The structure of the female brain changes throughout the menstrual cycle, scientists have found.
For the first time, researchers at Germany's Max Planck Society have monitored how the brain changes at different stages of the menstrual cycle, providing a valuable steppingstone for the development of sex-specific strategies to improve brain health and mental well-being.
"In general, the female brain is still massively understudied in cognitive neuroscience," the study's co-author, Julia Sacher, said in a statement.
She went on: "Even though sex steroid hormones are powerful modulators of learning and memory, less than 0.5 percent of the neuroimaging literature considers hormonal transition phases, such as the menstrual cycle, the influence of hormonal contraceptives, pregnancy and menopause. We are committed to addressing this fundamental research gap."
The menstrual cycle is characterized by fluctuating levels of various reproductive hormones. During the first half of the cycle, the hormone estrogen steadily rises until ovulation, while progesterone dominates the second half of the cycle.
During each menstrual cycle, estrogen levels are thought to increase by a factor of eight, while progesterone levels increase eightyfold. Both of these hormones have been shown to affect brain activity but previous studies have not observed how their rising and falling levels throughout the month can affect brain structure.
In a study published October 5 in the journal Nature Mental Health, Sacher and her team used an MRI scanner to map the structure of specific brain regions in 27 female participants of reproductive age at six different points throughout their menstrual cycle.
"We were able to determine that certain medial temporal lobe regions, which are crucial for episodic memory and spatial cognition, expand under high estradiol [the most potent form of estrogen] and low progesterone levels," Sacher said. "That is, these brain areas remodel themselves in synchronization with the menstrual cycle."
These results may also explain why the rapid hormonal changes that accompany early menopause can affect memory and cognition.
By improving our understanding of how the healthy female brain fluctuates throughout the month, we may be able to better support individuals with brain-related disorders.
"To identify the mechanisms underlying risk and resilience to mental health disorders, such as depression or Alzheimer's disease, we need a deeper understanding of how the healthy female brain adapts to change," Sacher said.
"We want to clarify whether these rhythmic changes are altered in individuals at risk for memory and affective disorders in several follow-up studies," she said.
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