Correlations Between Personality and Brain Structure: A Crucial Role of Gender

Abstract

Previous studies have shown that males and females differ in personality and gender differences have also been reported in brain structure. However, effects of gender on this "personality-brain" relationship are yet unknown. We therefore investigated if the neural correlates of personality differ between males and females. Whole brain voxel-based morphometry was used to investigate the influence of gender on associations between NEO FFI personality traits and gray matter volume (GMV) in a matched sample of 182 males and 182 females. In order to assess associations independent of and dependent on gender, personality-GMV relationships were tested across the entire sample and separately for males and females. There were no significant correlations between any personality scale and GMV in the analyses across the entire sample. In contrast, significant associations with GMV were detected for neuroticism, extraversion, and conscientiousness only in males. Interestingly, GMV in left precuneus/parieto-occipital sulcus correlated with all 3 traits. Thus, our results indicate that brain structure-personality relationships are highly dependent on gender, which might be attributable to hormonal interplays or differences in brain organization between males and females. Our results thus provide possible neural substrates of personality-behavior relationships and underline the important role of gender in these associations.

Keywords: NEO-FFI; extreme personality disorders; hormonal influence; left precuneus/parieto-occipital sulcus; voxel brain morphometry.

Figure 1.

Distribution of siblings in the male and female sample with their relative zygosity (Not Twin, Dizygotic, Monozygotic). Groups’ abbreviations: m (males with no siblings); f (females with no siblings); m:m (males who have at least another male sibling); f:f (females with at least another female sibling); m:f (males with at least a female sibling); f:m (females with at least a male sibling); m:f+m (males with at least a male and a female sibling); f:m+f (females with at least a male and a female sibling).

Figure 2.

Mean scores of the 5 NEO FFI personality scales (neuroticism, extraversion, openness, conscientiousness, and agreeableness) separately for males (orange) and females (violet); error bars represent standard errors. Significant differences between males and females, marked by a star, were found for neuroticism and conscientiousness.

Figure 3.

Neural correlates of neuroticism in males. (A) Whole brain VBM results revealing negative relationships between neuroticism and GMV of POS/Cun, lFFG/Cb, and rFFG in males. (B) Correlations between neuroticism and GMV in POS/Cun, lFFG/Cb, and rFFG separately for males and females, with negative correlations in males but no correlation in females. (C) Functional decoding of the regions POS/Cun, lFFG/Cb, and rFFG; behavioral domains at P < 0.05 uncorrected for multiple comparison.

Figure 4.

Neural correlates of extraversion in males. (A) Whole brain VBM results revealing positive relationships between extraversion and GMV of Prc/POS, Th, lFFG/Cb, and rCb in males. (B) Correlations between extraversion and GMV in Prc/POS, Th, lFFG/Cb, and rCb separately for males and females, with positive correlations in males but no correlation in females. (C) Functional decoding of the regions Prc/POS, Th, lFFG/Cb, and rCb; behavioral domains at P < 0.05 uncorrected for multiple comparison.

Figure 5.

Neural correlates of conscientiousness in males. (A) Whole brain VBM results revealing positive relationships between conscientiousness and GMV of Prc/POS in males. (B) Correlations between extraversion and GMV in Prc/POS separately for males and females, with positive correlations in males but no correlation in females. (C) Functional decoding of the regions Prc/POS; behavioral domains at P < 0.05 uncorrected for multiple comparison.

Figure 6.

Three-way conjunction across the results of neuroticism, extraversion, and conscientiousness. (A) Results of the minimum conjunction analysis across the 3 traits revealing a cluster in lPrc/POS where GMV significantly correlated with all 3 personality scores in the male but not female sample. (B) Individual correlations between neuroticism, extraversion, and conscientiousness and GMV in lPrc/POS separately for males and females, with negative correlations in males but no correlation in females. (C) Behavioral characterization of lPrc/POS at P < 0.05, uncorrected for multiple comparison.

Figure 7.

Two-way conjunction across the results of neuroticism and extraversion. (A) Results of the minimum conjunction analysis between these 2 traits revealing bilateral POS/Cun, lFFG, and rCb. (B) Individual correlations between neuroticism and extraversion and GMV in POS/Cun, lFFG/Cb, and rCb separately for males and females, with negative correlations in males but no correlation in females. (C) Behavioral domains significantly associated with POS/Cun, lFFG/Cb, and rCb at P < 0.05 uncorrected for multiple comparison.