Resistance to extinction in appetitive and aversive conditioning of the sexual response

Having too little sexual desire is the most common sexual problem among women
(Mercer et al., 2003; Simons & Carey, 2001). American and English nationwide
studies report a lifetime prevalence of 30-40%, and a prevalence of 10% for
persistent low sexual desire problems (Laumann, Paik, Rosen, 1999). A low level
of desire is usually accompanied by a low level of sexual arousal, and
frequently associated with sexual dissatisfaction (Basson, 2007). Excessive
sexual desire, or hyperactive sexual desire, is mostly observed in men, and
appears to be associated with paraphilia-related disorders (Kafka, 2007). Both
hypo- and hyperactive sexual desire can cause marked personal distress and
marital discord, and hypersexuality is a serious social problem when it
develops into sexually abusive behavior. Very little is known about causes of
hypo- and hyperactive sexual desire disorders, and for both empirically
validated treatments are lacking (Kafka, 2007; ter Kuile, Both, van Lankveld,
2009). Insight in the underlying mechanisms of sexual motivation is essential
to understand these disorders, and is needed to guide prevention as well as
psychological and/or pharmacological treatment thereof. Sexual behaviour,
particularly orgasm, is regarded as a rewarding event, which can reinforce
learning (Agmo, 1999). The positive affect produced by sexual stimulation can
become associated to environmental stimuli, and these stimuli can thereby
become conditioned sexual incentives. Repeated exposure to the same stimuli
while experiencing sexual reward will enhance the strength of conditioning, and
the intensity of the experienced reward will probably determine the incentive
properties of the conditioned stimuli (Agmo et al., 2004). By contrast,
negative emotional experiences, or the absence of expected positive
experiences, may also become associated with stimuli that used to have
incentive value, resulting in less attraction or even aversion to these
incentives. In the aetiology of sexual desire disorders conditioning may play a
pivotal role; for instance low desire may be caused by a lack of association
between sexually rewarding experiences and stimuli, resulting in a limited
number of potential sexual incentives, and it may be caused by negative sexual
experiences that changed the initial positive valence of sexual incentives into
a negative one.
The present study investigates the process through which stimuli become cues
for sexual reward and acquire motivational value (appetitive conditioning) and
how stimuli become cues for punishment and acquire a negative value (aversive
conditioning). The aim of the proposal is to study mechanisms that may
facilitate or impair sexual response. Although many theories of human sexual
behavior assume that sexual stimuli obtain arousing properties through
associative learning (Hardy, 1964; Byrne, 1986), systematic research on sexual
reward learning is largely limited to studies in animals, mainly rats (Pfaus,
Kippin, Centeno, 2001). In these studies, the paradigm of classical
conditioning is often used in which a specific stimulus (the *conditional*
stimulus, or CS), for example a smell, is repeatedly paired with stimulation
eliciting sexual response (the *unconditional* stimulus, or US). After pairing,
the particular smell is in itself able to elicit a sexual response (the
*conditioned* response, or CR). Following conditioning, the CS can be
repeatedly presented without US to study extinction of the conditioned
response. Such experimental procedures are used to systematically investigate
sexual reward learning and neurobiological influences on this learning (Pfaus,
Kippin, Centeno, 2001). This kind of research in humans is extremely scarce,
especially in women, while it is likely to yield important knowledge about
mechanisms underlying sexual motivation and related disorders such as hypo- and
hypersexuality.

The purpose of this study is to investigate basal sexual conditioning
mechanisms among healthy males and females. This study will investigate how
stimuli acquire or lose sexually rewarding properties. This knowledge may help
in the treatment of sexual motivation disorders such as too little and
excessive sexual desire. Generally, it is assumed that in these disorders
sexual reward learning by classical conditioning plays an essential role. In
humans, however, experimental research on sexual reward learning is scarce. In
this research, basic phenomena such as extinction in sexual conditioning will
be studied in humans. We suppose that repeated associations between a neutral
stimulus and sexual stimulation results, through classical conditioning, in a
learned appetitive sexual response to this stimulus. In a comparable manner,
repeated associations between a sexual erotic stimulus and painful stimulation
results, also through the mechanism of classical conditioning, in a learned
aversive sexual response to this stimulus. Following conditioning, the stimulus
can be repeatedly presented without the unconditional stimulus (e.g. the sexual
erotic or painful stimulation) to study extinction of the conditioned response.
Such experimental procedures can be used to systematically investigate sexual
reward learning. This kind of research in humans is extremely scarce, while it
is likely to yield important knowledge about mechanisms underlying sexual
motivation and related disorders such as hypo- and hypersexuality. Previous
studies have shown that appetitively and aversively conditioned genital
responses and subjective affect did not extinguish significantly during the
extinction phase, suggesting resistance to extinction. Subsequently, resistance
to extinction of conditioned sexual responses may have important clinical
implications.

The experimental design involves differential conditioning with one stimulus
(the CS+) being followed by the sexual appetitive US during the conditioning
phase, whereas another stimulus (the CS-) never is followed by the US. Which
neutral stimulus is paired with the sexual appetitive stimulus is
counterbalanced among subjects. In the acquisition phase, in which the CS+ and
CS- are presented 10 times each, the CS+ is always immediately followed by the
US. During the subsequent extinction phase, the CS+ and CS- will be presented
24 times each. Thus, the basic design in this study is a 2 (stimulus; CS+
versus CS-) x 48 (trial) design with stimulus and trial as within-subjects
variables.
The design for the aversive conditioning study is comparable to experiment 1
and is also a 2 (erotic stimulus; CS+ versus CS-) x 48 (trial) design with
stimulus and trial as within-subjects variables. Similar to experiment 1, which
of the two pictures served as the CS+ or the CS- will be counterbalanced.

The visit to the LUMC will take approximately 2 hours. There are nor isks
associated with participation in this study. The apllication of the painful
stimulus is harmless, but can be perceived as inconvenient.