Women go through hormonal fluctuations each month during their menstrual cycle that influence behavior, emotions and overall mood.
For some women, ovulation will bring on a slew of symptoms before menstruation even begins, including a higher sex drive, a change in basal body temperature or a heightened sense of taste, smell or vision. But according to a recent study conducted by researchers at the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig, Germany, a silent symptom of menstruation goes unnoticed by women: brain growth.
The study found a correlation between estrogen levels throughout the menstrual cycle and the female brain. In parallel to the rhythm of the level of estrogen across their menstrual cycle, the structures of the hippocampus – a small region of the brain that is vital for emotions, mood and memories – vary in women. As the levels of estrogen rise approaching ovulation, the hippocampus increases in volume, in terms of both grey matter and white matter.
Previous studies have found that estrogen can directly affect the hippocampus when it comes to synapses, the areas where connections to other cells are located. Estrogen increases the synaptic connectivity in the hippocampus significantly, enhancing communication between neurons.
Researchers at the Max Planck Institute for Human Cognitive and Brain Sciences measured the estrogen levels in 30 women across two full menstrual cycles. These women then underwent MRI scans that were used to measure the volume of the different regions within each woman’s brain.
The results of the study found brain growth in both gray matter- where the synapses are located- and white matter- where the nerve fibers are located. The fluctuating estrogen levels altered the structure of the brain in surprising regularity.
It’s still unclear as to how these monthly changes in the hippocampus’ volume impact women’s daily lives, but researchers have begun to make their own hypotheses based on previous studies. In 2014, a study published in the Journal of Neuroscience found the rise of estrogen levels during the menstrual cycle can help deter women from making impulsive decisions as compared to the impulsive behaviors that can be seen in some women at the beginning of menstruation when estrogen levels are still low.
In an interview with Medical Daily, Dr. Ben Michaelis, a clinical psychologist explained that estrogen-progesterone surges can influence a woman’s mood, her self-esteem, and how she connects to others.
“Estrogen levels are closely linked with women’s emotional well-being as estrogen affects parts of the brain that control emotions,” Michaelis stated.
Researchers hope to continue their study with a larger group of women to examine the overall effects of the growth in the hippocampus on the behavior of women. The goal is to gain further insight into premenstrual dysphoric disorder (PMDD), which affects one in 12 women in the days leading up the menstrual cycle and includes symptoms such as severe mood swings and anxiety. If women are particularly receptive in certain phases of their menstrual cycle to making changes in and to their behavior, researchers believe that this could be a good time for PMDD patients to undergo therapy.
However, they first need to find out which monthly rhythm the brain of a healthy woman follows to reveal the differences in people affected by PMDD.
Once science investigates how exactly the hippocampus influences behavior, women will gain a better understanding for what motivates actions, especially during the menstrual cycle.
“To get a better understanding of this disorder, we first have to find out which monthly rhythm the brain of a healthy woman follows,” co-author Julia Sacher, a research leader at the Max Planck Institute noted in a statement. “Only then can we reveal the differences in persons affected by PMDD.”
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