A phenomenon known as "momnesia" or "pregnancy brain" affects many women during pregnancy, causing forgetfulness, mental fogginess, and cognitive changes. Scientists have now found a possible explanation, identifying a specific brain circuit that becomes disrupted under high estrogen levels. Experiments using laboratory mice designed to mimic sustained elevated estrogen during pregnancy led to temporary memory impairment without mood changes. This impairment was linked to changes in a neuronal pathway between the hypothalamus and hippocampus.
The study, published in the journal Science Bulletin, was led by Dr. Zheng Sun, a professor of medicine at Baylor College of Medicine. According to Dr. Sun, "momnesia" becomes most evident in late pregnancy and may continue into the postpartum period but usually dissipates after childbirth. Short-term and long-term memory can be affected, including spatial, social, and verbal memory. Examples of "momnesia" include forgetting why one entered a room, misplacing an item, or struggling to recall familiar information.
The researchers found that high estrogen levels increased the activity of hypothalamus neurons, which in turn suppressed activity in the hippocampus and impaired memory. This effect was linked to a protein called "estrogen receptor alpha," which transmits estrogen's signals into cells in the hypothalamus. The hypothalamus acts as a control center and integrative hub, while the hippocampus is central to memory formation.
The study suggests that "momnesia" does not represent a general decline in cognitive ability. According to Dr. Yanlin He, director of the Brain Glycemic and Metabolism Control Laboratory at Louisiana State University's Pennington Biomedical Research Center, "the effects appear to be more subtle and specific to certain cognitive tasks." The findings indicate that pregnancy does not simply make someone "less intelligent."
The mouse experiments shed light on what is happening in the brain during pregnancy. Estrogen levels increase during pregnancy, peaking in the third trimester. The researchers designed the experiments to mimic this sustained elevated estrogen, allowing them to study its effects on the brain. The results provide new insights into the biological phenomenon of "momnesia."
According to Dr. Sun, about 80% of pregnant women notice changes in their memory and cognitive function, although this figure largely reflects self-report and subjective experience. The study's findings may help alleviate concerns for women experiencing "momnesia," as it suggests that the effects are temporary and specific to certain cognitive tasks.
The research team hopes that their findings will contribute to a better understanding of the biological changes that occur during pregnancy. By identifying the specific brain circuit affected by high estrogen levels, scientists may be able to develop new treatments or strategies to support women's cognitive health during pregnancy and beyond.
Key points
- Scientists identify a brain circuit disrupted by high estrogen levels during pregnancy, leading to temporary memory impairment.
- The phenomenon of "momnesia" affects about 80% of pregnant women and is characterized by forgetfulness, mental fogginess, and cognitive changes.
- The study suggests that "momnesia" does not represent a general decline in cognitive ability, but rather a subtle and specific effect on certain cognitive tasks.
