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

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

doi:10.3389/fnins.2021.748080

Abstract

AimNeuroimaging 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.MethodsWe 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.ResultsThe 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.ConclusionThese 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.

Highlights

Gender differences in behavioral and cognitive domains have been reported by extensive studies (Miller and Halpern, 2014)
Compared with PA imaging, we found that AP imaging exhibited greater local spontaneous brain activity (i.e., amplitude of low frequency fluctuations (ALFF), fractional ALFF (fALFF), and regional homogeneity (ReHo)) in the anterior cingulate cortex, medial frontal cortex, superior frontal gyrus, middle frontal gyrus (MFG), inferior orbitofrontal gyrus, putamen, caudate, insula, inferior parietal lobule, superior parietal lobule, and parahippocampal gyrus, but showed weaker local spontaneous brain activity in the medial orbitofrontal cortex, inferior frontal gyrus, parts of caudate and putamen, precentral gyrus, middle temporal gyrus (TG), and cerebellum (Figure 2)
As to the resting-state functional connectivity (rsFC) of posterior cingulate cortex (PCC), AP imaging exhibited greater rsFCs in the anterior cingulate cortex, medial frontal cortex, superior frontal gyrus, and inferior TG, but weaker rsFCs in the caudate and cerebellum when compared with PA imaging

Summary

Introduction

Gender differences in behavioral and cognitive domains have been reported by extensive studies (Miller and Halpern, 2014). Reports of gender differences have spurred interest in investigating structural and functional brain features, which may underlie previous findings of cognitive and behavioral differences. Males tended to exhibit more intrahemispheric connectivity, whereas females appeared to exhibit more interhemispheric connectivity (Ingalhalikar et al, 2014). Apart from these anatomical differences, many studies have reported gender differences in brain functions by utilizing cognitive tasks (Shaywitz et al, 1995; Canli et al, 2002), which showed that male and female brains might have some different neural mechanisms. Researches into the neurobiology of gender differences may provide insights into the risk and protective factors associated with psychopathology (Cahill, 2006)

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