Neurobiological Basis of Hypersexuality (2016)
COMMENTS: While a good overview, it omitted many of the studies collected on this page: Brain Studies on Porn Users. Perhaps the paper was submitted prior to the studies publication. In addition, the review doesn't separate "hypersexuality" from internet porn addiction. That said, the conclusion is pretty clear:
"Taken together, the evidence seems to imply that alterations in the frontal lobe, amygdala, hippocampus, hypothalamus, septum, and brain regions that process reward play a prominent role in the emergence of hypersexuality. Genetic studies and neuropharmacological treatment approaches point at an involvement of the dopaminergic system."
- * University Clinic Hamburg-Eppendorf, Clinic and Polyclinic for Psychiatry and Psychotherapy, Hamburg, Germany
- † Center for Lifespan Psychology, Max Planck Institute for Human Development, Berlin, Germany
Available online 31 May 2016
Until now, hypersexuality has not found entry into the common diagnostic classification systems. However it is a frequently discussed phenomenon consisting of excessive sexual appetite that is maladaptive for the individual. Initial studies investigated the neurobiological underpinnings of hypersexuality, but current literature is still insufficient to draw unequivocal conclusions. In the present review, we summarize and discuss findings from various perspectives: neuroimaging and lesion studies, studies on other neurological disorders that are sometimes accompanied by hypersexuality, neuropharmacological evidence, genetic as well as animal studies. Taken together, the evidence seems to imply that alterations in the frontal lobe, amygdala, hippocampus, hypothalamus, septum, and brain regions that process reward play a prominent role in the emergence of hypersexuality. Genetic studies and neuropharmacological treatment approaches point at an involvement of the dopaminergic system.
Keywords: Sex addiction; Compulsive sexual behavior; Hypersexuality; Excessive nonparaphilic sexual behavior
A FEW EXCERPTS
4. NEUROIMAGING CORRELATES OF HYPERSEXUALITY
Multiple studies have investigated the neural correlates of sexual arousal in response to visual erotic stimuli in comparison to neutral stimuli using functional magnetic resonance imaging (fMRI). In a meta-analysis on multiple neuroimaging studies investigating brain responses to visual erotic cues conducted in male heterosexuals, we found convergence across studies in BOLD activation in several regions including hypothalamus, thalamus, amygdala, anterior cingulate gyrus (ACC), insula, fusiform gyrus, precentral gyrus, parietal cortex, and occipital cortex (Kuhn & Gallinat, 2011a) (Fig. 1). In studies that reported brain responses associated with a physiological marker of sexual arousal (eg, penile tumescence), we found consistent activation across studies in hypothalamus, thalamus, bilateral insula, ACC, postcentral gyrus, and occipital gyrus. Lateral frontal cortex Medial frontal cortex Temporal cortex Anterior cingulate cortex Cuadate Thalamus Amygdala Hippocampus Insula Nucleus accumbens Hypothalamus. Fig. 1 Regions potentially involved in hypersexual behaviors (septum not shown).
In studies in which brain activity was monitored during orgasm for men and women, activation was reported in dopaminergic pathways originating from the ventral tegmentum (VTA) (Holstege et al., 2003) to the nucleus accumbens (Komisaruk et al., 2004; Komisaruk, Wise, Frangos, Birbano, & Allen, 2011). Activity was also observed in cerebellum and the ACC (Holstege et al., 2003; Komisaruk et al., 2004, 2011). In women only, frontal cortical brain activation was observed during orgasm (Komisaruk & Whipple, 2005). In a cue-reactivity study on cocaine-addicted patients, individuals were presented with visual cues related to either cocaine or sex (Childress et al., 2008). Interestingly, the results revealed similar brain regions to be activated during drug-related and sex-related cues located in the reward network and the limbic system, namely in VTA, amygdala, nucleus accumbens, orbitofrontal, and insular cortex. Others have remarked a similarity in the cerebral activation profile in response to sexual stimuli and love and attachment (Frascella, Potenza, Brown, & Childress, 2010).
Only a single study to date has, to our knowledge, investigated differences in brain activation between participants with and without hypersexuality during a cue-reactivity fMRI task (Voon et al., 2014). The authors report higher ACC, ventral striatal, and amygdala activity in individuals with hypersexuality compared with those without. The areas activated overlap with brain regions that we identified in a meta-analysis to be consistently activated in drug-craving paradigms across different types of substance addictions (K€uhn & Gallinat, 2011b). This regional similarity offers furthersupport for the hypothesis that hypersexuality may indeed be most similar to addiction disorders. The study by Voon and colleagues also revealed that high functional connectivity of the ACC–striatal–amygdala network was associated with subjectively reported sexual desire (“wanting” in reply to the question “How much did this increase your sexual desire?” not “liking” assessed by the question “How much did you like this video?”) to a higher degree in patients with hypersexuality. Moreover, the patients with hypersexuality reported higher levels of “wanting” but not of “liking.” This dissociation between “wanting” and “liking” has been hypothesized to occur once a certain behavior becomes an addiction within the framework
of the so-called incentive-salience theory of addiction (Robinson & Berridge, 2008).
In an electroencephalography study on participants complaining about difficulties in controlling their consumption of internet pornography, event related potentials (ERPs), namely P300 amplitudes in response to emotional and sexual cues, were tested for an association with questionnaire scores assessing hypersexuality and sexual desire (wanting) (Steele, Staley, Fong, & Prause, 2013). The P300 has been related to attentional processes and is in part generated in the ACC. The authors interpret the absence of a correlation between questionnaire scores and ERP amplitudes as a failure to support previous models of hypersexuality. This conclusion has been criticized as unjustified by others (Love, Laier, Brand, Hatch, & Hajela, 2015; Watts & Hilton, 2011).
In a recent study by our group, we recruited healthy male participants and associated their self-reported hours spent with pornographic material with their fMRI response to sexual pictures as well as with their brain morphology (Kuhn & Gallinat, 2014). The more hours participants reported consuming pornography, the smaller the BOLD response in left putamen in response to sexual images. Moreover, we found that more hours spent watching pornography was associated with smaller gray matter volume in the striatum, more precisely in the right caudate reaching into the ventral putamen. We speculate that the brain structural volume deficit may reflect the results of tolerance after desensitization to sexual stimuli. The discrepancy between the results reported by Voon and colleagues could be due to the fact that our participants were recruited from the general population and were not diagnosed as suffering from hypersexuality. However, it may well be that still pictures of pornographic content (in contrast to videos as used in the study by Voon) may not satisfy today’s video porn viewers, as suggested by Love and colleagues (2015). In terms of functional connectivity, we found that participants who consumed more pornography showed less connectivity between the right caudate (where the volume was found to be smaller) and left dorsolateral prefrontal cortex (DLPFC). DLPFC is not only known to be involved in executive control functions but also known to be involved in cue reactivity to drugs. A specific disruption of functional connectivity between DLPFC and caudate has likewise been reported in heroin-addicted participants (Wang et al., 2013) which makes the neural correlates of pornography similar to those in drug addiction.
Another study that has investigated the structural neural correlates associated with hypersexuality used diffusion tensor imaging and reported higher mean diffusivity in a prefrontal white matter tract in a superior frontal region (Miner, Raymond, Mueller, Lloyd, & Lim, 2009) and a negative correlation between mean diffusivity in this tract and scores in a compulsive sexual behavior inventory. These authors likewise report more impulsive behavior in a Go-NoGo task in hypersexual compared with control participants.
Comparable inhibitory deficits have been demonstrated in cocaine-, MDMA-, methamphetamine-, tobacco-, and alcohol-dependent populations (Smith, Mattick, Jamadar, & Iredale, 2014). Another study that investigated brain structure in hypersexuality by means of voxel-based morphometry might be of interest here, although the sample consisted of frontotemporal dementia patients (Perry et al., 2014). The authors report an association between right ventral putamen and pallidum atrophy and reward-seeking behavior. However, the authors correlated gray matter with a reward-seeking score that included other behavioral variants such as overeating (78%), increased alcohol or drug use (26%), in addition to hypersexuality (17%).
To summarize, the neuroimaging evidence points at an involvement of brain areas related to reward processing, including the nucleus accumbens (or more generally the striatum) and the VTA, prefrontal structures as well as limbic structures such as the amygdala and the hypothalamus in sexual arousal and potentially also hypersexuality.