Abstract
Estradiol and progesterone vary along the menstrual cycle and exert opposite effects on a variety of neurotransmitter systems. However, few studies have addressed menstrual cycle-dependent changes in the brain. In the present study we investigate menstrual cycle changes in brain activation and connectivity patterns underlying cognition. Thirty-six naturally cycling women underwent functional MRI during two cognitive tasks: spatial navigation and verbal fluency. While no significant performance differences were observed along the menstrual cycle, the changes in brain activation patterns are strikingly similar during both tasks. Irrespective of the task, estradiol boosts hippocampal activation during the pre-ovulatory cycle phase and progesterone boosts fronto-striatal activation during the luteal cycle phase. Connectivity analyses suggest that the increase in right-hemispheric frontal activation is the result of inter-hemispheric decoupling and is involved in the down-regulation of hippocampal activation.
Highlights
Estradiol and progesterone levels fluctuate along the female menstrual cycle [1]. While both hormones are low during menses, estradiol peaks in the pre-ovulatory phase to drop again and rise to medium levels in the mid-luteal phase
Brain activation Effect sizes and standard errors for menstrual cycle effects are summarised in Supplementary Table 1
The present study set out to investigate menstrual cycle effects on brain activation in two different cognitive tasks, focusing on areas that emerged as targets for sex hormone actions in animal and human studies
Summary
Estradiol and progesterone levels fluctuate along the female menstrual cycle [1]. While both hormones are low during menses, estradiol peaks in the pre-ovulatory phase to drop again and rise to medium levels in the mid-luteal phase. Progesterone is generally low prior to ovulation and rises to peak levels in the mid-luteal phase. Neuroactive effects of sex hormones have received increasing attention and have been ascribed a modulatory role in cognitive functions [2, 3]. Neuroimaging studies suggest that not all neuroactive effects of sex hormones are immediately reflected at the performance level [14,15,16,17,18,19,20]. If compensatory mechanisms are at play, no changes in performance are expected, while changes in brain activation and connectivity could shed light on the underlying neuronal circuitry supporting task performance
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