Effect of ovarian cycle on MEG gamma oscillations in healthy women

Previous invasive studies in mice and non-invasive EEG studies in humans suggest that parameters of gamma oscillations change with the stage of the ovarian cycle. This phenomenon is thought to reflect the impact of cyclic fluctuations of neurosteroid concentration on the regulation of neural excitation and inhibition in the brain. Tracking changes in MEG gamma oscillations may help to characterize changes of the excitation/inhibition balance during the normal menstrual cycle and distortions of this balance in cyclic disorders such as premenstrual syndrome (PMS), premenstrual dysphoric disorder (PMDD) and catamenial epilepsy. In this study we record visually induced MEG gamma oscillations in healthy women in two phases of the menstrual cycle that differ in concentration of neurosteroids. We expect that the ‘gamma-based’ measures of the excitation-inhibition balance described in our previous study will reflect the E/I balance fluctuations during the menstrual cycle.