Women born amongst a rare status that gives them a Y chromosome don't alone expect similar women physically, they besides convey the same encephalon responses to visual sexual stimuli, a novel written report shows.
The journal Hormones as well as Behavior published the results of the outset encephalon imaging written report of women amongst consummate androgen insensitivity, or CAIS, led yesteryear psychologists at Emory.
"Our findings clearly dominion out a straight number of the Y chromosome inwards producing masculine patterns of response," says Kim Wallen, an Emory professor of psychology as well as behavioral neuroendocrinology. "It's farther prove that nosotros postulate to revamp our thinking almost what nosotros hateful yesteryear 'man' as well as 'woman.'"
Wallen conducted the enquiry amongst Stephan Hamann, Emory professor of psychology, as well as graduate students inwards their labs. Researchers from Pennsylvania State University as well as Indiana University besides contributed to the study.
The Y chromosome was identified equally the sex-determining chromosome inwards 1905. Females commonly convey an XX chromosome brace as well as males convey an XY chromosome pair.
By the 1920s, biochemists besides began intensively studying androgens as well as estrogens, chemic substances commonly referred to equally "sex hormones." During pregnancy, the presence of a Y chromosome leads the fetus to ambit testes. The testes as well as hence secrete androgens that possess the formation of a penis, scrotum as well as other manful individual characteristics.
Women amongst CAIS are born amongst an XY chromosome pair. Because of the Y chromosome, the women convey testes that stay hidden inside their groins but they lack neural receptors for androgens hence they cannot respond to the androgens that their testes produce. They can, however, respond to the estrogens that their testes ambit hence they prepare physically equally women as well as undergo a feminizing puberty. Since they ambit non convey ovaries or a uterus as well as ambit non menstruate they cannot convey children.
"Women amongst CAIS convey androgen floating around inwards their brains but no receptors for it to connect to," Wallen says. "Essentially, they convey this default woman individual designing as well as it's equally though they were never exposed to androgen at all."
Wallen as well as Hamann are focused on teasing out neural differences betwixt men as well as women. In a 2004 study, they used functional magnetic resonance imaging (fMRI) to written report the neural activeness of typical men as well as typical women piece they were viewing photos of people engaged inwards sexual activity.
The patterns were distinctively clear, Hamann says. "Men showed a lot to a greater extent than activeness than women inwards 2 areas of the encephalon -- the amygdala, which is involved inwards emotion as well as motivation, as well as the hypothalamus which is involved inwards regulations of hormones as well as perchance sexual behavior."
For the most recent study, the researchers repeated the experiment piece besides including xiii women amongst CAIS inwards add-on to women without CAIS as well as men.
"We didn't uncovering whatever divergence betwixt the neural responses of women amongst CAIS as well as typical women, although they were both real unlike from those of the men inwards the study," Hamann says. "This final result supports the theory that androgen is the commutation to a masculine response. And it farther confirms that women amongst CAIS are typical women psychologically, equally good equally their physical phenotype, despite having a Y chromosome."
A limitation of the written report is that it did non mensurate environmental effects on women amongst CAIS. "These women expect the same equally other women," Wallen explains. "They're reared equally girls as well as they're treated equally girls, hence their whole developmental sense is feminized. We can't dominion out that sense equally a element inwards their encephalon responses."
The findings may convey broader applications inwards knowledge as well as health. "Anything that nosotros tin laissez passer on the axe acquire almost gender differences inwards the brain," Wallen says, "may help response of import questions such equally why autism is to a greater extent than mutual inwards males as well as low to a greater extent than mutual inwards females."