EEG changes during spontaneous and controlled menstrual cycles and their correlation with psychological performance

1. EEG (occipito-central, anterior and posterior temporo-central), blood concentration of hormones (oestradiol, progesterone, prolactin, folliculo-stimulating (FSH) and luteinizing (LH) hormones) and psychometric tests (reaction time, concentration, simple calculations, visual orientation and simple motor performance tasks) were recorded from 16 young women during a spontaneous menstrual cycle (s.c.w. group) and from 16 women taking combined oral contraceptives (o.c.w. group). All data were collected every second day except Sundays. 2. The EEGs underwent power spectrum analysis. Power and weighted mean frequency were determined for different frequency bands (theta, alpha and beta). The most constant finding in the s.c.w. group was a slight increase of mean alpha frequency during the luteal phase until menstruation (mean of occipital alpha acceleration = +0.3c/sec). The average time course of this acceleration fitted the time course of progesterone increase, but no direct correlation could be established. No such acceleration of alpha frequency could be found in the o.c.w. group, but the mean frequency in this group was about 0.5c/secslower than that of the s.c.w. group. In addition, minor cyclic changes of EEG paramenters in the s.c.w. group were observed in the occipital and temporal theta activity, the temporal alpha activity, but none in the beta range. 3. Reaction times to simple tasks, simple arithmetic, etc. were slightly but significantly decreased in the s.c.w. group during the luteal phase with a minimum on the day before or during menstruation. No such changes were observed in the o.c.w. group, which performed, in all tasks, slightly slower and slightly less correctly than the s.c.w. group. 4. The individual relative accelerations of alpha frequency and shortening of reaction times were positively correlated with each other.