Effects of Sex Steroid Levels on the Spectral Power of Neocortical EEG in Female WAG/Rij Rats

This study investigated the effects of different sex steroid levels on the spectral characteristics of neocortex EEG in female WAG/Rij rats. The experiment was performed on three groups of animals: control (diestrus), after ovariectomy, and after hormone replacement therapy (17β-estradiol + progesterone). Spectral analysis of EEG from the frontal and parietal regions revealed region-specific changes. In the frontal cortex, ovariectomy caused a significant increase in delta power (from 39.78% to 57.70%) and a decrease in theta and low-frequency beta activity, whereas the parietal cortex showed an increase in theta rhythm and a tendency toward decreased alpha and beta activity. Hormone replacement therapy did not fully restore the spectral parameters to control levels. These data indicate region-specific modulatory effects of estrogens on cortical electrical activity and confirm the high value of EEG spectral analysis for identifying neurophysiological markers of sex hormone deficiency.