How does the combined-oral contraceptive affect the electrophysiology of the human female brain?

It is well documented that the gonadal steroids, particularly oestradiol and progesterone, affect the major inhibitory and excitatory systems in the brain. As a result oestradiol and progesterone play a central role in major theories on the causes of menstrual cycle-linked neurological disorders such as pre-menstrual dysphoric disorder (episodes of major depression and physical symptoms beginning prior to menstruation), and catamenial epilepsy (a doubling of epileptic seizures at specific points of the menstrual cycle).

One of the major barriers to understanding menstrual cycle-linked neurological disorders has been an historical lack of sensitive measures of changes in hormone function in the human brain. Much of what we understand about the neural basis of menstrual cycle-related disorders relies on animal models, particularly rodents.

Our groups previous research on healthy human females combined simple visual stimulation with electroencephalography (EEG) recording and computational models of brain network communication over the menstrual cycle. These measures demonstrated remarkable sensitivity to the inhibitory and excitatory effects of gonadal steroids.

In New Zealand the combined oral contraceptive (COCP) is one of the most widely used forms of contraception. While the COCP suppresses oestradiol and progesterone fluctuations over the menstrual cycle, most COCPs offer no therapeutic benefit to menstrual cycle-linked disorders. Our research group want to understand why. This current project will contribute to growing knowledge on the effect of gonadal steroids on the female brain by investigating the impact of the COCP on EEG signal and visual psychophysics over the course of a month.

The outcomes will inform the design of a planned project that will investigate the pathophysiology of catamenial epilepsy.