Anterior Commissure - Sexuality

Sexuality

In 1992 Laura Allen and Roger Gorski of UCLA measured the anterior commissures of 30 homosexual men, 30 heterosexual men, and 30 heterosexual women. They found that all three groups' commissures were significantly different from one another, with homosexual males having the largest anterior commissure, followed by heterosexual women, and then heterosexual men, who had the smallest anterior commissures.

In 1993, a review by Byne and Parsons criticized this research, noting that 27 of the 33 homosexual males fell within the range of heterosexual males in the study. However, because range is defined only by the two most extreme data points in a group, the existence of a single heterosexual male with an exceptionally large anterior commisure for his group (an outlier ) would cause this large range irrespective of the data from the rest of the individuals in the group. This individual's existence would not change the fact that the groups on average were quite different from one another, and that these differences were statistically significant.

A later report by Byne et al. (2001) noted that

We also measured the anterior commissure in the same blocks of tissue used for the present hypothalamic study (data not shown) and were unable to replicate a report that its cross-sectional area is larger in women than in men.

Also, a study by Lasco et al. (2002) said:

We examined the cross-sectional area of the AC in postmortem material from 120 individuals, and found no variation in the size of the AC with age, HIV status, sex, or sexual orientation.