[2] Homologs of the INAH-3 have been found to play a direct role in sexual behavior in quails,[3] rhesus macaques,[4] sheep,[5] rats,[6] mice,[7] and ferrets.
[8] The term INAH (interstitial nuclei of the anterior hypothalamus), first proposed in 1989 by a group of the University of California at Los Angeles, refers to 4 previously undescribed cell groups of the preoptic-anterior hypothalamic area (PO-AHA) of the human brain, which is a structure that influences gonadotropin secretion, maternal behavior, and sexual behavior in several mammalian species.
[9] A study authored by Simon LeVay and published in the journal Science suggests that the region is an important biological substrate with regard to sexual orientation.
The structural differences in INAH3 between homosexual and heterosexual males were present prenatally or in early life and aided in establishment of the men’s sexual orientation; 2.
Both the differences in INAH3 and sexual orientation are linked to some third confounding variable (such as a developmental event in prenatal or early life).