Sex differences between men and women's brain: from wiring to behavior?
(by Haohao Wu, 05/01/2014)

We all more or less have learnt the stereotypic idea that men are better at reading maps, while women have better social skills. And scientists keep addressing what is the biological basisthat makes "men are from Mars, women are from Venus". Recently, Dr. Ragini Verma and colleagues published their results which may answer this question, and this big finding also caused considerable controversy in the field.

In this study, the researchers used diffusion tensor imaging (DTI) to scan 949 brains from 428 males and 521 females aged 8 to 22.DTI maps the water diffusion in the brain tissue and therefore reveals the microscopic details of nerve fibers. With the advances in fiber tractography, the networks of the whole brain was analyzed and computed as a structural connectome (SC).

By this mean, the researchers discovered a striking difference between male and female brain networks: male brains showed more intra-hemispheric connections, while female brains showed more inter-hemispheric connections.This gender difference of brain network was not so significant in the children younger than 13, but started to show up in the adolescents between 14 and 17 and became pronounced in young adults older than 17.

Differences between male's and female's brain

Fig. 1: Brain networks show differences between males and females. Intra-hemispheric connections are shown in blue, and inter-hemispheric connections are shown in orange. Males have more front to back connections within one hemisphere, while females have more left to right connections across two hemispheres.
(Credit: RaginiVerma/PNAS)

The researchers of this study then wrote:

"The observations suggest that malebrains are structured to facilitate connectivity betweenperceptionand coordinated action, whereas female brains aredesigned to facilitate communication between analytical andintuitive processing modes."

The experimental result exactly matches how we think about our brains. However, the lack of evidence makes this interpretation not that convincing. Because this study has not made any link between the connectome result and behavior yet, it's probably too early to say that the different behaviors of males and females are due to different brain connections. Or there might be some other reasons for the finding of this study, e.g. we know that men's brains are generally larger than women's, and bigger brain is not as simple as smaller brain scales up. Further studies are still needed to finally explain why “men are from Mars, women are from Venus” or possibly "they are from the same planet".

The original paper:

Madhura Ingalhalikara et al. "Sex differences in the structural connectome of the human brain." PNAS (2013), doi: 10.1073/pnas.1316909110.