There is still a lack of knowledge regarding the brain regions involved in human sexual behavior in general, and orgasm in particular. In the last five years, we have performed a series of positron emission tomography (PET) experiments in healthy men and women to investigate the neuronal substrate of the orgasmic phenomenon. Orgasm-related brain perfusion appears to be similar in both sexes: compared to a baseline of sexual genital stimulation (high sexual arousal), orgasm-related activation was found in the medial part of the anterior cerebellum. Interestingly, orgasm-related deactivation was much more prominent, especially in the orbitofrontal cortex and the anterior temporal lobes. In women only, we also collected psychometric and physiological data. They were asked to rate their perceived level of sexual arousal (PSA), and, as a measure of pelvic muscle activity, their rectal pressure (RP) was measured. Positive correlations were found between RP-fluctuations and activation of the left deep cerebellar nuclei, and between PSA and activation of the ventral midbrain and right caudate nucleus. In the prefrontal cortex, the activation correlated negatively with RP-fluctuations, whereas PSA correlated negatively with the level of activation in the temporal lobes. Based on these findings in men and women, we propose that deactivation of the orbitofrontal cortex is associated with the behavioural disinhibition during orgasm, and that deactivation of the temporal lobe is directly related to high sexual arousal. The activated deep cerebellar nuclei may be involved in the orgasm-specific muscle contractions. Finally, the positive correlation between sexual arousal and activation of the ventral midbrain and caudate nucleus suggests a role for dopamine in sexual arousal and orgasm. These results expose neuronal mechanisms underlying sexual orgasm, and may help to understand and treat orgasmic disorders like premature ejaculation and anorgasmia.
Conflict of Interest: None disclosed
Financial Support/Funding: None disclosed
Recorded: Sydney, Australia, April 2007
more about this speaker
