The Psychophysiology of Sex

Discussion Paper

Discussion Paper serge stoléru The starting point of the dual control model, the DCM, is the proposition that in studying sexual arousal we may have to discern both excitatory and inhibitory in®uences. This proposition really sets the stage for research on the regulation of sexual arousal. I think it’s a heuristic proposition within which research can be conducted with a clear starting point. It gives to sexual arousal the same status as other motivational entities such as hunger or thirst, in that it suggests we should try to understand not only the mechanisms that give rise to these motivational states, but also those mechanisms that regulate their level of intensity and that lead to a state of restraint or satiety. In this brief discussion, I shall mainly use the insights we have gained through studies of sexual arousal based on brain functional imaging. The sequence of my comments will follow the order of issues presented in the paper that we have just listened to. In the paper’s introduction, the authors write that “no models or measures existed that focus speci¤cally on individual differences in sexual response.” The development by the authors of the Sexual Inhibition Scales/Sexual Excitation Scales or SIS/SES questionnaire has purported to provide measures that would reveal and quantify individual variability in sexual responsiveness. However, isn’t it the case that previous measures of arousal or of desire, such as the Sexual Arousal Inventory (Hoon, Hoon, & Wincze, 1976), were designed to assess such individual variability? Thus, it seems to me that the originality, the real importance of the SIS/SES questionnaire and its speci¤c contribution, is that it provides an assessment of inhibitory psychological in®uences. The DCM “postulates the involvement of two neurophysiological systems , one relevant to the activation, the other to the suppression of sexual response.” Brain functional imaging studies suggest that the neurophysiological system relevant to the suppression of the sexual response is comprised of several components that operate at different stages of the sexual response. Therefore, based on ¤ndings from brain functional imaging studies , it would seem useful to explore and measure the various psychological inhibitory factors that correspond to the different inhibitory neurophysiological systems. First, neuroimaging studies suggest the existence of permanent tonic inhibitory control that prevents the unfolding of sexual 223 arousal. When a potential sexual stimulus is presented to the subject, this tonic inhibitory control may be alleviated. If, instead of laboratory conditions , we consider everyday situations; for example, if a person is reading a book in a library and an attractive person walks nearby, the person may stop reading and start to have sexual fantasies. The previous state of sexual quiescence is terminated. We suspect that this ¤rst kind of inhibitory system , which accounts for sexual quiescence, is neurally mediated by temporal areas. This would mean that sexual quiescence is not simply a “default mode,” but an actively maintained state. In various samples to which we presented visual sexual stimuli, we obtained a response in temporal areas that was not activation, but deactivation. What this means is that the blood®ow in these regions decreased. In monkeys, the experimental bilateral removal of the temporal cortex, including the medial aspects of the temporal cortex, is followed by dramatic hypersexuality and frantic sexual activity, called the Klüver and Bucy syndrome. However, the idea that temporal areas mediate sexual quiescence is only an interpretation and the decrease of regional blood ®ow in temporal areas may be explained by other interpretations . At least in humans, one could argue, for instance, that deactivation of temporal areas re®ects the fact that in response to visual sexual stimulation, a person is ceasing to have intellectual thoughts. Thus, deactivation of temporal areas doesn’t necessarily mean that those areas are exerting inhibitory control, but the Klüver and Bucy syndrome adds support to this interpretation. A second neurophysiological system is what I refer to as a devaluation system: at least in patients with hypoactive sexual desire disorder (HSDD), but possibly in milder forms in healthy subjects, it is a system that will mediate a critical evaluation of the object of desire and will disconnect the perception of this object from the regions implicated in motor imagery and sexual motivation. This is the way we have interpreted the lack of deactivation of the medial orbitofrontal cortex in patients with HSDD. This is what I showed you this morning, of course. There has been recent support for this interpretation in...