One reason for the high usage of sexually explicit material might be the rewarding property demonstrated in many studies showing an activation of the reward system during the presentation; no sex differences

No Sex Difference Found: Cues of Sexual Stimuli Activate the Reward System in both Sexes. Rudolf Stark et al. Neuroscience, August 5 2019. https://doi.org/10.1016/j.neuroscience.2019.07.049

Highlights
•    SEM cues resulted in similar neural activations as the presentation of SEM
•    The neural responses towards cues did not differ between men and women
•    There were some sex differences in the neural responses towards SEM
•    The nucleus accumbens response was unaffected by person characteristics

Abstract: Sexually explicit material (SEM) is increasingly used in western societies. One reason for this high usage might be the rewarding property of SEM demonstrated in many brain imaging studies showing an activation of the reward system during the presentation of SEM. It is not yet well understood why women use SEM to a remarkably lesser extent than men. Maybe men react stronger to stimuli – so called SEM cues –, which signal the presentation of SEM and are therefore more vulnerable to use SEM than women. Therefore, the present study aimed at investigating the sex specific neural correlates towards SEM and SEM cues. We were further interested in whether person characteristics as trait sexual motivation, extent of SEM use in the last month, and age at onset of goal-oriented SEM use affect the neural responses to SEM and SEM cues. The trials of the fMRI experiment consisted of an expectation phase with SEM or neutral cues and a presentation phase with SEM or neutral stimuli, respectively. Analyses showed that the reward circuitry was activated by SEM, but also by SEM cues. There were some sex differences in hemodynamic responses to SEM during the presentation phase, but not during the expectation phase to SEM cues in any of the regions of interest. The influence of the investigated person characteristics was only small if existent. The results suggest that sex specific cue processing cannot explain sex differences in the use of SEM.