Effect of Phase-Encoding Direction on Gender Differences: A Resting-State Functional Magnetic Resonance Imaging Study

Yun Wang; Xiongying Chen; Rui Liu; Zhifang Zhang; Jingjing Zhou; Yuan Feng; Chao Jiang; Xi-Nian Zuo; Yuan Zhou; Gang Wang

doi:10.3389/fnins.2021.748080

Effect of Phase-Encoding Direction on Gender Differences: A Resting-State Functional Magnetic Resonance Imaging Study

Front Neurosci. 2022 Jan 25:15:748080. doi: 10.3389/fnins.2021.748080. eCollection 2021.

Authors

Yun Wang¹, Xiongying Chen¹, Rui Liu¹, Zhifang Zhang¹, Jingjing Zhou¹, Yuan Feng^{1

2}, Chao Jiang³, Xi-Nian Zuo⁴, Yuan Zhou^{1

5

6}, Gang Wang^{1

2}

Affiliations

¹ Beijing Key Laboratory of Mental Disorders, National Clinical Research Center for Mental Disorders, Beijing Anding Hospital, Beijing, China.
² Advanced Innovation Center for Human Brain Protection, Capital Medical University, Beijing, China.
³ Beijing Key Laboratory of Learning and Cognition, School of Psychology, Capital Normal University, Beijing, China.
⁴ State Key Laboratory of Cognitive Neuroscience and Learning, Beijing Normal University, Beijing, China.
⁵ CAS Key Laboratory of Behavioral Science, Institute of Psychology, Beijing, China.
⁶ Department of Psychology, University of Chinese Academy of Sciences, Beijing, China.

Abstract

Aim: 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.

Methods: 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.

Results: 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.

Conclusion: 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.

Keywords: functional connectivity; functional magnetic resonance imaging; gender difference; phase-encoding direction; spontaneous brain activity.