Distinct sex differences in personality traits associated with brain regional gray matter volumes

Relationships between personality traits and brain regions have been widely studied, but not potential sex-based differences, despite sex hormones affecting neuronal activity and brain functions. We aimed to determine whether there are fundamental sex-related disparities in that relationship. We enrolled healthy university students (103 men, 111 women). Regional brain gray matter volumes were measured using voxel-based morphometry on T1-weighted brain MRI, and personality traits were assessed using the temperament and character inventory. Gray matter volumes (GMVs) in the right precentral cortex were inversely related with the persistence score (r = -0.36, FDR-corrected p  = 0.036) only for females. Distribution of the brain regions associated with each personality factor determined by TCI (uncorrected p  < 0.05, Pearson’s correlation) was different between the sexes. For instance, one factor such as harm avoidance for female was related mainly to the GMVs of the parietal, temporal and thalamic regions, whereas that for male was related mainly to the sensorimotor and cerebellar regions. Using these regions’ GMVs as predictors for each sex and personality factor, all the seven personality factors were predicted by general linear model analysis for females, whereas four factors were done for males. These findings suggest sex-specific neural bases underlying personality traits.