The Clitoral Photoplethysmograph: A New Way of Assessing Genital Arousal in Women

Abstract

In the present study, we introduce clitoral photoplethysmography as an instrument to assess clitoral blood volume (CBV). In research on female sexual functioning, vaginal pulse amplitude (VPA), as measured using vaginal photoplethysmography, has been used extensively as a measure of vaginal vasocongestion. Measurement of clitoral blood flow has thus far been problematic, mainly because of methodological constraints. To demonstrate that CBV is a valuable, easy to use complementary measure for the female sexual response, offering additional information to the VPA. Thirty women with and without female sexual dysfunction (FSD) watched neutral and erotic film clips. At the end of the erotic clip, the session was interrupted to induce inhibition of the sexual response. Another neutral clip followed the interruption. VPA and CBV were measured simultaneously, as well as skin conductance levels (SCLs), to assess the amount of sympathetic activity. VPA, CBV, SCL. For both FSD and non-FSD women, VPA and CBV increased when sexually explicit material was presented. Changes in skin conductance significantly predicted changes in CBV (b = -0.61, t[27] = -3.88, P < 0.001), but not in VPA. A large increase in sympathetic activity was accompanied by a large decrease in CBV. Furthermore, a large increase in CBV at the end of the erotic film clip presentation, as compared with the neutral clip, was accompanied by a relatively small increase in VPA (b = -0.39, t[29] = -2.25, P < 0.033). CBV is a valid and sensitive tool to measure the female genital response. In the present study, it was particularly useful in investigating sexual inhibition, when used in combination with SCL. Furthermore, high CBV appeared to inhibit VPA, suggesting that VPA reflects an automatic preparatory response rather than genital arousal per se.