Appetitive and addictive factors pertinent to analysis of neuroscience studies of sexuality

Savic and Lindström (1) describe sexual dimorphism in the cerebral hemispheres and amygdala connectivity that is largely reversed in homosexual male and female subjects.

From a cultural perspective one of the most compelling issues raised by such documentation is the cause of the observed changes. Such mechanistic questions were not directly addressed by these authors (1), although they did note that genetic factors were unlikely to be major contributors. The final paragraph of their paper suggests that perceptual and behavioral factors are also unlikely to be implicated.

I found this comment strongly counterintuitive given the centrality of the reward circuitry including the amygdala and orbitofrontal cortex to appetitive behaviors including stereotypically sexuality; the almost holendemic use of addictive drugs in surveys of many particularly male homosexual populations and the well-described effects of addictive drugs on neuronogenesis, gliogenesis, and glia/neuronal fate determination and therefore potentially brain structure; and finally the high density particularly of CB1 endocannabinoid receptors in the cerebral cortex. No information on licit or illicit drug use was mentioned in the paper.

It would appear important that in future functional and morphologic brain studies on this issue careful consideration be given both to the likely impacts of altered appetitive and sexual behaviors on brain structure including gene expression–environment interactions and particularly to patterns of lifetime consumption of addictive agents, especially when both appetitive and toxicological exposures occur during periods of active brain maturation such as adolescence and early adulthood.