|Brain’s Reward Circuit Activity Ebbs and
Flows with a Woman’s Hormonal Cycle
Fluctuations in sex hormone levels during women’s menstrual cycles
affect the responsiveness of their brains’ reward circuitry, an
imaging study at the National Institute of Mental Health (NIMH),
a component of the National Institutes of Health (NIH), has revealed.
While women were winning rewards, their circuitry was more active
if they were in a menstrual phase preceding ovulation and dominated
by estrogen, compared to a phase when estrogen and progesterone
“These first pictures of sex hormones influencing reward-evoked
brain activity in humans may provide insights into menstrual-related
mood disorders, women’s higher rates of mood and anxiety disorders,
and their later onset and less severe course in schizophrenia,” said
Karen Berman, M.D., chief of the NIMH Section on Integrative Neuroimaging. “The
study may also shed light on why women are more vulnerable to addictive
drugs during the pre-ovulation phase of the cycle.”
Berman, Drs. Jean-Claude Dreher, Peter Schmidt and colleagues
in the NIMH Intramural Research Program report on their functional
magnetic resonance imaging (fMRI) study online during the week
of January 29, 2007 in the Proceedings of the National Academy
Reward system circuitry includes: the prefrontal cortex, seat
of thinking and planning; the amygdala, a fear center; the hippocampus,
a learning and memory hub; and the striatum, which relays signals
from these areas to the cortex. Reward circuit neurons harbor receptors
for estrogen and progesterone. However, how these hormones influence
reward circuit activity in humans has remained unclear.
To pinpoint hormone effects on the reward circuit, Berman and
colleagues scanned the brain activity of 13 women and 13 men while
they performed a task involving simulated slot machines. The women
were scanned before and after ovulation.
The fMRI pictures showed that when the women were anticipating
a reward, they activated the amygdala and a cortex area behind
the eyes that regulates emotion and reward-related planning behavior
more during the pre-ovulation phase (four to eight days after their
period began) than in the post-ovulatory phase.
When they hit the jackpot and actually won a reward, women in
the pre-ovulatory phase activated the striatum and circuit areas
linked to pleasure and reward more than when in the post-ovulatory
The researchers also confirmed that the reward-related brain activity
was directly linked to levels of sex hormones. Activity in the
amygdala and hippocampus was in lockstep with estrogen levels regardless
of cycle phase; activity in these areas was also triggered by progesterone
levels while women were anticipating rewards during the post-ovulatory
phase. Activity patterns that emerged when rewards were delivered
during the post-ovulatory phase suggested that estrogen’s effect
on the reward circuit might be altered by the presence of progesterone
during that period.
Men showed a different activation profile than women during both
anticipation and delivery of rewards. For example, men had more
activity in a striatum (signal relay station) area during anticipation
compared to women and women had more activity in a frontal cortex
(executive hub) area at the time of reward delivery compared to
Also participating in the study were: Philip Kohn, Daniella Furman,
NIMH Section on Integrative Neuroimaging; and David Rubinow, NIMH
Behavioral Neuroendocrinology Branch.
|Brain activity in the orbitofrontal cortex (yellow), part of the brain's reward system, was increased during women's pre-ovulatory (follicular) menstrual phase compared to their-post-ovulatory (luteal) phase while they were anticipating winning money. Located just behind the eyes, this area is thought to regulate emotion and reward-related planning behavior. Functional MRI data superimposed on structural MRI scan.
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