Wang Yun, Chen Xiongying, Liu Rui, Zhang Zhifang, Zhou Jingjing, Feng Yuan, Jiang Chao, Zuo Xi-Nian, Zhou Yuan, Wang Gang
Beijing Key Laboratory of Mental Disorders, National Clinical Research Center for Mental Disorders, Beijing Anding Hospital, Beijing, China.
Advanced Innovation Center for Human Brain Protection, Capital Medical University, Beijing, China.
Front Neurosci. 2022 Jan 25;15:748080. doi: 10.3389/fnins.2021.748080. eCollection 2021.
Neuroimaging studies have highlighted gender differences in brain functions, but conclusions are not well established. Few studies paid attention to the influence of phase-encoding (PE) direction in echo-planar imaging on gender differences, which is a commonly used technique in functional magnetic resonance imaging (fMRI). A disadvantage of echo-planar images is the geometrical distortion and signal loss due to large susceptibility effects along the PE direction. The present research aimed to clarify how PE direction can affect the outcome of a specific research on gender differences.
We collected resting-state fMRI using anterior to posterior (AP) and posterior to anterior (PA) directions from 113 healthy participants. We calculated several commonly used indices for spontaneous brain activity including amplitude of low frequency fluctuations (ALFF), fractional ALFF (fALFF), regional homogeneity (ReHo), degree centrality (DC), and functional connectivity (FC) of posterior cingulate cortex for each session, and performed three group comparisons: (i) AP versus PA; (ii) male versus female; (iii) interaction between gender and PE direction.
The estimated indices differed substantially between the two PE directions, and the regions that exhibited differences were roughly similar for all the indices. In addition, we found that multiple brain regions showed gender differences in these estimated indices. Further, we observed an interaction effect between gender and PE direction in the bilateral middle frontal gyrus, right precentral gyrus, right postcentral gyrus, right lingual gyrus, and bilateral cerebellum posterior lobe.
These apparent findings revealed that PE direction can partially influence gender differences in spontaneous brain activity of resting-state fMRI. Therefore, future studies should document the adopted PE direction and appropriate selection of PE direction will be important in future resting-state fMRI studies.
神经影像学研究突出了大脑功能的性别差异，但结论尚未完全确立。很少有研究关注回波平面成像中相位编码（PE）方向对性别差异的影响，而回波平面成像在功能磁共振成像（fMRI）中是一种常用技术。回波平面图像的一个缺点是由于沿PE方向的大磁化率效应导致几何失真和信号损失。本研究旨在阐明PE方向如何影响关于性别差异的特定研究结果。
我们从113名健康参与者那里收集了从前到后（AP）和从后到前（PA）方向的静息态功能磁共振成像数据。我们为每个时段计算了几个常用的自发脑活动指标，包括低频波动幅度（ALFF）、分数ALFF（fALFF）、局部一致性（ReHo）、度中心性（DC）以及后扣带回皮质的功能连接（FC），并进行了三组比较：（i）AP与PA；（ii）男性与女性；（iii）性别与PE方向之间的相互作用。
两个PE方向之间估计的指标存在显著差异，并且所有指标显示出差异的区域大致相似。此外，我们发现多个脑区在这些估计指标上存在性别差异。进一步地，我们在双侧额中回、右侧中央前回、右侧中央后回、右侧舌回以及双侧小脑后叶观察到性别与PE方向之间的相互作用效应。
这些明显的发现表明，PE方向可部分影响静息态功能磁共振成像中自发脑活动的性别差异。因此，未来的研究应记录所采用的PE方向，并且在未来的静息态功能磁共振成像研究中适当选择PE方向将很重要。
