We found that the [brain areas] amygdala and hypothalamus were more activated in men than in women when viewing identical sexual stimuli, even when females reported greater arousal," writes Hamann.
In fact, men and women both rated the erotic photographs as sexually attractive and physically arousing. Both groups also found the photos of the couples more attractive and arousing than the photographs depicting a nude person of the opposite sex.
However, in a closer look at responses to the photographs of couples -- which got the biggest arousal from both men and women -- men had greater activity in the amygdala and hypothalamus than did women, writes Hamann. Women showed no significant activation in these regions.
Men also revealed a "greater propensity" for finding even the "neutral" photographs arousing -- although to a lesser degree, reports Hamann. This pattern may reflect what other sex drive studies have found, that across all cultures men prefer sexual variety more than women, he says.
Inside the Amygdala
The amygdala has multiple functions, although its prime role is processing emotions, Hamann explains.
The amygdala plays an important role in survival -- in quickly determining what's good and what's threatening, Hamann writes.