The finding comes from a method of visualising brain connections, although it doesn't give an idea of how the differences initially arose.
Ragini Verma at the University of Pennsylvania, Philadelphia, and her colleagues scanned the brains of 949 males and females between the ages of 8 and 22. They focused on two regions: the cortex, involved in thought, perception and language; and the cerebellum, which coordinates movement. Their method tracks the motion of water molecules to show where nerves stop and start, revealing what is known as the connectome.
The left and right hemispheres of the cortex were much more connected with each other in females than males. But in males, each cerebellum had more links to the cortex on the opposite side of the brain than females. This favours connections that promote coordinated movement – something males generally do faster in tests.
The cortical link-up in females would promote communication between areas involved in analytical and verbal tasks and those for spatial and intuitive processing, the team says. Among other things, this could reflect a superior ability to process emotions and understand others' intentions.
The way the findings have been analysed so far, says Verma, shows how males and females as a whole differ. "We identified differences that survive rigorous mathematical and statistical analysis in a population."
Now, they want to find out whether individual male and female brains within those populations always differ along these lines, or whether there is a range of variations in which the sexes overlap. This should also show which networks men and women always share, and whether any are always sex-specific.
The same set of data includes measurements that reveal nerve function, so another goal is to see whether that follows the same pattern as the neural connections, says Verma. "As in any highway network, so in the brain: the roads, shown by the structural connectivity, and the traffic, shown by the functional connectivity, should jointly form a complete picture."
MacKenzie, Debora. 2014. “Mapped: male and female brain connections”. New Scientist. Posted: December 3, 2013. Available online: http://www.newscientist.com/article/dn24686-mapped-male-and-female-brain-connections.html#.Up34--LMqJI