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

The Empirical Status of the Preparation Hypothesis: Explicating Women's Genital Responses to Sexual Stimuli in the Laboratory

Research conducted in our laboratory and in other laboratories has revealed that (1) women's genital responses to visual and auditory stimuli are strongly affected by the presence of sexual cues, but that (2) specific sexual cues (e.g., gender of actors, the presence of sexual violence) often have little impact on the magnitude of the responses-that is, similar genital responses are observed to very different sexual stimuli. In addition, (3) women's genital responses do not strongly correspond with self-reported sexual partner and activity preferences, or (4) with self-reported sexual arousal during the presentation of sexual stimuli. Taken together, these facts represent a puzzle, especially considering that men's genital responses are highly affected by specific sexual cues and strongly correspond to stated preferences and self-reported sexual arousal. One hypothesis to explain female low cue-specificity and low concordance (relative to men) is the preparation hypothesis: Women's indiscriminate genital responses serve a protective function. That is, they do not indicate or necessarily promote sexual interest and motivation, but rather prepare the vaginal lumen for possible sexual activity and therefore prevent injuries that may occur as a result of penetration. We review evidence for and against this hypothesis. We conclude that the evidence is favorable but not entirely convincing, and more work is required to reach a firm conclusion. We offer directions for future research.

Use of the Bogus Pipeline Increases Sexual Concordance in Women But Not Men

Sexual concordance-the agreement between physiological (genital) and psychological (emotional) sexual arousal-is, on average, substantially lower in women than men. Following social role theory, the gender difference in sexual concordance may manifest because women and men are responding in a way that accommodates gender norms. We examined genital and self-reported sexual arousal in 47 women and 50 men using a condition known to discourage conformity to gender norms (i.e., a bogus pipeline paradigm). Participants reported their feelings of sexual arousal during a sexually explicit film, while their genital arousal (penile circumference, vaginal vasocongestion), heart rate (HR), and galvanic skin (GS) responses were recorded. Half of the participants were instructed that their self-reported sexual arousal was being monitored for veracity using their HR and GS responses (bogus pipeline condition; BPC); the remaining participants were told that these responses were recorded for a comprehensive record of sexual response (typical testing condition; TTC). Using multi-level modeling, we found that only women's sexual concordance was affected by testing condition; women in the BPC exhibited significantly higher sexual concordance than those in the TTC. Thus, we provide the first evidence that the gender difference in sexual concordance may at least partially result from social factors.

The Successful Measurement of Clitoral Pulse Amplitude Using a New Clitoral Photoplethysmograph: A Pilot Study

BACKGROUND

Although the clitoris is more sensitive to stimulation and its innervation more conducive to sensory feedback than the vagina, the field of sexual psychophysiology, which uses psychophysiological methods including genital response measures to study sexual arousal, relies heavily on the measurement of vaginal, rather than clitoral, pulse amplitude.

AIM

To develop and test a new clitoral photoplethysmograph for the measurement of clitoral pulse amplitude (CPA).

METHODS

2 versions of the new device, which differed in the orientation of the sensor and light source (parallel vs angled), were tested in 15 premenopausal, sexually functional women. Vaginal pulse amplitude (VPA) was assessed simultaneously. The women viewed a 3-minute erotic and an anxiety-inducing film segment with each clitoral sensor, interspersed with neutral video excerpts. In addition, they were asked to indicate their subjective level of sexual arousal during and after erotic video presentations.

OUTCOMES

The main outcome measures are CPA, VPA, and subjective sexual arousal.

RESULTS

The clitoral photoplethysmograph successfully detected CPA. The quality of the signals was best for the angled sensor. Main effects of the film and the interaction between the film and epoch were stronger for the clitoral than for the vaginal device. In addition, CPA followed more closely changes in intensity of sexual films than VPA. Within- and between-subject correlations between genital response and subjective sexual arousal were higher for the clitoral than for the vaginal device.

CLINICAL TRANSLATION

Comparison of CPA with other genital blood flow measures in clinical samples is indicated and may contribute to improved physiological assessments of sexual response in women.

STRENGTHS AND LIMITATIONS

Our sample was small and consisted of healthy volunteers. Future research could examine test-retest reliability, by including multiple recording sessions, and further explore the specificity of CPA by comparing sexual and non-sexual stimuli with positive valence.

CONCLUSION

This study presents the first instrument to successfully measure CPA. Mechelmans DJ, Sachtler WL, von Wiegand TE, et al. The Successful Measurement of Clitoral Pulse Amplitude Using a New Clitoral Photoplethysmograph: A Pilot Study. J Sex Med 2020;17:1118-1125.

Platelet-rich plasma administration to the lower anterior vaginal wall to improve female sexuality satisfaction

Objective:

To investigate the effect of platelet-rich plasma (PRP) injection to the lower one-third of the anterior vaginal wall on sexual function, orgasm, and genital perception in women with sexual dysfunction.

Materials and Methods:

Four sessions of PRP were administered to the anterior vaginal wall of 52 female patients with sexual dysfunction and orgasmic disorder [Female Sexual Function Index (FSFI) total score ≤26 orgasmic subdomain score ≤3.75]. Prior to the PRP administrations in each session, the FSFI validated in Turkish, the Female Genital Self-Image Scale (FGSIS), the Female Sexual Distress Scale-Revised (FSDS-R), and Rosenberg’s Self-Esteem Scale were used and in the final follow-up, and the Patient Global Impression of Improvement (PGI-I) was performed and the results were analyzed.

Results:

Following the application of the PRP, the total FSFI score was observed as 27.88±4.80 and the total score was 26 and above in 50% of the patients (p<0.001). Orgasm subdomain scores were found as 2.11±1.20 before the PRP treatment and 4.48±1.14 afterwards (p<0.001). A significant change was observed in all sub-domains after PRP and it was observed that this change started after the first administration (p<0.001). A statistically significant increase was determined in FGSIS genital perception scores, which was significant between the 1^st and 2^nd months (p<0.001). The FSDS-R scores showed a minimal increase in stress scores as the application number increased, but a statistically significant decrease was observed in the 4th administration (p<0.001). No statistically significant difference was found in Rosenberg Scale scores before and after treatment (p=0.389). High satisfaction was found in PGI-I scores.

Conclusion:

As a minimally invasive method, PRP administration to the distal anterior vaginal wall may improve female sexuality with high satisfaction.

The Relationship Between Sexual Functioning and Sexual Concordance in Women

Previous research using clinical samples has shown a positive relationship between women's sexual functioning and sexual concordance (i.e., agreement between genital and subjective sexual arousal). We further examined this relationship using concurrent measures of vaginal, clitoral, and subjective sexual responses in a community sample of women (N = 64, with 59.4% and 34.1% reporting sexual desire and/or arousal difficulties, respectively). Contrary to studies using clinical samples, sexual desire and arousal difficulties were associated with stronger sexual concordance, specifically when changes in subjective arousal predicted changes in genital responses. The subjective experience of arousal may be particularly important in influencing genital responses in women with sexual desire and arousal difficulties compared to unaffected women.

A review of infrared thermography as applied to human sexual psychophysiology

Infrared thermography (IRT) is a non-contact technique that permits mapping and analysis of the temperature of the body's skin surface. This method has been applied to sexual psychophysiology since the 1980s and its use has been expanding ever since, mainly because it provides several advantages over existing genital response measures. This article presents a review of experimental studies employing IRT to investigate human sexual arousal, with the aim of summarizing the available procedures and evidence so far and to identify important caveats in the literature. The studies reviewed support the feasibility and validity of IRT as a real-time physiological measure of sexual arousal but varied substantially regarding methodology and procedures. The results of this review underscore the value and validity of IRT in sexual psychophysiology and point at the critical need for the standardization of IRT protocols to accommodate the specific needs of applying this methodology to sexual physiology.

Genotype scores predict drug efficacy in subtypes of female sexual interest/arousal disorder: A double-blind, randomized, placebo-controlled cross-over trial

Attempts to develop a drug treatment for female sexual interest/arousal disorder have so far been guided by the principle of ‘one size fits all’, and have failed to acknowledge the complexity of female sexuality. Guided by personalized medicine, we designed two on-demand drugs targeting two distinct hypothesized causal mechanisms for this sexual disorder. The objective of this study was to design and test a novel procedure, based on genotyping, that predicts which of the two on-demand drugs will yield a positive treatment response. In a double-blind, randomized, placebo-controlled cross-over experiment, 139 women with female sexual interest/arousal disorder received three different on-demand drug-combination treatments during three 2-week periods: testosterone 0.5 mg + sildenafil 50 mg, testosterone 0.5 mg + buspirone 10 mg, and matching placebo. The primary endpoint was change in satisfactory sexual events. Subjects’ genetic profile was assessed using a microarray chip that measures 300,000 single-nucleotide polymorphisms. A preselection of single-nucleotide polymorphisms associated with genes that are shown to be involved in sexual behaviour were combined into a Phenotype Prediction Score. The Phenotype Prediction Score demarcation formula was developed and subsequently validated on separate data sets. Prediction of drug-responders with the Phenotype Prediction Score demarcation formula gave large effect sizes (d = 0.66 through 1.06) in the true drug-responders, and medium effect sizes (d = 0.51 and d = 0.47) in all patients (including identified double, and non-responders). Accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of the Phenotype Prediction Score demarcation formula were all between 0.78 and 0.79, and thus sufficient. The resulting Phenotype Prediction Score was validated and shown to effectively and reliably predict which women would benefit from which on-demand drug, and could therefore also be useful in clinical practice, as a companion diagnostic establishing the way to a true personalized medicine approach.

An International Urogynecological Association (IUGA)/International Continence Society (ICS) joint report on the terminology for the assessment of sexual health of women with pelvic floor dysfunction

AIMS

The terminology in current use for sexual function and dysfunction in women with pelvic floor disorders lacks uniformity, which leads to uncertainty, confusion, and unintended ambiguity. The terminology for the sexual health of women with pelvic floor dysfunction needs to be collated in a clinically-based consensus report.

METHODS

This report combines the input of members of the Standardization and Terminology Committees of two International Organizations, the International Urogynecological Association (IUGA), and the International Continence Society (ICS), assisted at intervals by many external referees. Internal and external review was developed to exhaustively examine each definition, with decision-making by collective opinion (consensus). Importantly, this report is not meant to replace, but rather complement current terminology used in other fields for female sexual health and to clarify terms specific to women with pelvic floor dysfunction.

RESULTS

A clinically based terminology report for sexual health in women with pelvic floor dysfunction encompassing over 100 separate definitions, has been developed. Key aims have been to make the terminology interpretable by practitioners, trainees, and researchers in female pelvic floor dysfunction. Interval review (5-10 years) is anticipated to keep the document updated and as widely acceptable as possible.

CONCLUSION

A consensus-based terminology report for female sexual health in women with pelvic floor dysfunction has been produced aimed at being a significant aid to clinical practice and a stimulus for research.

Optimizing assessment of sexual arousal in postmenopausal women using erotic film clips

OBJECTIVES

This study sought to assess sexual arousal in a subgroup of women by identifying erotic film clips that would be most mentally appealing and physically arousing to postmenopausal women.

STUDY DESIGN

By measuring levels of mental appeal and self-reported physical arousal using a bidirectional scale, we aimed to elucidate the clips that would best be utilized for sexual health research in the postmenopausal or over 50-year-old subpopulation.

RESULTS

Our results showed that postmenopausal women did not rate clips with older versus younger actors differently (p>0.05). The mean mental and mean physical scores were significantly correlated for both premenopausal subject ratings (r=0.69, p<0.001) and postmenopausal subject ratings (r=0.94, p<0.001).

CONCLUSIONS

Thus postmenopausal women do not show a preference for the age of actors used in erotic film clips; this knowledge is relevant for design of future sexual function research.

Controversies of Women’s Sexual Arousal and Desire

Abstract. The past three decades have seen an unprecedented increase in empirical research on women’s sexual response. In this review, we critically examine current controversies and assumptions associated with the nature of women’s sexual arousal and desire. We focus specifically on four assumptions: (1) the assumption that women should be aroused by stimuli that align with their stated preferences, (2) the assumption that women’s physiological and self-reported arousal should perfectly align, (3) the assumption that sexual desire precedes sexual arousal, and (4) the assumption that a single pharmaceutical compound will adequately restore women’s sexual response to her level of satisfaction. Engaging a gendered psychological framework for conceptualizing women’s sexuality, we emphasize the need for models of women’s sexual response to be sensitive to the sexed biological processes and gendered psychosocial factors that contribute to a woman’s unique sexual experience.

Single dose sublingual testosterone and oral sildenafil vs. a dual route/dual release fixed dose combination tablet: a pharmacokinetic comparison

AIM

The aim was to compare the pharmacokinetic profiles of two formulations of a combination drug product containing 0.5 mg testosterone and 50 mg sildenafil for female sexual interest/arousal disorder. The prototype (formulation 1) consists of a testosterone solution for sublingual administration and a sildenafil tablet that is administered 2.5 h later. The dual route/dual release fixed dose combination tablet (formulation 2) employs a sublingual and an oral route for systemic uptake. This tablet has an inner core of sildenafil with a polymeric time delay coating and an outer polymeric coating containing testosterone. It was designed to increase dosing practicality and decrease potential temporal non-adherence through circumventing the relatively complex temporal dosing scheme.

METHODS

Twelve healthy premenopausal subjects received both formulations randomly on separate days. Blood was sampled frequently to determine the pharmacokinetics of free testosterone, total testosterone, dihydrotestosterone, sildenafil and N-desmethyl-sildenafil.

RESULTS

Formulation 2 had a higher maximum concentration (Cmax ) for testosterone, 8.06 ng ml(-1) (95% confidence interval [CI] 6.84, 9.28) and higher area under the plasma concentration-time curve (AUC), 7.69 ng ml(-1)  h (95% CI 6.22, 9.16) than formulation 1, 5.66 ng ml(-1) (95% CI 4.63, 6.69) and 5.12 ng ml(-1)  h (95% CI 4.51, 5.73), respectively. Formulation 2 had a lower Cmax for sildenafil, 173 ng ml(-1) (95% CI 126, 220) and a lower AUC, 476 ng ml(-1)  h (95% CI 401, 551) than formulation 1, 268 ng ml(-1) (95% CI 188, 348) and 577 ng ml(-1)  h (95% CI 462, 692), respectively. Formulation 2 released sildenafil after 2.75 h (95% CI 2.40, 3.10).

CONCLUSIONS

The dual route/dual release fixed dose combination tablet fulfilled its design criteria and is considered suitable for further clinical testing.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

Female sexual interest/arousal disorder (FSIAD) is a significant problem impacting psychological well-being, but the pharmacotherapeutic options for this problem are lacking. The combined, on-demand, sublingual administration of low dose sublingual testosterone and oral administration of sildenafil is a novel pharmacotherapeutic option under development for FSIAD. In proof-of-concept trials, these compounds were successfully administered via different dosage forms (sublingual and oral) at different time points (separated by 2.5 h) because of their markedly different pharmacokinetic-pharmacodynamic profiles. For future larger scale studies and the clinical practice, this raises obvious adherence issues.

WHAT THIS STUDY ADDS

A newly developed dual route/dual release fixed dose combination tablet containing testosterone and sildenafil mimics the pharmacokinetic profile of these components when they are administered as different dosage forms, 2.5 h apart. This combination tablet is a suitable final pharmaceutical drug product that will be used in future studies.

The Clitoral Photoplethysmograph: A Pilot Study Examining Discriminant and Convergent Validity

INTRODUCTION

The clitoral photoplethysmograph (CPP) is a relatively new device used to measure changes in clitoral blood volume (CBV); however, its construct validity has not yet been evaluated.

AIM

To evaluate the discriminant and convergent validity of the CPP. For discriminant validity, CBV responses should differ between sexual and nonsexual emotional films if the CPP accurately assesses clitoral vasocongestion associated with sexual arousal; for convergent validity, CBV responses should significantly correlate with subjective reports of sexual arousal.

METHODS

Twenty women (M age = 21.2 years, SD = 3.4) watched neutral, anxiety-inducing, exhilarating, and sexual (female-male sex) audiovisual stimuli while their genital responses were measured simultaneously using vaginal and clitoral photoplethysmographs and CPPs. Most of these participants continuously reported sexual arousal throughout each stimulus (n = 16), and all reported their sexual and nonsexual affect before and after each stimulus; subjective responses were recorded via button presses using a keypad.

MAIN OUTCOME MEASURES

Vaginal pulse amplitude (VPA), CBV, and self-reported sexual arousal and nonsexual affect were used as main outcome measures.

RESULTS

CBV demonstrated both discriminant and convergent validity. CBV responses were similar to VPA responses and self-reported sexual arousal; all responses differed significantly as a function of stimulus content, with the sexual stimulus eliciting greater relative changes than nonsexual stimuli. CBV, but not VPA, was significantly (negatively) correlated with continuous self-reported sexual arousal during the shorter sexual stimulus. CBV was significantly negatively correlated with VPA for the shorter sexual stimulus.

CONCLUSION

CBV may be a valid measure of women's genital sexual arousal that provides complementary information to VPA and correlates with self-reported sexual arousal. Given our relatively small sample size, and that this is among the first research to use the CPP, the current findings must be replicated. More research using the CPP and other devices is required for a more comprehensive description of women's physiological sexual arousal.

Devices and Methods to Measure Female Sexual Arousal

INTRODUCTION

Multiple methods and devices are available for the assessment of female sexual response, each with strengths and limitations that can impact interpretation of research results. As such, it is important to have an understanding of available methodologies and instruments.

AIM

To review recent literature on the measurement of female sexual response, and to describe the methods and devices, and their strengths and limitations.

METHODS

A literature review was performed regarding methodology and instruments used to quantify female sexual response.

MAIN OUTCOME MEASURES

The description of currently available instruments and methods to quantify sexual response in women.

RESULTS

Methodologies used to examine female sexual arousal employ a variety of stimuli and instruments to elicit and record sexual response. The variation in research designs across studies highlights the importance of understanding (i) how sexual response is elicited in studies; (ii) what kinds of experimental designs are available for assessing sexual psychophysiology; and (iii) the various types of instrumentation used to collect data.

CONCLUSIONS

The physiological and self-reported measurement of female sexual response is crucial to our understanding of the mechanisms and factors involved with healthy sexual functioning. As such, it is important to understand the strengths and limitations associated with different stimuli, research designs, and instruments. Kukkonen TM. Devices and methods to measure female sexual arousal.

Assessment of Introital Lubrication

Vaginal vasocongestion and lubrication serve to prepare the vaginal lumen for sexual activity. Lubrication is important for sexual functioning and difficulties with lubrication are one of the most commonly reported symptoms of sexual dysfunction. Few studies have empirically examined how vasocongestion and lubrication relate to one another and there are currently no well-established measures of lubrication. In this study, we designed and tested a simple method to assess lubrication at the vaginal introitus in 19 healthy women, using litmus test strips. We examined the relationship between lubrication and vaginal vasocongestion (measured with a photoplethysmograph) when elicited by audiovisual sexual stimuli (male-female sexual interactions). Lubrication was elicited by the sexual stimuli and was strongly correlated with reports of sexual arousal. Unexpectedly, lubrication was not correlated with vasocongestion, even though the latter was also elicited by the sexual stimuli. We discuss the implications of these findings for informing our understanding of the female sexual response and the potential clinical and scientific utility of this new measure.

Beyond the G-spot: clitourethrovaginal complex anatomy in female orgasm

The search for the legendary, highly erogenous vaginal region, the Gräfenberg spot (G-spot), has produced important data, substantially improving understanding of the complex anatomy and physiology of sexual responses in women. Modern imaging techniques have enabled visualization of dynamic interactions of female genitals during self-sexual stimulation or coitus. Although no single structure consistent with a distinct G-spot has been identified, the vagina is not a passive organ but a highly dynamic structure with an active role in sexual arousal and intercourse. The anatomical relationships and dynamic interactions between the clitoris, urethra, and anterior vaginal wall have led to the concept of a clitourethrovaginal (CUV) complex, defining a variable, multifaceted morphofunctional area that, when properly stimulated during penetration, could induce orgasmic responses. Knowledge of the anatomy and physiology of the CUV complex might help to avoid damage to its neural, muscular, and vascular components during urological and gynaecological surgical procedures.

The pharmacology of the human female orgasm - its biological and physiological backgrounds

The female orgasm has been examined over the years by numerous scientific disciplines yet it still has many secrets to be disclosed. Because its physiology, especially its neurophysiology, is sparingly understood its pharmacology is necessarily limited based mainly on the side effects of drugs. Few published studies have used a placebo group as controls. The paucity of focussed studies is well illustrated by the fact that there still is no approved medication to treat female orgasmic dysfunction. The present brief overview examines the most important aspects of its biology and especially its physiology highlighting the many questions that need answering if we are to have a comprehensive pharmacology of the female orgasm.

Phosphodiesterase type 5 inhibitors and female sexual response: faulty protocols or paradigms?

INTRODUCTION

Phosphodiesterase type 5 inhibitors (PDE5), such as sildenafil, tadalafil, and vardenafil, have revolutionized the treatment of erectile dysfunction. Few successes, in contrast, have been reported for the use of these agents in treatment of sexual arousal problems in women.

AIM

To review research examining efficacy of PDE5 in women, critique the methods and models employed, and integrate the findings within a broader, gender-specific understanding of female sexual response.

METHODS

A conceptual and methodological review of all published studies examining PDE5 efficacy in female samples.

MAIN OUTCOME MEASURES

Study methods, populations, outcome measures, study results.

RESULTS

A total of 16 studies were reviewed. Studies using self-reported measures of sexual functioning showed mixed results whereas studies examining physiological effects of PDE5 on genital vasocongestion consistently report significant effects on genital sexual response.

CONCLUSIONS

The lack of efficacy of PDE5 treatment in women is likely attributable to gender differences in the concordance between physiological and psychological components of sexual response. Discordance between genital and subjective measures of sexual response in women may be augmented by PDE5 effects on genital vasocongestion in some populations, rendering successful treatment unlikely via pharmacological treatment alone.