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 are present.
My guess is that it is more rewarding to be around women who are in their pre-ovulatory phase.
What is the purpose of this effect of neurons on reward centers? Is it to make women get greater enjoyment from sex when they are more likely to get pregnant?
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 phase.
Both reward anticipation and reward reception were enhanced by estrogen.
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.
So then do women enjoy life less after they've ovulated? Also, do women on birh control pills get more or less pleasure from rewards? Same question for post-menopausal women who have less estrogen in their bodies? Do they get less of a thrill from rewards?
What is going to happen with this information in the long run? Imagine drugs that cause or block the effects of estrogen on reward centers and pleasure-related neurons. Will women choose to have their minds always in the pre-ovulatory state and feel more reward from wins and gains? Or will they choose to block the effects of higher estrogen on their brains?
|Share |||Randall Parker, 2007 February 03 02:51 PM Brain Sexuality|