Scientists Find Differences in Mammalian Male and Female Brains

Scientists have found difference in mammalian males and females based on a study done in mice. There are some cells unique to male brain and some unique to female brain. These sex-specific cells were found in a regioin of the brain that governs both aggression and mating behaviours. 
The findings were reported in the online version of the journal Cell recently and David Anderson of Howard Hughes Medical Institute involved in the study said that there are differences between male and femala mammalian brains at the level of cellular composition as well as gene expression but those differences are subtle, and their functional significance remains to be explained. 
There are many different types of cells within the brain, such as neurons that transmit signals and glial cells that support neural functions. Although all of these cells contain the same set of genes, or genome, the types of cells differ in how they express those genes. As an analogy, one can imagine the genome as an 88-key piano in each cell. Each cell does not use all 88 keys. Therefore, the subset of keys that the cell "plays" determines the type of cell it is. 
The hypothalamus is a fundamental region of the brain found in all vertebrates including humans. Previous studies have shown that a specific anatomic subdivision in the hypothalamus, called the ventrolateral subdivision of the ventromedial hypothalamus (VMHvl), contains cells that control aggression and mating behaviors. In these studies, strong stimulation of these neurons in male and female mice immediately caused the animals to become aggressive, even in the absence of any threat. However, weak stimulation caused the mice to begin mating behaviors. 
It was known that different genes are expressed in the two mouse sexes—indeed, a genetic test can tell you whether a mouse is male or female—but this is the first discovery of types of cells that are sex-specific in a mammalian brain. Cells are considered to be distinct types when the expression of large clusters of genes varies from cell to cell. 
Future work will try to determine the functions of these differing cell types.

Source : Caltech