Sexual motivation: problem solved and new problems introduced

Background: During the past 50 years, motivational studies have evolved from the logical inference of logically required "intervening variables" to explain behavioral change, to electrophysiological and molecular analyses of the mechanisms causing such changes. Aim: The purpose of this review article is two-fold: first to describe the logic of sexual motivation in a way that applies to laboratory animals as well as humans, and the second is to address some of the problems of sexual motivation experienced by men. Results: When problems of motivational mechanisms are stripped down to their essentials, as performed in the laboratory animal models and are available for reductionistic studies, then the problems can be solved with certainty, as illustrated in the first part of this review. However, with respect to human sexual motivation, the various determinants which include so many behavioral routes and so many brain states come into play, that definite conclusions are harder to come by, as illustrated in the second part of this review. Conclusions: This review highlights a number of key questions that merit further investigation. These include (a) What mechanisms do cultural and experiential influences interact with androgenic hormone influences on human sexual motivation? (b) How would epigenetic effects in the human brain related to changes in motivation be investigated? (c) What are the effects of unpredictable traumatic and stressful human experiences on sexual motivation; (d) How such mechanisms are activated upon unpredictable traumatic and stressful insults? (e) What are the outstanding differences between sexual motivational drive and motivations driven by homeostatic systems such as hunger and thirst?