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.

Reward Sensitivity and Waiting Impulsivity: Shift towards Reward Valuation away from Action Control.

Background: Impulsivity and reward expectancy are commonly interrelated. Waiting impulsivity, measured using the rodent 5-Choice Serial Reaction Time task, predicts compulsive cocaine seeking and sign (or cue) tracking. Here, we assess human waiting impulsivity using a novel translational task, the 4-Choice Serial Reaction Time task, and the relationship with reward cues. Methods: Healthy volunteers (n=29) performed the monetary incentive delay task as a functional MRI study where subjects observe a cue predicting reward (cue) and wait to respond for high (£5), low (£1), or no reward. Waiting impulsivity was tested with the 4-Choice Serial Reaction Time task. Results: For high reward prospects (£5, no reward), greater waiting impulsivity on the 4-CSRT correlated with greater medial orbitofrontal cortex and lower supplementary motor area activity to cues. In response to high reward cues, greater waiting impulsivity was associated with greater subthalamic nucleus connectivity with orbitofrontal cortex and greater subgenual cingulate connectivity with anterior insula, but decreased connectivity with regions implicated in action selection and preparation. Conclusion: These findings highlight a shift towards regions implicated in reward valuation and a shift towards compulsivity away from higher level motor preparation and action selection and response. We highlight the role of reward sensitivity and impulsivity, mechanisms potentially linking human waiting impulsivity with incentive approach and compulsivity, theories highly relevant to disorders of addiction.

Fronto-striatal organization: Defining functional and microstructural substrates of behavioural flexibility.

Discrete yet overlapping frontal-striatal circuits mediate broadly dissociable cognitive and behavioural processes. Using a recently developed multi-echo resting-state functional MRI (magnetic resonance imaging) sequence with greatly enhanced signal compared to noise ratios, we map frontal cortical functional projections to the striatum and striatal projections through the direct and indirect basal ganglia circuit. We demonstrate distinct limbic (ventromedial prefrontal regions, ventral striatum - VS, ventral tegmental area - VTA), motor (supplementary motor areas - SMAs, putamen, substantia nigra) and cognitive (lateral prefrontal and caudate) functional connectivity. We confirm the functional nature of the cortico-striatal connections, demonstrating correlates of well-established goal-directed behaviour (involving medial orbitofrontal cortex - mOFC and VS), probabilistic reversal learning (lateral orbitofrontal cortex - lOFC and VS) and attentional shifting (dorsolateral prefrontal cortex - dlPFC and VS) while assessing habitual model-free (SMA and putamen) behaviours on an exploratory basis. We further use neurite orientation dispersion and density imaging (NODDI) to show that more goal-directed model-based learning (MBc) is also associated with higher mOFC neurite density and habitual model-free learning (MFc) implicates neurite complexity in the putamen. This data highlights similarities between a computational account of MFc and conventional measures of habit learning. We highlight the intrinsic functional and structural architecture of parallel systems of behavioural control.

Jumping the Gun: Mapping Neural Correlates of Waiting Impulsivity and Relevance Across Alcohol Misuse.

BACKGROUND: Why do we jump the gun or speak out of turn? Waiting impulsivity has a preclinical basis as a predictor for the development of addiction. Here, we mapped the intrinsic neural correlates of waiting and dissociated it from stopping, both fundamental mechanisms of behavioral control. METHODS: We used a recently developed translational task to assess premature responding and assess response inhibition using the stop signal task. We mapped the neural correlates in 55 healthy volunteers using a novel multi-echo resting-state functional magnetic resonance imaging sequence and analysis, which robustly boosts signal-to-noise ratio. We further assessed 32 young binge drinkers and 36 abstinent subjects with alcohol use disorders. RESULTS: Connectivity of limbic and motor cortical and striatal nodes mapped onto a mesial-lateral axis of the subthalamic nucleus. Waiting impulsivity was associated with lower connectivity of the subthalamic nucleus with ventral striatum and subgenual cingulate, regions similarly implicated in rodent lesion studies. This network was dissociable from fast reactive stopping involving hyperdirect connections of the pre-supplementary area and subthalamic nucleus. We further showed that binge drinkers, like those with alcohol use disorders, had elevated premature responding and emphasized the relevance of this subthalamic network across alcohol misuse. Using machine learning techniques we showed that subthalamic connectivity differentiates binge drinkers and individuals with alcohol use disorders from healthy volunteers. CONCLUSIONS: We highlight the translational and clinical relevance of dissociable functional systems of cortical, striatal, and hyperdirect connections with the subthalamic nucleus in modulating waiting and stopping and their importance across dimensions of alcohol misuse.

Enhanced attentional bias towards sexually explicit cues in individuals with and without compulsive sexual behaviours.

Compulsive sexual behaviour (CSB) is relatively common and has been associated with significant distress and psychosocial impairments. CSB has been conceptualized as either an impulse control disorder or a non-substance 'behavioural' addiction. Substance use disorders are commonly associated with attentional biases to drug cues which are believed to reflect processes of incentive salience. Here we assess male CSB subjects compared to age-matched male healthy controls using a dot probe task to assess attentional bias to sexually explicit cues. We show that compared to healthy volunteers, CSB subjects have enhanced attentional bias to explicit cues but not neutral cues particularly for early stimuli latency. Our findings suggest enhanced attentional bias to explicit cues possibly related to an early orienting attentional response. This finding dovetails with our recent observation that sexually explicit videos were associated with greater activity in a neural network similar to that observed in drug-cue-reactivity studies. Greater desire or wanting rather than liking was further associated with activity in this neural network. These studies together provide support for an incentive motivation theory of addiction underlying the aberrant response towards sexual cues in CSB.