Gay men and straight women share some characteristics in the area of the brain responsible for emotion, mood and anxiety, a new study finds.

Brain scans also showed brain similarities between lesbians and straight men, according to the study, which appears in the current issue of the Proceedings of the National Academy of Sciences.

Differences both in the brain activity and anatomy were observed in a study of 90 men and women, including homosexuals and heterosexuals of both genders.

The researchers monitored neural activity in the brain by charting blood flow.

Researchers focused in particular on the amygdala, an almond-shaped structure inside each brain hemisphere associated with processing and storing emotions. They found that brain activity in homosexuals was similar to that of heterosexuals of the opposite sex.

The right hemisphere was found to be slightly larger than the left in heterosexual males and lesbians, whereas the two hemispheres in the brains of gay men and straight women were symmetrical.

Researchers were unable to determine whether the differences in brain shape are genetic or due to exposure to environmental hormones, such as testosterone, while in the womb. The study also was unable to conclude whether the differences are responsible for sexual orientation.

Click here to comment on this story.

Click here for more on this study published in the Proceedings of the National Academy of Sciences.