analysis.
Sedation increased LFF power with the indirect effect of motion on sedation-induced LFF significant for all networks. Global mean corrected data showed similar but weaker results: significant total effect for auditory, motor and visual; significant mediation for auditory and motor networks. Motion was strongly correlated with LFF even at baseline. Reported results were significant at p < 0.05.
The study confirms that conscious sedation induces LFF increase, but demonstrates that this effect is mediated by increased head motion. Hence, caution in design and interpretation is recommended for studies comparing subjects or conditions differently predisposing to head motion.
在镇静和睡眠期间观察到 BOLD fMRI 信号低频波动（LFF，0.01-0.1 Hz）增加。我们检验了以下假设，即镇静诱导的 LFF 增加可能是由与这些脑状态相关的头部运动增加介导的。
20 名健康志愿者在静息状态基线和（其中 15 名）咪达唑仑镇静状态下进行扫描。在标准预处理后，从代表 5 个功能网络（视觉、运动、听觉、默认模式、背侧注意力）的 14 个 ROI 的平均时间序列中计算 LFF 功率。我们使用中介分析评估了镇静对 LFF 的影响以及头部运动（平均相对位移）的间接影响。
镇静增加了 LFF 功率，运动对镇静诱导的 LFF 的间接影响在所有网络中均具有统计学意义。全局平均校正数据显示出类似但较弱的结果：听觉、运动和视觉的总效应显著；听觉和运动网络的中介效应显著。即使在基线时，运动也与 LFF 强烈相关。报告的结果在 p < 0.05 时具有统计学意义。
该研究证实，意识镇静会引起 LFF 增加，但表明这种效应是由头部运动增加介导的。因此，对于比较不同头部运动倾向的受试者或条件的研究，建议在设计和解释时要谨慎。
