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February 5, 2007

Brain's Reward Circuit Activity Ebbs And Flows With A Woman's Hormonal Cycle

Topics: Medicine
Brain%20activity.jpg

Leave it to medical researchers to spend time and money to tell us something that all of us already know: women's brains react to reward stimuli differently than men do and women respond to stimuli differently at various times during their ovulating cycle.

An imaging study at the National Institute of Mental Health (NIMH), a component of the National Institutes of Health (NIH), has revealed that fluctuations in sex hormone levels during women's menstrual cycles affect the responsiveness of their brains' reward circuitry.

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 are present. 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 phase. Men showed a different activation profile than women during both anticipation and delivery of rewards.

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 phase.

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.

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Posted by Richard at February 5, 2007 4:37 PM



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