EEG alpha indices depending on the menstrual cycle phase and salivary progesterone level

The effects of neurohumoral status on the EEG α activity were studied in 78 women (18–27 years old) during one or two menstrual cycles using a within-subjects design. The psychometric and electroencephalographic (EEG) indices of α waves, basal body temperature, and salivary progesterone level were monitored every two or three days. The menstrual and follicular recording sessions occurred before the basal temperature rise caused by ovulation, the luteal recording session occurred after the increase in progesterone level by more than 20% compared to the day before, and the premenstrual recording sessions occurred after the decrease in progesterone level by more than 20% compared to the day before. The EEG, electromyographic (EMG) and electrocardiographic (ECG) characteristics of cognitive efficiency and psycho-emotional tension were recorded at rest and during task performance. The experiments were started in the menstrual phase in half the subjects and in the luteal phase in the other half. Psychometric characteristics, EEG α activity, EMG and ECG indices were compared for all the five phases at rest and in response to cognitive task performance. The results have shown that all psychometric and α EEG indices are menstrual-cycle-dependent. The maximum cognitive fluency, α peak frequency, α band width, and power in the α2 frequency band are observed in the luteal phase, while the maximum power in the low-frequency α1 band, as well as visual and cognitive activation calculated from α power reduction, are observed in the follicular phase of the menstrual cycle. The hypothesis that EEG α activity depends on the neurohumoral status is supported by the positive correlation of salivary progesterone level with the α peak frequency and the power in the α2 band and its negative correlation with the power in the α1 band. It is concluded that psycho-physiological recording sessions in women must be carried out with due consideration of the menstrual cycle phase.