A week or so ago earthsky.org, a favorite source for science news, reported on a study using a relatively new technology that mapped neural connectivity in the brains of 949 youth aged 8-22. They found gender differences that appeared in adolescence and were most pronounced in the young adults. Males had greater connectivity within each cerebral hemisphere and females had greater connectivity between the two hemispheres. The investigators interpreted this as supporting other findings which show that males do better at specific tasks depending on spatial and motor skills and females do better at memory and social cognition.
How do such differences arise? That they appear later in development suggests that experience and practice play an important role, but we know that gender differences arise early on in our development. Mammalian (yes, that includes us) fetuses are essentially female and some are masculinized in the course of gestation through the operation of hormones such testosterone. Bird brains are the opposite, they are essentially masculine but are feminized by hormones. Testosterone affects the developmental pace of the two cerebral hemispheres differently,slowing down the maturation of the left relative to the right. Because males produce more testosterone their hemispheres differ more than those of females. Some research shows that the cortical layering needed for accurate processing can be disrupted in the left hemisphere with the result that males are at greater risk for language disorders.
The greater social abilities of females come in part from the greater integration between the right hemisphere, which leads in processing the current moment and empathic communication, and the left, which leads in processing information displaced in time/space, i.e., abstract, and skilled motor actions, i.e., praxis. Males’ greater abilities in spatial abstraction for navigation and sensorimotor speed come in part from their focus on such mental domains set apart from the current social moments.
Jaak Panksepp in his book Affective Neuroscience says that there are really four sexes based on the different sexualization between body and brain. We can have a female body and brain, a male body and brain, and also a female body with a male brain and a male body with a female brain. It would be interesting to know if these differences in connectivity appear similarly in the LGBT populations.
Here is link to the story: