IT MIGHT seem unlikely, but the mood swings many women experience every month may serve an evolutionary purpose - to get them pregnant.
Levels of sex hormones such as oestrogen and progesterone fluctuate throughout the monthly cycle. During the follicular phase at the start of the cycle, the egg is maturing and the body releases oestrogen, while during the luteal phase, when a fertilised egg might implant, progesterone is secreted.
To see how these might influence the brain, Jean-Claude Dreher and colleagues at the National Institute of Mental Health in Bethesda, Maryland, used functional MRI to look at how brain activity changes over the course of the month.
The team scanned the brains of 15 women at different stages in their menstrual cycle as they played a game with hypothetical prizes of money. During the follicular phase, the orbitofrontal cortex, an area of the brain associated with decision making and ...