Another Part of the Puzzle

From the University of Uppsala :

Sex-based prenatal brain differences found

Prenatal sex-based biological differences extend to genetic expression in cerebral cortices. The differences in question are probably associated with later divergences in how our brains develop. This is shown by a new study by Uppsala University researchers Elena Jazin and Björn Reinius, which has been published in the latest issue of the journal Molecular Psychiatry.

Professor Elena Jazin and doctoral student Björn Reinius at the Department of Physiology and Developmental Biology previously demonstrated that genetic expression in the cerebral cortices of human beings and other primates exhibits certain sex-based differences. It is presumed that these differences are very old and have survived the evolutionary process. The purpose of the new study was to determine whether they appear during the process of brain development or first upon the conclusion of that process. Identifying the initial genetic mechanisms that prompt the brain to develop in a female or male direction is a long-range research objective.

The Uppsala University researchers analysed data, on the basis of sex, from another extensive study of the prenatal human brain.

"The results show that many of the genes situated on the Y chromosome are expressed in various parts of the brain prior to birth and probably provide a developmental basis for the sex-based differences exhibited by adult brains," according to Elena Jazin.

More than a third of Y-chromosomal genes appear to be involved in sex-based human brain differentiation. Some of the genetic activity in question is evident in the adult brain, while other of it only appears at earlier stages of brain development. It is yet unknown whether the differences in genetic expression among female and male brains have any functional significance.

"The findings are consistent with other factors, such as environment, also playing a role in how we develop," emphasizes Elena Jazin.

Knowledge of the development of sex-based brain differences is of potential significance for the treatment of brain disturbances and diseases. A large number of psychiatric illnesses, including depression and autism, affect men and women differentially.

"Taking account of sex-based differences is crucial to the study of normal and abnormal brain activity," according to Elena Jazin.

One of the mysteries we haven't yet solved is why trans women's brains develop differently in adulthood from those of males. Some of the differences between males and female brains - like the infamous BSTc layer in the hypothalamus that is cross-gendered in trans people - only develop the difference in adulthood. Yet transsexuality is obvious long before then, in the vast majority of cases. The neurological differences that appear only in adulthood are symptomatic, not causal. This research might help us understand why, if only by showing areas of sexual differentiation that are not contingent on the presence of a Y-chromosome. What is the mechanism of such neurological predestination?

The penny is starting to drop, even in the popular press. From the UK Daily Mail:

There are a number of structural and functional differences between male and female brains.

The human brain is divided into two hemispheres that do different things. They are connected by the corpus callosum, a thick band of nerve tissue that carries information between the two.

This band of nerves is slightly larger, on average, in women than in men - which means the emotional right side of the brain is better connected to the analytical left side.

This may be why women are more emotionally aware. It may also allow emotion to be incorporated more readily into thought and speech.

When doing complex tasks, women use both sides of their brain, while men use the side more obviously suited to the task.

Over-simplified, dumbed down, but essentially correct - and you don't have to be a neuroscientist to grasp the essentials.