Reactivity of alpha rhythms to eyes opening (the Berger effect) during menstrual cycle phases
The impact of the menstrual cycle on the alpha EEG reactivity to eyes opening (Berger effect) was studied in relation to hormonal and EMG indices. Repeated measurements of salivary progesterone and cortisol, forehead EMG, and EEG alpha-activity indices in 76 healthy women aged 18-27 were obtained in resting eyes closed (1. min) and eyes open (30. s) conditions. Ten recording sessions occurred, at 2-3. day intervals, during 1-2 menstrual cycles. For example, if a participant had a menstrual cycle length of 30-32. days, she could finish the investigation during 1. cycle, but if she had a 24. day cycle, she would finish the investigation over 1 1/2. cycles. 6 women extended their investigation into a second cycle. The personal points of each woman's phase data were averaged before being used in group analyses.EEG and EMG responses to eyes open showed that magnitude of ¿-1 amplitude suppression corresponds to increasing EMG and salivary cortisol concentration only at the Follicular phase, when low alpha frequency waves are dominant in combination with low progesterone level. The magnitude of alpha suppression in response to eyes open in the upper ¿-2 frequency range does not vary with the menstrual cycle. The Luteal phase corresponds to the highest level of salivary progesterone and is associated with enhancement of the ¿-bandwidth. The most prominent reaction of salivary cortisol level, forehead EMG, and alpha EEG power to opening of the eyes occurs in the Follicular phase. This research reveals the dependence of the EEG Berger effect on the hormonal state and EEG alpha frequency.