A woman's hormones affect specific
parts of the brain called the reward pathway, researchers
said in a finding that could offer insight into treating drug
abuse and mood disorders.
A study of women playing an imaginary slot machine game showed
their brain responses changed in anticipation of a payout
depending on the phases of their menstrual cycles.
This might help explain other studies that show women get
a bigger kick from cocaine and amphetamines during one phase
of the fertility cycle -- and perhaps why women are less vulnerable
to schizophrenia than men are, the researchers said.
"This demonstrates for the first time that female ... hormones
affect the reward system in very specific ways during particular
parts of the cycle," said Dr. Karen Berman of the U.S. National
Institute of Mental Health, who worked on the study published
in the Proceedings of the National Academy
of Sciences.
"It is interesting to speculate that this may have evolutionary
advantages and may affect behaviors that have been shown in
other studies to also be affected by cycles."
For instance, not only are women more susceptible to drug
abuse at certain points, but they may also find testosterone-type
facial traits in men more appealing at certain times in their
cycles, Berman said.
What this does not mean is that women are somehow more emotional
or vulnerable to hormones than men are, she stressed.
"I think it is important to keep in mind that this isn't
the only thing that is going on in women's brains," she said
in a telephone interview.
"We have very important regulatory areas and homeostatic
mechanisms that keep us in line, keep us functioning, keep
us focused, keep us productive," she added.
"I would really hate for this work to be interpreted in a
way to make us seem that we are at the call of our hormones
because I don't think that is the case."
Berman, working with Dr. Jean-Claude Dreher of France's national
scientific research center CNRS and colleagues, used functional
magnetic resonance imaging or fMRI to get real-time images
of the brain activity of 15 women.
The women played a hypothetical slot machine game, with payouts
of $10 or $20.
Different areas of the brain lit up in anticipation of a
payout -- a reward -- depending on the menstrual cycle phase.
For instance, during the midfollicular phase, which comes
four to eight days after menstrual bleeding starts, the orbitofrontal
cortex and amygdala of the brain were more active.
At this phase, estrogen is produced but progesterone levels
are low.
Berman said it is too soon to connect any of the findings
with specific behaviors.
Berman noted that estrogen has been found to protect brain
cells, and the findings could also shed light on other studies
of why women develop schizophrenia later in life than men
and at lower rates.
She would like to study women past menopause, who produce
much lower levels of hormones.
Hormones also affect the brains of men, but in different
ways, Berman said. Her team did not study men for this report.
