Motherhood is good for the brain, US scientists conclude

MOTHERHOOD HAS a beneficial effect on learning and memory, because having children is - contrary to perceived wisdom - an exercise in intellectual stimulation.

Scientists have found evidence to suggest that being a mother results in the brain being literally reshaped to help it to solve problems associated with having offspring. The study behind those conclusions was carried out on rats, but the researchers believe the findings may apply to all mammals, including humans, because of the fundamental similarity in the way female hormones affect the brain in different species.

Craig Kinsley, a psychologist from the University of Richmond, in Virginia, led a research team that found mother rats to be significantly cleverer than virgin females. "There is enough similarity between rats and humans in terms of the way hormones affect the brain to merit some speculation," Dr Kinsley said.

Experiments on two different strains of rats, reported in the journal Nature, showed that the ability of maternal rats to be better at using their brains was not the result of genetic differences and so was likely to be due to motherhood.

The first experiment showed that mothers were better at making the right choices when given simple options; a second experiment showed they were about three times faster at extricating themselves from a maze. Dr Kinsley and his colleagues believe the difference between mothers and virgins is due to the raised levels of the female hormones oestradiol and progesterone, which are known to affect the brain. It was already known that raised levels of the two hormones during the oestrus cycle of mammals increase the concentration of dendritic spines, the protuberances at the ends of nerve cells that improve the connection at the junctions, or synapses, of brain cells.

"Pregnancy," the scientists say, "may produce long-lived improvements in behaviours that are not maternal as such, but which contribute to the survival and rearing of pups."

The hormones mainly affect cells in the hippocampus of the brain, which is involved in creating and retaining memories - a key part of learning. Having children exposes a female's brain to "rich sensory events" - new sights, sounds, smells and tactile stimulation, such as suckling.

When it comes to mothers and babies, intellectual development is a two- way process.