m.r.i. scans show how hormones change our brains. harmonise exercise a continual influence time before birth they have a strong impact on how our brain develops but they also affect us our whole life long and that s particularly apparent with women during the course of their menstrual cycle. estrogen increases over the course of the menstrual cycle and progesterone also starts to kick in a bit later. studies of the effect of estrogen have revealed that when levels are low women s behavior tends to resemble men s behavior more closely and that was found on men in the house and that means when a woman is having her period her brain is more under the influence of testosterone than on the other days of her cycle so it isn t as straightforward as one might think. in recent years research has focused