5 December 2005
Menstrual Cycle Rewires Brain
by Kate Melville
Confirming what women have known for years, researchers have found that changes in hormone levels can have dramatic effects on the female brain. While the new findings lend weight to the old time-of-the-month cliché, they should also raise concerns about the effects that various hormonal treatments, such as the birth control pill, may have on the brain.
The findings - presented at the 2005 Society for Neuroscience Meeting - show that the "wiring" in the brains of female rats expands and contracts in relation to the amount of estrogen present during the menstrual cycle.
The area of the brain in question, the hippocampus, has been shown to be critical to both humans and animals for memory processes. The findings lend support to a huge amount of empirical and anecdotal evidence concerning variations in cognition and memory processes as a function of the female cycle.
The researchers - from Northwestern University and Columbia University - showed that this rewiring was due to estrogen by using hormone replacement therapy to compare females with low, moderate or high levels. It was only when the high physiological level was reached - similar to that seen during the peak of estrogen levels during the cycle - that the growth was observed.
Looking at the findings from an evolutionary viewpoint, the researchers suggest that the ability of the female brain to modify itself in the presence of increased estrogen may facilitate processing of complex spatial environments to enhance reproductive success, for example, selecting a mate or, as a mother, finding food, water and shelter while avoiding predators.
Researcher Aryeh Routtenberg said that the growth they observed resembled that seen during learning, but learning growth was a much slower process. "Beyond the findings relative to estrogen, and its regulation of female cognition, the results of the study suggest that the brain's capacity for growth is well beyond anything we considered in the past."
Source: Northwestern University