High estrogen levels in women while they are ovulating may be directly responsible for sluggishness or problems concentrating, a Canadian study released Friday has found.
Researchers at Concordia University's Center for Studies in Behavioral Neurobiology in Montreal linked high estrogen levels in laboratory rats to an inability to pay attention and learn.
These high levels have also been shown to interfere with women's ability to pay attention, but the study, to be published in the journal Brain and Cognition, is the first to show "how this impediment can be due to a direct effect of the hormone on mature brain structures," said a statement.
Both humans and rodents have similar brain physiology.
"Although estrogen is known to play a significant role in learning and memory, there has been no clear consensus on its effect," said study lead author Wayne Brake.
"Our findings ... show conclusively that high estrogen levels inhibit the cognitive ability in female rodents."
Researchers repeatedly exposed rats to a tone, with no consequences. Once they became used to it and ignored it, another stimulus was linked to the tone.
Rats with low levels of estrogen quickly learned that the tone was associated with the new stimulus whereas those with higher levels of estrogen took longer to form this memory.
"We only observed this effect in adult female rats," Brake said. "This and our other findings indicate that estrogen directly affects the brain, perhaps by interfering with brain signaling molecules."
The next step, he said, will be to determine how this occurs.