Sensation-seeking: electrodermal and behavioral effects of stimulus content and intensity

Although a number of studies support an arousal theory interpretation of differential sensation-seeking behavior, the conditions under which arousal correlates of this personality dimension are manifest is as yet unclear. Both theory and research suggest that among the external factors affecting the differential arousal response are stimulus relevance and stimulus intensity. The present study assessed the impact of these factors on both psychophysiological and behavioral responses. Subjects were preselected to represent the extremes of the sensation-seeking dimension, then exposed to auditory and visual presentations of a series of sexual and aggressive stimuli of systematically varied intensity. High sensation seekers gave larger amplitude SCRs to violent stimuli and larger initial responses to sexual stimuli presented visually, while verbal response intensities showed an opposite pattern. Overall, results provided support for an arousal theory interpretation of sensation-seeking, but suggested that the probability and magnitude of group differences is a somewhat complex function of stimulus intensity, stimulus modality, and perhaps other factors not yet assessed.     

Facial Electromyography: A Measure of Affective Processes During Sexual Arousal

Forty female volunteers participated in a study to investigate whether facial EMGs could be used as measures of affect during sexual arousal. Audiotaped narratives were used to induce the following affect-sexual states: 1) pleasant affect + sexual arousal, 2) unpleasant affect + sexual arousal, 3) pleasant affect + no sexual arousal, and 4) unpleasant affect + no sexual arousal. EMG activity was recorded bilaterally from the corrugator and zygomatic muscle regions. Corrugator muscle activity was significantly greater in response to the unpleasant stimulus conditions. This relationship held for both the non-sexual and sexual conditions, suggesting that corrugator muscle activity may provide a reliable index of negative affect during sexual arousal. Zygomatic activity was significantly greater during the sexual as compared to the non-sexual stimuli, but did not increase as a function of pleasant affect. Greater left than right corrugator muscle activity was observed in response to the sexual stimuli. Left muscle superiority was also noted for zygomatic muscle activity, in response to the sexual unpleasant stimulus. Issues related to the interpretation of lateralized muscle activity are discussed.     

The effect of visual sexual content on the event-related potential

In the present study we investigated the effect of emotional valence and arousal value of non-erotic visual stimuli on event-related potentials. We also directly compared the effects of erotic and non-erotic stimuli of comparable valence and arousal levels. Sixteen sexually functional heterosexual males rated 150 computer screen pictures, selected from the International Affective Picture System, representing five stimulus types differing along dimensions of emotional valence and arousal, and erotic vs. non-erotic content. A positive deflection of the ERP between 300 and 500ms after stimulus onset (P300) was found to be sensitive to stimulus differences, with positive valence and high arousal resulting in larger P300. Furthermore, the positive slow wave (PSW) between 500 and 750ms revealed additive effects of valence and arousal value. High arousal and positive valence of the stimuli resulted in larger PSW. Importantly, an interaction effect was absent here. In addition, sexual content led to a larger P300 and PSW than expected on the basis of a mere additive contribution of high arousal and positive valence.     

Men and women differ in amygdala response to visual sexual stimuli

Men are generally more interested in and responsive to visual sexually arousing stimuli than are women. Here we used functional magnetic resonance imaging (fMRI) to show that the amygdala and hypothalamus are more strongly activated in men than in women when viewing identical sexual stimuli. This was true even when women reported greater arousal. Sex differences were specific to the sexual nature of the stimuli, were restricted primarily to limbic regions, and were larger in the left amygdala than the right amygdala. Men and women showed similar activation patterns across multiple brain regions, including ventral striatal regions involved in reward. Our findings indicate that the amygdala mediates sex differences in responsiveness to appetitive and biologically salient stimuli; the human amygdala may also mediate the reportedly greater role of visual stimuli in male sexual behavior, paralleling prior animal findings.     

Stimulus rise time, intensity and the elicitation of unconditioned cardiac and electrodermal responses.

In recent discussions on the differentiation of orienting, startle and defense responses, the importance of stimulus rise time for the elicitation of different cardiac response patterns was re-emphasized. Especially, it has been claimed that phasic accelerative heart rate (HR) responses-interpreted as indicators of startle-might not only be evoked by auditory stimuli with instantaneous rise times and high intensities, but also by low to moderate stimulus intensities with sudden onsets. The present study examined this question by manipulating rise time (instantaneous vs. 50 ms) and intensity (60 vs. 95 dB). Subjects (N = 120) were randomly assigned to one of the four independent groups. They performed a habituation experiment in which 12 tones of 1000 Hz with a constant interstimulus interval of 90 s were presented. On trial 13, a change in rise time was introduced by reversing the rise time condition in each group (i.e., from instantaneous to 50 ms and vice versa). Examination of HR changes across 4 poststimulus seconds, of maximal HR deceleration and acceleration, as well as examination of magnitude of skin conductance responses (SCRs) indicated clear intensity effects. Rise time, on the other hand, had no effects on HR and SC that could be interpreted as indicative of startle. Thus, it could neither be observed that instantaneous rise time led to stronger accelerative HR responses nor that the combination of instantaneous rise time and high intensity elicited anything but a dominant accelerative response pattern. These findings were also obtained when the first four trials were analyzed separately. As a consequence of stimulus change, larger SCRs as well as larger decelerative HR responses were observed without, however, being affected by the direction of the change in rise time. In sum, the present study suggests that the role attributed to rise time with respect to eliciting qualitatively different cardiac response patterns has been exaggerated. The consequences for the differentiation of different unconditioned responses are briefly addressed.     

Psychoendocrine response to sexual arousal in human males

The hypothesis is tested that luteinizing hormone (LH) and follicle stimulating hormone (FSH( may be released from the anterior pituitary in response to a psychological state of sexual arousal. LH levels in 10 male volunteers were found to be higher after viewing a sexually arousing film than after a control film. The magnitude of LH response was found to be positively correlated with the subjective evaluation of sexual arousal. FSH levels tended in the same direction bu the predominant and unexpected finding for this hormone was that levels were consistently lower during the first session, when anxiety was high, and higher during the second session, when anxiety was less, whether control or stimulus film had been shown. This study is analogous to those demonstrating the responsiveness of other anterior pituitary hormones to specific psychological states.     

Bilateral Asymmetry of Skin Conductance Responses During Auditory and Visual Tasks

Bilateral skin conductance (SC) was recorded while dextral subjects engaged in tasks designed to differentially engage the right (RH) and left (LH) hemispheres. Subjects compared strings of speech sounds (LH) and musical chords (RH). They also decided whether written words rhymed (LH) and viewed pictures of faces in a continuous recognition paradigm (RH). SCRs in the right hand were larger during the chords task than the syllables task. The left hand did not differ for the two stimuli. In the visual experiment a comparable effect was obtained in males only. SCRs in the left hand were larger for rhymes than faces; the right hand did not differentiate between stimuli. Sex differences in laterality are considered. Subjects who were more equally balanced in awareness of the two sides of their bodies and subjects with familial sinistrals were more likely to show task appropriate SC changes. Using rote repetition and visual imagery as mnemonics did not affect SC asymmetries.     

The effects of beta-endorphin infusions into the amygdala on visual and olfactory sensory processing during sexual behaviour in the male rat.

Sexually experienced male rats infused bilaterally into the amygdala with 60 pmol beta-endorphin show decreased rate of precopulatory investigation of the female and delayed intromission latency, but copulation is left unaltered. Such males are still able to discriminate between the odours of bedding from receptive and unreceptive females, demonstrating that beta-endorphin does not impair the ability to detect sexually relevant odours. Preventing visual cues emitted by females during proceptive behaviour (by treating them with haloperidol) delayed intromission latency but had no effect on preintromission investigation. Intra-amygdaloid beta-endorphin exacerbated the effects of this treatment on the intromission latency. Inducing anosmia in males (by applying zinc sulphate solution to the olfactory mucosa) decreased their anogenital investigation and delayed their intromission latency. These effects were not enhanced by intra-amygdaloid beta-endorphin. Allowing males to investigate and initiate the first intromission prior to intra-amygdaloid infusion had no effects on subsequent intromissions. However, if following an intromission with one female and an infusion of beta-endorphin, the male was presented with an unfamiliar female then the effects of intra-amygdaloid beta-endorphin on investigation and intromission returned. These results suggest that beta-endorphin in the amygdala interferes with the processing of female-specific olfactory information. Without this processed information, classification of the female as a sexual stimulus may be impeded and thus sexual arousal delayed.     

Event-related skin conductance responses to musical emotions in humans

While the reasons underlying musical emotions are unclear, music is nevertheless a powerful elicitor of emotion, and as such, may induce autonomic nervous system responses. One typical measure of this neural pathway is the skin conductance response (SCR). This response generally depends upon stimulus arousal, one of the two motivational determinants of emotion. The objective of the present study was to verify whether emotional reactions to music elicit such event-related autonomic responses. To this aim, four musical emotions varying in arousal were employed: fear, happiness, sadness and peacefulness. SCRs were found to be greater with the two more stimulating emotions, fear and happiness, as compared to the two more relaxing emotions, sadness and peacefulness (P<0.05). In addition, subjects' ratings of the emotional clarity for each excerpt did not parallel the corresponding SCRs magnitudes. The results show that SCRs can be evoked and modulated by musical emotional arousal, but are not sensitive to emotional clarity. While several studies have been performed with visual scenes and environmental sounds, the present study brings similar evidence from the musical domain.     

Asymmetric eeg changes as method actors generated emotions

Nine method actors recalled personal experiences to create emotional states of sexual arousal or depression. Electroencephalographic (EEG) data recorded from left and right frontal, central, parietal and occipital locations were spectrally analyzed for power in each major frequency band and for coherence among all pairs of channels. Contrasts between the emotion conditions showed less alpha power (greater activation) over the right hemisphere for sexual arousal than for depression. Analysis of coherence topography showed higher coherence in right central and posterior regions during the sexual arousal condition. These data are consistent with previous evidence of right hemisphere contribution to sexual arousal and suggest further that asymmetric patterns of brain activity may be associated with specific emotional states.     

Hemispheric Asymmetry and Human Classical Conditioning to Verbal and Non-Verbal Visual CSs

A new paradigm called “the dichoplic acquisition paradigm” was developed to study Ihc effects of hemispheric asymmetry on classical etcctrodcrmal conditioning. The paradigm involves three phases: 1) A habituation phase where two different color-words written in two incongruent colors are tachistoscopically displayed bilaterally to the visual half-fields left and right of center fixation; 2) An acquisition phase, wherein the display is followed by a 105dB white noise on each trial; and 3) An extinction phase, where each of the four CS cues (two color-words and two colors) are separately presented bilaterally for simultaneous input to both hemispheres. Here the color-words are now presented in grey against a black background, and the colors as color-bars against the same background. A control group had no UCS presentations. Bilateral skin conductance responses (SCRs) of right-handed males were used to evaluate conditioning. Conditioning to the CS color-word previously presented in the right half-field (i.e. initial left-hemisphere input) during acquisition led to larger SCRs during extinction, than the color-word previously presented in the left half-held (i.e. initial right-hemisphere input). In contrast, the CS color cue previously presented in the left half-field during acquisition resulted in larger SCRs during the first extinction trial, than the CS color cue previously presented in the right half-field. Thus, the present experiment revealed effects of hemispheric asymmetry on human electrodermal conditioning.     

Modulation of spinal reflexes by aversive and sexually appetitive stimuli

In this study, modulation of spinal tendinous (T) reflexes by sexual stimulation was investigated. T reflexes are augmented in states of appetitive and defensive action and modified by differences in arousal intensity. Reflexes were expected to be facilitated by both pleasant (sexual) and unpleasant (anxiety) stimuli. Subjects were exposed to a sexual, an anxiety-inducing, a sexually threatening, and a neutral film excerpt. Genital arousal, emotional experience, subjective action tendencies, and T reflexes were monitored. Self-report and genital data confirmed the affective states as intended. T reflex amplitude significantly increased during viewing of emotionally arousing film excerpts as compared with a neutral film excerpt. T reflexes were facilitated by the sex stimulus to the same extent as by the anxiety and sexual threat stimuli. The results support the view of sexual arousal as an emotional state, generating sex-specific autonomic and general somatic motor system responses, which prepare the organism for action.     

Does dorsolateral prefrontal cortex (DLPFC) activation return to baseline when sexual stimuli cease?: The role of DLPFC in visual sexual stimulation

A fundamental question in human sexuality regards the neural substrate underlying sexually-arousing representations. Lesion and neuroimaging studies suggest that dorsolateral pre-frontal cortex (DLPFC) plays an important role in regulating the processing of visual sexual stimulation. The aim of this Functional Near-Infrared Spectroscopy (fNIRS) study was to explore DLPFC structures involved in the processing of erotic and non-sexual films. fNIRS was used to image the evoked-cerebral blood oxygenation (CBO) response in 15 male and 15 female subjects. Our hypothesis is that a sexual stimulus would produce DLPFC activation during the period of direct stimulus perception ("on" period), and that this activation would continue after stimulus cessation ("off" period). A new paradigm was used to measure the relative oxygenated hemoglobin (oxyHb) concentrations in DLPFC while subjects viewed the two selected stimuli (Roman orgy and a non-sexual film clip), and also immediately following stimulus cessation. Viewing of the non-sexual stimulus produced no overshoot in DLPFC, whereas exposure to the erotic stimulus produced rapidly ascendant overshoot, which became even more pronounced following stimulus cessation. We also report on gender differences in the timing and intensity of DLPFC activation in response to a sexually explicit visual stimulus. We found evidence indicating that men experience greater and more rapid sexual arousal when exposed to erotic stimuli than do women. Our results point out that self-regulation of DLPFC activation is modulated by subjective arousal and that cognitive appraisal of the sexual stimulus (valence) plays a secondary role in this regulation.     

Autonomic responding to aversive words without conscious valence discrimination.

A growing body of data suggests that the emotional dimension of a stimulus can be processed without conscious identification of the stimulus. The arousal system could be activated by unrecognised biologically significant stimuli through simple physical stimulus features related to threat, without any evaluation of the meaning of the stimulus. However, unconscious processing of emotionally laden words cannot rely only on perceptual features but must include some analysis of symbolic meaning. The first aim of the present study was to assess whether masked (unrecognised) aversive words can elicit enhanced skin conductance responses (SCRs), a major autonomic index of emotional arousal, in normal participants. Our second aim was to determine whether any autonomic activation related to affective value of words is independent from access of this value to consciousness. Thus, the presentation duration of masked aversive and neutral words was determined, for each participant, in such a way that (1) identification was precluded, (2) valence discrimination was at chance, as indicated by performance in a forced-choice two-alternative task and by confidence ratings of the responses, and (3) emotional and neutral words were not detected differentially. SCRs were recorded during masked and unmasked presentations of both types of word. SCRs elicited by unmasked words, and also by masked words, were of greater magnitude when the words were emotional than when they were neutral. Consequently, in normal participants, autonomic activation can be a discriminative marker of the affective dimension of unrecognised verbal material in the absence of conscious valence identification.     

Examining gender specificity of sexual response with concurrent thermography and plethysmography

Men's genital responses are significantly greater to sexual stimuli of their preferred gender compared to their nonpreferred gender (gender‐specific), whereas androphilic (i.e., sexually attracted to men) women's genital responses are similar to sexual stimuli depicting either women or men (gender‐nonspecific). This gendered pattern of genital response has only been demonstrated using vaginal photoplethysmography (VPP) in women and primarily penile plethysmography (PPG) in men. These measures assess different aspects of genital vasocongestion, thereby limiting comparisons between genders. Thermography is a newer sexual psychophysiology methodology that measures genital vasocongestion via temperature change and is better suited to assess sexual response between genders because the dependent measure, change in genital temperature, is similar for women and men. Further, previous studies have assessed gender specificity of sexual response across relatively short sexual stimuli, allowing only the examination of initial phases of sexual response. We examined gender specificity of sexual arousal by measuring women's and men's genital responses to lengthier stimuli with concurrent thermography and VPP/PPG. Gynephilic men (i.e., sexually attracted to women; n = 27) and androphilic women (n = 28) viewed 10‐min films depicting men masturbating, women masturbating, and a nonsexual film, and reported feelings of sexual arousal while genital responses were assessed. Across measures, men's sexual responses were gender‐specific and women's responses were gender‐nonspecific, indicating that the gender difference in gender specificity of arousal is robust to methodology and stimulus duration. These findings replicate previous research, extend knowledge of gendered sexual response, and highlight the utility of multimethod approaches in sexual psychophysiology.     

The relationship of male self-report of rape supportive attitudes,sexual fantasy,social desirability and physiological arousal to sexually coercive stimuli

Studies have supported the finding that sexually coercive behavior exists between males and females on college campuses and that when women say “no” to sexual behavior, men do not believe them. This study utilized penile plethysmography to investigate male sexual arousal to rape myth scenarios in a college population. The scenarios portrayed a woman who said “no” to sexually coercive intercourse behavior by a male. Results indicated that a low level of social desirability, sexual fantasies involving group sexual activity, as well as hurting and being hurt by a partner were associated with greater levels of physiological responding to coercive stimuli. Supportive attitudes about rape showed no relationship with physiological responding, yet did correlate with the sexual fantasy of being hurt by a partner, which was itself related to increased sexual arousal to sexually coercive audio stimuli. © 1997 John Wiley & Sons, Inc. J Clin Psychol 53: 935–942, 1997     

Persistent genital arousal disorder associated with functional hyperconnectivity of an epileptic focus

Persistent Genital Arousal Disorder (PGAD) refers to the experience of persistent sensations of genital arousal that are felt to be unprovoked, intrusive and unrelieved by one or several orgasms. It is often mistaken for hypersexuality since PGAD often results in a high frequency of sexual behaviour. At present little is known with certainty about the etiology of this condition. We described a woman with typical PGAD symptoms and orgasmic seizures that we found to be related to a specific epileptic focus. We performed a EEG/MEG and fMRI spontaneous activity study during genital arousal symptoms and after the chronic administration of 300 mg/day of topiramate. From MEG data an epileptic focus was localized in the left posterior insular gyrus (LPIG). FMRI data evidenced that sexual excitation symptoms with PGAD could be correlated with an increased functional connectivity (FC) between different brain areas: LPIG (epileptic focus), left middle frontal gyrus, left inferior and superior temporal gyrus and left inferior parietal lobe. The reduction of the FC observed after antiepileptic therapy was more marked in the left than in the right hemisphere in agreement with the lateralization identified by MEG results. Treatment completely abolished PGAD symptoms and functional hyperconnectivity. The functional hyperconnectivity found in the neuronal network including the epileptic focus could suggest a possible central mechanism for PGAD.     

Male bisexual arousal: A matter of curiosity?

Conflicting evidence exists regarding whether bisexual-identified men are sexually aroused to both men and women. We hypothesized that a distinct characteristic, level of curiosity about sexually diverse acts, distinguishes bisexual-identified men with and without bisexual arousal. Study 1 assessed men's (n = 277) sexual arousal via pupil dilation to male and female sexual stimuli. Bisexual men were, on average, higher in their sexual curiosity than other men. Despite this general difference, only bisexual-identified men with elevated sexual curiosity showed bisexual arousal. Those lower in curiosity had responses resembling those of homosexual men. Study 2 assessed men's (n = 72) sexual arousal via genital responses and replicated findings of Study 1. Study 3 provided information on the validity on our measure of sexual curiosity by relating it to general curiosity and sexual sensation seeking (n = 83). Based on their sexual arousal and personality, at least two groups of men identify as bisexual.     

Determinants of subjective experience of sexual arousal in women: Feedback from genital arousal and erotic stimulus content

Sixty-two women participated in a study designed to explore the association between gential and subjective sexual arousal. Four stimulus conditions were created, designed to evoke differential patterns of genital arousal over time. Subjects were instructed to report sensations in their genitalia while being exposed to the same erotic stimulus on repeated trials or to a series of varying erotic stimuli. Detection of genital arousal was facilitated by the occurrence of changes in genital arousal over trials. That is, genital and subjective sexual arousal were linearly related in conditions that resulted in large differences in genital arousal over trails, whereas such a relation was absent in conditions in which genital arousal levels remained relatively constant. In women, peripheral feedback from consciously detected genital arousal seems to be a relatively unimportant determinant of subjective sexual arousal.