Can the Vaginal Photoplethysmograph and Its Associated Methodology Be Used to Assess Anal Vasocongestion in Women and Men?

Forty years ago, researchers documented changes in vascular and muscular activity within the anal canal of women and men who engaged in sexual self-stimulation. Vascular changes were assessed using a photoplethysmograph that aimed to detect changes in pelvic vasocongestion. An important advantage of detecting sexual response within the anal canal is that the device, its anatomical placement, and the data output are identical for women and men, therefore facilitating gender comparisons of response patterns. In this study, the vaginal photoplethysmograph (VPP), the most common measure of genital response in women, was administered intra-anally as an anal photoplethysmograph (APG) to examine its validity and sensitivity as an indicator of sexual response. The final sample comprised 20 women and 20 men who were exposed to 12, 90-s sexual and nonsexual film clips while their APG responses were recorded. Participants also rated their sexual arousal and affective responses to the stimuli. There was evidence that APG responses were specific to sexual stimuli and were sensitive to erotic intensity in women. The degree of discrimination between sexual and nonsexual stimuli was lower in men. Unlike most sexual psychophysiological studies, the positive correlation between physiological and self-reported sexual arousal was stronger in women than in men. There was a relatively high number of data artifacts and the waveform morphology was uncharacteristic of that typically observed with VPP. The potential role of anal musculature interference on the APG signal is discussed, as well as avenues for future research.