In the brain, the sexually dimorphic nucleus of the preoptic area (SDN-POA) is a key region which differs between males and females in humans and a number of mammals (e.g., sheep/rams, mice, rats), and is caused by sex differences in hormone exposure. Also, the INAH-3 region is bigger in males than in females, and is known to be critical for sexual behavior. Dissection studies found that gay men had significantly smaller INAH-3 than heterosexual men, a shift in the female direction, as first demonstrated by neuroscientist Simon LeVay, which has been replicated. Dissection studies are rare, however, due to lack of funding and brain samples.
In the brain, the sexually dimorphic nucleus of the preoptic area (SDN-POA) is a key region which differs between males and females in humans and a number of mammals (e.g., sheep/rams, mice, rats), and is caused by sex differences in hormone exposure Also, the INAH-3 region is bigger in males than in females, and is known to be critical for sexual behavior. Dissection studies found that gay men had significantly smaller INAH-3 than heterosexual men, a shift in the female direction, as first demonstrated by neuroscientist Simon LeVay which has been replicated. Dissection studies are rare however, due to lack of funding and brain samples.