Sex differences in brain gray and white matter in healthy young adults: Correlations with resting state ALFF

Objective: To study the differences of gray and white concentration and the amplitude of low-frequency fluctuation (ALFF) in resting-fMRI between male and female brains. Methods: Twenty male and twenty female graduate students underwent both anatomical MRI and resting-state fMRI scanning sessions. Voxel-based morphometry (VBM) was applied on structural magnetic resonance images and ALFF in the resting-fMRI was calculated. After data preprocessing, the relative concentration of gray and white matter and the ALFF in male and female brains were compared using a two-sample t-test. Results: Increased gray matter concentration in females versus males was observed in the superior parietal lobule, pre- and postcentral gyrus; Increased white matter concentration in females versus males was observed in the right genu of corpus callosum, superior parietal lobule and orbitofrontal cortex (OFC); And increased ALFF was observed in the right genu of corpus callosum, left medial and middle frontal gyrus, right posterior cingulate gyrus and subcallosal gyrus in female group compared to male group. Conclusions: The neural activities in prefrontal and posterior cingulate cortex within the default mode network (DMN) in women are stronger than in men; Sex difference in neural activity of right genu of corpus callosum is related to sex difference in volume of right genu of corpus callosum; Females have larger white matter concentration in right genu of corpus callosum and right OFC, which confirm prior reports of sex differences in OFC and corpus callosum structure.