Ventral striatum activity when watching preferred pornographic pictures is correlated with symptoms of Internet pornography addiction
Introduction
Internet pornography addiction (IPA) is considered one specific type of Internet addiction (Griffiths, 2012, Young, 2008), although currently not included in international classification systems. Watching pornographic material on the Internet is the most frequently used form of cybersex, at least in males (Paul and Shim, 2008, Shaughnessy et al., 2011). Previous studies showed similarities between IPA and other behavioral addictions, e.g. higher cue-reactivity and craving on a behavioral level (Brand et al., 2011, Laier and Brand, 2014, Laier et al., 2013). Neuroimaging studies on patients with Internet gaming disorder revealed activity in the ventral striatum (e.g., Ko et al., 2009, Kuss and Griffiths, 2012), known to participate in reward anticipation and craving (Kühn and Gallinat, 2011, Robinson and Berridge, 2000), when subjects were confronted with addiction-related stimuli (cf., Brand et al., 2014b, Stippekohl et al., 2010). Also, some recent neuroimaging studies with hypersexual males identified ventral striatum activity when participants watched explicit sexual stimuli compared to non-explicit sexual/erotic material (Voon et al., 2014). It has also been reported that activity in the left putamen while watching sexual pictures compared to non-sexual pictures was positively correlated with hours spent for pornography consumption on the Internet (Kühn and Gallinat, 2014). One theoretical idea that might explain why some people experience a loss of control over their Internet pornography consumption is that they search material fitting perfectly with their individual sexual fantasies and desires. Consistent with this, it has been suggested that those users who have certain sexual fantasies, which can be satisfied by Internet pornography better than in real world, are at-risk for developing an addictive pornography use (Cooper et al., 2000, Cooper et al., 2004). Given that sexual stimuli are considered naturally rewarding (Georgiadis and Kringelbach, 2012), the results of the aforementioned neuroimaging studies (Kühn and Gallinat, 2014, Voon et al., 2014) may also reflect anticipation of sexual arousal in general because they used pornographic material in contrast to erotic (but not explicit pornographic) or neutral material. Based on these inspiring findings, it seems very important to investigate neural responses to pornographic material that is consistent with subjects' sexual preferences compared to pornographic material, which is less sexually arousing though also explicitly pornographic. This means that by investigating the hypotheses by Cooper et al., 2000, Cooper et al., 2004, it would be interesting to study neural activity related to preferred pornographic material in contrast to non-preferred but also pornographic material. This would also determine whether neural responses to pornographic material reflect a general activation to sexual stimuli as a natural reward category (Georgiadis and Kringelbach, 2012) or a specific activation to sexual stimuli that are subjectively arousing. This is important to investigate, since current models on the development and maintenance of IPA (Laier and Brand, 2014) postulate that one key factor of IPA is that subjects find easily explicit pornographic material on the Internet that fits with their personal desires and preferences. This would in turn result in high experienced gratification, which is reinforcing and should accelerate the development of IPA (Young, 2008, Young et al., 2000).
Following this line of argumentation, ventral striatum responses should be stronger to preferred compared to non-preferred pornographic stimuli. Ventral striatum responses to preferred vs. non-preferred pornographic material should also correlate positively with symptom severity of IPA, as such correlations have been shown on a subjective and behavioral level (Brand et al., 2011, Laier and Brand, 2014, Laier et al., 2013, Laier et al., 2014b). The current study investigated these hypotheses with functional magnetic resonance imaging (fMRI) in male heterosexual participants, using a picture paradigm with explicit pornographic material that was subjectively preferred (e.g., showing male–female sexual interaction) as well as material that was non-preferred (e.g., showing male–male sexual interaction) (Laier et al., 2013). We have also included scales assessing depression and interpersonal sensitivity, because these two psychopathological symptoms are considered main correlates of Internet addiction (see meta-analysis by Ho et al., 2014) as well as vulnerability factors in recent models on Internet addiction in general (Brand et al., 2014b), and IPA or cybersex addiction in particular (Laier and Brand, 2014). We also included further measures for hypersexual behavior, sexual excitation, and socio-sexual contacts, because these measures have also been considered important in previous studies (Kühn and Gallinat, 2014, Voon et al., 2014) and theoretical models on IPA (Laier and Brand, 2014).
Section snippets
Participants
We investigated 20 heterosexual males. One participant had to be excluded from fMRI analyses due to strong head movements during the scanning. The final sample consisted of 19 participants (mean age = 25.05, SD = 1.43 years). All participants were right-handed.
We advertised for heterosexual males of legal age and indicated that participating would include viewing explicit pornographic pictures of sexual practices between adults. Sexual orientation was assessed with a nominal scale asking
Scores in the questionnaires and behavioral results in the fMRI paradigm
The scores in the questionnaires are shown in Table 1. Although the mean score in the s-IATsex was moderate, there was a considerable variance indicating that the sample consisted of subjects using Internet pornography regularly without experiencing severe negative consequences, but also users who report negative consequences in their daily life resulting from their excessiveness of Internet pornography use. All other variables also had mean values that are comparable with those reported
Discussion
The results indicate specific brain responses to the presentation of preferred pornographic pictures compared to non-preferred pornographic pictures in the ventral striatum, a region associated with reward anticipation (Kühn and Gallinat, 2011, O'Doherty, 2004, Robbins and Everitt, 1996). Striatum activity has been consistently shown in the context of processing visual sexual material (cf., Georgiadis and Kringelbach, 2012, Gola et al., 2015, Sescousse et al., 2013, Stoléru et al., 2012) and
Conclusions
The results support a role for the ventral striatum in processing reward anticipation and gratification linked to subjectively preferred pornographic material. Ventral striatal reactivity was sensitive to personal preferences and explained variation in symptom severity. Thus, mechanisms for reward anticipation in ventral striatum may contribute to a neural explanation of why individuals with certain preferences and sexual fantasies are at-risk for losing their control over Internet pornography
Acknowledgments
We thank Dr. Fabian Grabenhorst for his valuable contributions to the study design and analyses.
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