UNASSIGNED:小动物fMRI是认知神经科学中转化研究的重要组成部分。由于尺寸小和动物生理学,临床前fMRI容易出现伪影,可能导致对数据的误解。为了得出无偏见的翻译结论,它是,因此,对于确定潜在的实验噪声来源以及开发无法避免的贡献(例如生理噪声)的校正方法至关重要。这项研究的目的是评估大鼠临床前fMRI中血液动力学振荡(HDO)的起源和患病率,以及它们对数据分析的影响。
UNASSIGNED:随着HDO检测和抑制算法的发展,对于不同的麻醉方案,研究了fMRI测量中的HDO患病率,包含异氟烷和美托咪定,以及梯度回波和自旋回波fMRI序列。除了评估血管舒张对HDO的影响,使用局部场电位(LFP)记录研究了HDO是否具有直接的神经元相关性。最后,评估了HDO对fMRI数据分析的影响,研究对激活图计算的影响以及对脑网络分析的影响。总的来说,在71只大鼠中进行了303次fMRI测量和32次LFP记录。
未经批准:总共,62%的fMRI测量显示HDO频率为(0.20±0.02)Hz。这种频繁发生表明在fMRI实验中通常不能忽略HDO。使用开发的算法,HDO检测的特异性为95%,并有效地从信号时间过程中删除。HDO在小血管和大血管的血管收缩条件下发生在整个大脑中。血管舒张立即中断HDO,which,然而,在血管收缩条件下1小时内返回。在LFP记录中未观察到HDO的直接神经元相关性。HDO显著影响功能磁共振成像数据的分析,导致激活体素的簇大小和F值发生变化,以及改变的大脑网络,比较有和没有HDO的数据时。
UNASSIGNED:因此,我们得出结论,HDO是在某些麻醉条件下由血管舒缩引起的,应在fMRI数据分析过程中进行校正,以避免偏倚。
UNASSIGNED: Small animal fMRI is an essential part of translational research in the cognitive neurosciences. Due to small dimensions and animal physiology preclinical fMRI is prone to artifacts that may lead to misinterpretation of the data. To reach unbiased translational conclusions, it is, therefore, crucial to identify potential sources of experimental noise and to develop correction methods for contributions that cannot be avoided such as physiological noise. Aim of this study was to assess origin and prevalence of hemodynamic oscillations (HDO) in preclinical fMRI in rat, as well as their impact on data analysis.
UNASSIGNED: Following the development of algorithms for HDO detection and suppression, HDO prevalence in fMRI measurements was investigated for different anesthetic regimens, comprising isoflurane and medetomidine, and for both gradient echo and spin echo fMRI sequences. In addition to assessing the effect of vasodilation on HDO, it was studied if HDO have a direct neuronal correlate using local field potential (LFP) recordings. Finally, the impact of HDO on analysis of fMRI data was assessed, studying both the impact on calculation of activation maps as well as the impact on brain network analysis. Overall, 303 fMRI measurements and 32 LFP recordings were performed in 71 rats.
UNASSIGNED: In total, 62% of the fMRI measurements showed HDO with a frequency of (0.20 ± 0.02) Hz. This frequent occurrence indicated that HDO cannot be generally neglected in fMRI experiments. Using the developed algorithms, HDO were detected with a specificity of 95%, and removed efficiently from the signal time courses. HDO occurred brain-wide under vasoconstrictive conditions in both small and large blood vessels. Vasodilation immediately interrupted HDO, which, however, returned within 1 h under vasoconstrictive conditions. No direct neuronal correlate of HDO was observed in LFP recordings. HDO significantly impacted analysis of fMRI data, leading to altered cluster sizes and F-values for activated voxels, as well as altered brain networks, when comparing data with and without HDO.
UNASSIGNED: We therefore conclude that HDO are caused by vasomotion under certain anesthetic conditions and should be corrected during fMRI data analysis to avoid bias.