An intriguing communication from a group of psychologists in Virginia, published in Nature for November 11, reports that neural activity was enhanced in female rats during pregnancy and the rearing of offspring.
Motherhood involves a need to find and remember the location of food, water and warmth, so that these encouragements to survive and flourish may be exploited for the benefit of the rising generation. Pregnancy in mammals raises the levels of the steroid hormones oestradiol and progesterone circulating in the blood.
The effect of this is to increase the concentration of apical dendritic spines in the hippocampus of the brain. The resultant increase in neural activity may physically reshape the brain area affected and increase the ability of the animal to deal with a more demanding environmental challenge. Moreover, the hypothalamic connections are reorganised by the novel stimuli of sights, sounds, odours, tastes and touch which accompany the arrival of a newborn litter. Altogether, the powers of learning and memory are materially enhanced in the mother, who can then cope with the task of ensuring the survival and thriving of her offspring.