Sexual Orientation May Affect Brain Response to Human Pheromones
. . .
May 8, 2006 -- Lesbian women and heterosexual women respond differently to the scent of human pheromones, a new study shows.
The researchers studied brain scans of lesbian women, heterosexual women, and heterosexual men while those people smelled scents including two potential human pheromones.
Brain scans taken while smelling those pheromones were more similar for lesbian women and heterosexual men than for lesbian women and heterosexual women, the researchers report. Their study appears in the online early edition of Proceedings of the National Academy of Sciences. [Not yet, check back tomorrow.]
Last year, Savic's team published a study showing that homosexual men and heterosexual women had similar brain activity patterns when smelling those same human pheromone candidates. [See below.]
Brain response to putative pheromones in homosexual men. . .
Ivanka Savic, Hans Berglund, and Per Lindström
PNAS | May 17, 2005 | vol. 102 | no. 20 | 7356-7361
The testosterone derivative 4,16-androstadien-3-one (AND) and the estrogen-like steroid estra-1,3,5(10),16-tetraen-3-ol (EST) are candidate compounds for human pheromones. AND is detected primarily in male sweat, whereas EST has been found in female urine. In a previous positron emission tomography study, we found that smelling AND and EST activated regions covering sexually dimorphic nuclei of the anterior hypothalamus, and that this activation was differentiated with respect to sex and compound. In the present study, the pattern of activation induced by AND and EST was compared among homosexual men, heterosexual men, and heterosexual women. In contrast to heterosexual men, and in congruence with heterosexual women, homosexual men displayed hypothalamic activation in response to AND. Maximal activation was observed in the medial preoptic area/anterior hypothalamus, which, according to animal studies, is highly involved in sexual behavior. As opposed to putative pheromones, common odors were processed similarly in all three groups of subjects and engaged only the olfactory brain (amygdala, piriform, orbitofrontal, and insular cortex). These findings show that our brain reacts differently to the two putative pheromones compared with common odors, and suggest a link between sexual orientation and hypothalamic neuronal processes.
Savic's latest study included 12 heterosexual men, 12 lesbian women, and 12 heterosexual women. All were healthy and not taking medication.
The lesbian women had normal hormonal levels. Regardless of sexual orientation, the women were studied at the same point in their menstrual cycle.
Participants were given glass bottles containing scents including AND, EST, lavender oil, or cedar oil. Each bottle only contained one scent.
Meanwhile, the researchers scanned participants' brains with magnetic resonance imaging (MRI) and positron emission tomography (PET) technology. Afterward, participants rated the scents for pleasantness, irritability, intensity, and familiarity.
Lesbian and heterosexual women showed different patterns of brain activity while sniffing AND and EST, the study shows.
While smelling AND and EST, the brain activity pattern for lesbian women was closer to that of heterosexual men than heterosexual women, Savic and colleagues note.
However, the previously reported similarities between brain activity for heterosexual women and homosexual men while sniffing the pheromones were stronger than those between lesbian women and heterosexual men.
The pheromones didn't necessarily have a sexy smell. "None of our subjects reported sexual arousal" while whiffing any of the scents, the researchers write.
[with a "straight" face, I presume??]
Lesbians' Brains React DifferentlyWhile we're at it:
. . .
Heterosexual women found the male and female pheromones about equally pleasant, while straight men and lesbians liked the female pheromone more than the male one. Men and lesbians also found the male hormone more irritating than the female one, while straight women were more likely to be irritated by the female hormone than the male one.
All three groups rated the male hormone more familiar than the female one. Straight women found both hormones about equal in intensity, while lesbians and straight men found the male hormone more intense than the female one.
The brains of all three groups were scanned when sniffing male and female hormones and a set of four ordinary odors. Ordinary odors were processed in the brain circuits associated with smell in all the volunteers.
In heterosexual males the male hormone was processed in the scent area but the female hormone was processed in the hypothalamus, which is related to sexual stimulation. In straight women the sexual area of the brain responded to the male hormone while the female hormone was perceived by the scent area.
In lesbians, both male and female hormones were processed the same, in the basic odor processing circuits, Savic and her team reported.
Sex-specific influences of vasopressin on human social communication
R. R. Thompson, K. George, J.C. Walton, S.P. Orr, and J. Benson
Proc. Natl. Acad. Sci. USA, 10.1073/pnas.0600406103
Published online before print May 8, 2006
Arginine vasopressin (AVP) and related peptides affect social behaviors in numerous species, but AVP influences on human social functions have not yet been established. Here, we describe how intranasal AVP administration differentially affects social communication in men and women, and we propose a mechanism through which it may exert those influences. In men, AVP stimulates agonistic facial motor patterns in response to the faces of unfamiliar men and decreases perceptions of the friendliness of those faces. In contrast, in women, AVP stimulates affiliative facial motor patterns in response to the faces of unfamiliar women and increases perceptions of the friendliness of those faces. AVP also affected autonomic responsiveness to threatening faces and increased anxiety, which may underlie both communication patterns by promoting different social strategies in stressful contexts in men and women.
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