December 13, 2013

Sex Differences Show Up in The Brain's Networks

Men and women are literally polar opposites. Brain scans reveal us why women are better at meetings, and men, at maps.

This much people agree on: Men and women are different. Even if they are not so far apart as Mars and Venus, research has found that men and women generally approach romantic relationships with differing expectations and seem to consistently show different cognitive styles and mental strengths.

Using a new form of brain imaging, researchers at the University of Pennsylvania Perelman School of Medicine looked at how different regions are connected across the brain as a whole. They found that men and women really are polar opposites, at least in terms of their brains' connectivity.

Females outperformed males on tests of attention, memory and social cognition. Males outperformed females on tests of spatial processing and sensorimotor speed.

Men had greater connectivity from front to back in each of the brain's two hemispheres; women had greater connectivity across the left and right hemispheres. The results suggest that these differences in neural wiring between men and women have an impact on gender-specific behaviors.

Using a water-based imaging technique called diffusion tensor imaging (DTI), scientists viewed the connections in the brains of nearly a thousand people aged 8 to 22 years. DTI can trace and highlight the individual neural fibers connecting the different regions of the brain, providing a “connectome,” a comprehensive map of the complex neural networks of the brain at a higher resolution than ever before.

The stronger left-to-right connectivity across both hemispheres seen in women suggested there was better communication between their analytical processes and intuition. This may help explain why women have better memory and social cognition skills, making them more equipped for multitasking and working with a group.

Similarly, men, with their greater front-to-back connectivity, appear wired to coordinate perception with coordinated action, an ability that helps explain why men are often better than women at learning and understanding spatial tasks like navigating a set of directions.

These findings were supported by the results from a study of behavior given to the same group of participants. Females outperformed males on tests of attention, memory and social cognition. Males outperformed females on tests of spatial processing and sensorimotor speed.

Overall, the authors concluded that the results from the behavior tests agreed with the sex differences found in the structural study. In children younger than 13 years, they noted only a few gender differences for connectivity, but in adolescents aged 14 to 17 years and young adults older than 17 the differences were more pronounced, suggesting sex hormones likely play a role.

“These maps show us a stark difference — and complementarity — in the architecture of the human brain that helps provide a potential neural basis as to why men excel at certain tasks, and women at others,” Dr. Ragini Verma, one of the authors, said in a statement.

In the future, the scientists want to use functional magnetic resonance imaging (fMRI) to see whether activity in different brain regions is gender-specific as men and women undergo certain behavioral tasks.

This study was published in December in the journal Proceedings of the National Academy of Sciences.

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