Researchers at the University of Pennsylvania have found striking differences in how men's and women's brains are wired. In one brain region, women have more connections between left and right hemispheres, and men within hemispheres, while in another brain region, it is the other way around.
Researchers say the differences may explain, for example, why on average men are better at learning and performing single tasks, such as cycling or navigating, while women tend to be better at multitasking and problem-solving in group situations.
The study is one of the largest to compare the "connectomes" - comprehensive maps of neural connections in the brain - of male and female humans.
The team describes the findings in a recent online issue of the Proceedings of the National Academy of Sciences (PNAS).
Brain wiring different and complementary
Researchers found increased connectivity in males from front to back within one hemisphere (upper) and left to right in females (lower).
Credit: Ragini Verma, PhD, Proceedings of National Academy of Sciences
Senior author Ragini Verma, associate professor in Penn's Perelman School of Medicine's department of Radiology, says:
"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."
Comparing brain maps during the course of development of nearly 1,000 young people aged between 8 and 22 years, the team found that females had greater connectivity between left and right hemispheres in the supratentorial region - which contains the largest part of the brain, the cerebrum.
On the other hand, males showed greater connectivity within each hemisphere.
But in the cerebellum - a brain region important for motor control - males had greater connectivity between the left and right hemispheres, while females showed more connectivity within each hemisphere.
The researchers suggest the differences in male and female connectomes likely give men a more efficient system for coordinated action where the cerebellum and cortex help bridge between perceptual experiences in the back of the brain.
In contrast, the female brain is likely better at integrating analytical and sequential processes of the left hemisphere with the processing of spatial, intuitive information that goes on the right hemisphere.
Co-author Ruben C. Gur, professor of psychology in Penn's department of Psychiatry, says:
"It's quite striking how complementary the brains of women and men really are."
Detailed maps of connectome made
Previous studies have shown brain differences between the sexes, but not to the extent of highlighting differences in neural wiring, and not in such a large population, say the researchers.
For their study, Profs. Verma, Gur and colleagues used a highly sensitive form of magnetic resonance imaging (MRI) known as diffusion tensor imaging (DTI), which tracks water travelling along nerve fibers. Highlighting these water tracks produces a detailed map of the pathways connecting different regions of the brain.
Gender differences in brain connectivity were more pronounced in participants over 13 years of age.
This imaging study is part of a larger behavior study being carried out at Penn. That study has shown stark behavior differences between the sexes, especially around the age of 13, with females outperforming males in tests of word and face memory, attention, and social cognition, and males doing better in tests of spatial processing and sensorimotor speed.
Prof. Gur says:
"Detailed connectome maps of the brain will not only help us better understand the differences between how men and women think, but it will also give us more insight into the roots of neuropsychiatric disorders, which are often sex related."
The team now plans to see if functional magnetic resonance imaging (fMRI) studies support these findings. And they also want to quantify how an individual's brain connectome differs from the general population, as well as find out more about which connections are different and which are the same between the sexes.
Funds from the National Institutes of Mental Health helped finance the study.
In another study published in the open access journal Biology of Sex Differences in September 2012, researchers found that men and women see things differently because their brains' visual centers work differently - they suggested while women are better at distinguishing colors, men are more sensitive to fine detail and rapidly moving stimuli.