Sex differences in the structural connectome of the human brain

Abstract

Sex differences in human behavior show adaptive complementarity: Males have better motor and spatial abilities, whereas females have superior memory and social cognition skills. Studies also show sex differences in human brains but do not explain this complementarity. In this work, we modeled the structural connectome using diffusion tensor imaging in a sample of 949 youths (aged 8-22 y, 428 males and 521 females) and discovered unique sex differences in brain connectivity during the course of development. Connection-wise statistical analysis, as well as analysis of regional and global network measures, presented a comprehensive description of network characteristics. In all supratentorial regions, males had greater within-hemispheric connectivity, as well as enhanced modularity and transitivity, whereas between-hemispheric connectivity and cross-module participation predominated in females. However, this effect was reversed in the cerebellar connections. Analysis of these changes developmentally demonstrated differences in trajectory between males and females mainly in adolescence and in adulthood. Overall, the results suggest that male brains are structured to facilitate connectivity between perception and coordinated action, whereas female brains are designed to facilitate communication between analytical and intuitive processing modes.

Keywords: diffusion imaging; gender differences.

Fig. 1.

Schematic of the pipeline for creating the SC.

Fig. 2.

Connection-wise analysis. (A) Brain networks show increased connectivity in males (Upper) and females (Lower). Analysis on the child (B), adolescent (C), and young adult (D) groups is shown. Intrahemispheric connections are shown in blue, and interhemispheric connections are shown in orange. The depicted edges are those that survived permutation testing at P = 0.05. Node color representations are as follows: light blue, frontal; cyan, temporal; green, parietal; red, occipital; white, subcortical. GM, gray matter.

Fig. 3.

Representative regions of the brain that have a higher PC at a significance level of P < 0.001. The regions have been projected onto the surface of the brain for better visualization. Red indicates a higher PC in the females, and blue indicates a higher PC in males (mainly localized to the cerebellum). Representative regions and their corresponding T values are shown in the figures. The other regions that show significant differences (with their respective T values; negative values indicate females > males) are listed in Table 3. These tests revealed that although multiple regions have higher PCs in females, the cerebellum has a higher PC in males. L, left; R, right.