Brain activity linked to menstrual changes

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BLOOMINGTON, Ind., Nov. 12 (UPI) -- U.S. scientists have determined strong brain activity in the brains of women viewing masculinized male faces is most pronounced when they're ovulating.

Researchers at Indiana University's Kinsey Institute said it's been known a woman's preferences for masculine characteristics in men changes during the menstrual cycle. Through the new study, the scientists wanted to determine if those changes were linked with changes in brain activity.

Neuroscientist Heather Rupp and her team used computer imaging software to masculinize and feminize 56 male faces. The faces were shown to 12 heterosexual women with an average age of 25 years during a time they were close to ovulation, and during the luteal phase that begins after ovulation.

The researchers collected blood samples for hormone analyses and used functional MRI to measure brain activity in several brain regions.

The findings showed stronger responses to masculinized than feminized faces in brain regions related to face perception, decision making and reward processing when the women were closer to ovulation, the researchers said.

The study appears in the online edition of the journal Evolution and Human Behavior.