What causes behavioural differences in males, females

US researchers have discovered a mechanism for how androgens -- male sex steroids -- sculpt brain development, which could ultimately help understand development of social behavioural differences between males and females.

The team, from the University of Maryland in the US, discovered a mechanism for how androgens sculpt the brains of male rats to produce behavioural differences, such as more aggression and rougher play behaviour.

"We already knew that the brains of males and females are different and that testosterone produced during the second trimester in humans and late gestation in rodents contributes to the differences but we did not know how testosterone has these effects," said Margaret M. McCarthy from the varsity.

The study, published in Neuron journal, revealed that the number of newborn cells in the part of the brain called the amygdala, which controls emotions and social behaviours acts as a key contributor to the differences in behaviour between males and females.

Males have fewer of these newborn cells, because they are actively eliminated by immune cells by endocannabinoids which plays a role in reproductive functions and response to stress.

Female rats were, however, found to be unaffected. Moreover, in females, the newborn cells differentiated into a type of glial cell, the most abundant type of cell in the central nervous system.

"These discoveries into brain development are critical as we work to tackle brain disorders as early in life as possible, even in pregnancy," said E. Albert Reece, Professor at the varsity's School of Medicine.