The way in which women problem solve seems to change across their cycle.
The degree to which women's cognitive abilities are influenced by their cycling hormones has long been questioned by scientists and lay people alike.
Recent research does not fully answer this question, but it does give a fascinating new insight.
The way in which women approach a problem seems to be heavily dependent on the phase of their menstrual cycle.
Studies have shown that the two hormones have specific effects on various parts of the brain and, as the cycle waxes and wanes and hormone levels follow suit, certain brain areas are activated to greater or lesser extents.
In rat studies, researchers have shown that, depending on estrogen status, rats "will use one type of memory system or strategy versus another to solve a maze."
Memory strategies in rats
During times of low estradiol (the most potent and prevalent type of estrogen in the human body) rats will use memory systems that involve the striatum; and, at times of high estradiol, hippocampal-dependent memory is used preferentially.
The hippocampus is implicated in spatial memory, and the dorsal striatum is important for response memory - a type of memory that pairs physical actions with the environment around us.
These separate problem-solving strategies are not necessarily better or worse than each other, they simply approach problems from different directions and compete with each other within a single brain.
Recent Ph.D. graduate, Dema Hussain, lead author of the study described below, set out to investigate this effect in the human population for the first time.
"Women have sometimes reported to doctors that their memory works differently depending on which phase of the menstrual cycle they are in - even during and following pregnancy, or following menopause.
This has led scientists to wonder whether estrogen and progesterone could affect memory and problem solving."
Prof. Wayne Brake, co-author
The investigation was carried out at Concordia University in Montreal, Canada; it involved 45 participants with regular menstrual cycles.
Estrogen and cognitive strategies
To begin with, the researchers studied each woman's individual "hormonal profile." This involved gathering detailed information regarding their periods, contraceptive and synthetic hormone intake, past pregnancies, and other life habits.
Participants were next split into groups dependent on their current position within the menstrual cycle. The groups were defined as early follicular (low estradiol levels), ovulatory (high estradiol levels), and mid/late luteal (end of the cycle, where estradiol drops and progesterone rises).
Blood tests were used to confirm each participant's phase within the cycle.
To assess their cognitive strategies, each woman was asked to complete a virtual navigation task. The task, known as dual-solution navigation task, takes the form of a maze within a video game. As its name suggests, there are two ways to solve the problem, one relies on spatial memory (for instance, using landmarks), the other requires a response memory method.
In addition to the maze task, participants completed a battery of standard verbal and visuospatial memory tasks.
Once the data had been analyzed, the results were clear: women who were ovulating performed better in memory tasks, such as memorizing lists of words, and women in their pre-menstrual phase (mid/late luteal) were better at solving the spatial navigation trial.
The authors conclude that how women use specific strategies to approach problems depends on their current menstrual phase. Rather than the standard theory that hormones simply impair or improve cognitive ability, it seems that hormones influence the type of cognitive system they use.
This could have broad ramifications when considering how scientists approach research.
"Traditionally, researchers and scientists have relied on using male participants - and male rats - in studies to develop drugs and treatments for the general population. But we now know that women respond differently than men."
Dema Hussain, Ph.D., lead author
Hussain hopes that her research will inspire further experiments designed to delve into the fascinating effects of estrogen on the brain.