Nevertheless, such evidence should not preclude investigation of other factors, as reviewed by McCarthy, which may also play an important role in female development and sexual differentiation. As has been noted by other commentators, it seems likely that feminization, and indeed sexual differentiation in general, reflect highly complex interactions between intrinsic and extrinsic factors and a dynamic system. In Sexual Differentiation of the Brain. Ovarian estrogen acts to feminize the rat's corpus callosum. Morphological changes in the cerebral cortex of rats with altered levels of ovarian hormones.
Ovarian hormones act early in development to feminize open field behavior in the rat.