Homosexual Women Have Less Grey Matter in Perirhinal Cortex than Heterosexual Women

Abstract

Is sexual orientation associated with structural differences in the brain? To address this question, 80 homosexual and heterosexual men and women (16 homosexual men and 15 homosexual women) underwent structural MRI. We used voxel-based morphometry to test for differences in grey matter concentration associated with gender and sexual orientation. Compared with heterosexual women, homosexual women displayed less grey matter bilaterally in the temporo-basal cortex, ventral cerebellum, and left ventral premotor cortex. The relative decrease in grey matter was most prominent in the left perirhinal cortex. The left perirhinal area also showed less grey matter in heterosexual men than in heterosexual women. Thus, in homosexual women, the perirhinal cortex grey matter displayed a more male-like structural pattern. This is in accordance with previous research that revealed signs of sex-atypical prenatal androgenization in homosexual women, but not in homosexual men. The relevance of the perirhinal area for high order multimodal (olfactory and visual) object, social, and sexual processing is discussed.

Regional gray matter variation in male-to-female transsexualism

“…Given this unequal distribution and given that information on sexual orientation was unavailable for control subjects, we abstained from conducting analyses for different subtypes. However, a number of previous findings appear to indicate brain-structural alterations associated with sexual orientation (Allen and Gorski, 1992; Byne et al, 2001; LeVay, 1991; Ponseti et al, 2007; Savic and Lindstrom, 2008; Swaab and Hofman, 1990; Witelson et al, 2008). Moreover, a highly controversial line of research has suggested that homosexual and non-homosexual MTF transsexualism are etiologically heterogeneous (Blanchard, 1989a; Blanchard, 1989b), which may be associated with differences in neuroanatomy.…”

A neural circuit encoding sexual preference in humans

“…The corresponding cluster of convergent activity also comprised the left perirhinal cortex. Interestingly, gray matter of this region displays a more male-like structural pattern in homosexual women (Ponseti et al, 2007). Together, these findings can be interpreted as support for sex-atypical prenatal androgenization in homosexual women and for early determination of sexual preference in the fetal stage on the basis of hormonal influence in general.…”

Manual activity shapes structure and function in contralateral human motor hand area

“…VBM of T1-weighted MRI images has identified areas in the brain where regional grey matter volume is correlated with individual variations in genotype (Binkofski et al, 2007;Pezawas et al, 2004), motor skills (Gaser and Schlaug, 2003), topographical memory (Maguire et al, 2003), or sexual orientation (Ponseti et al, 2007).…”