A new study from Indiana University provides evidence in mice that males may play a positive role in the development of offspring's brains starting before pregnancy. The research, reported June 30 in the Proceedings of the Royal Society of London B: Biological Sciences, found that female mice exposed to male pheromones gave birth to infants with greater mental ability.

"This is the first study to show that pheromone exposure exerts an influence across generations in mammals," said Sachiko Koyama, an associate research scientist at the IU Bloomington Medical Sciences Program and visiting scientist at the IU College of Arts and Sciences' Department of Psychological and Brain Sciences, who led the study.

"We found that male pheromones seem to influence the nutritional environment following birth, resulting in changes to the brain that could extend to future generations," she added.

Pheromones are chemical signals used to communicate between organisms of the same species. The connection between male pheromones and offspring's brain development seems to stem from the influence of male pheromones on the nursing ability of mother mice.

Specifically, IU scientists measured greater mammary gland development in mice exposed to male pheromones a week after exposure, which may have led to greater volumes or improved quality of milk production. These mother mice also showed lengthier nursing periods compared to mice not exposed to the male pheromone.

To measure the intelligence of the offspring, IU scientists placed mice in a water maze with a hidden platform. The mice born of mothers exposed to male pheromones learned the location of the hidden platform much faster, suggesting quicker learning and stronger spatial memory compared to the control group.

These improvements in brain development and cognitive function may stem from specific "neuro-enhancing" chemicals in breast milk, such as sialic acid, a component of breast milk also found at high levels in the brain during early development. IU researchers found higher levels of polysialyltransferase -- an enzyme that requires sialic acid to produce a molecule involved in neural cell development -- in the brains of the offspring of female mice exposed to male pheromones compared to the control group.