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  • Klucken, T., Wehrum, S., Schweckendiek, J., Merz, C. J., Hennig, J., Vaitl, D., & Stark, R. (2013). The 5-HTTLPR polymorphism is associated with altered hemodynamic responses during appetitive conditioning. Human Brain Mapping, 34(10), 2549–2560. https://doi.org/10.1002/hbm.22085

    BACKGROUND: Current models suggest that a variation in the promoter region of the serotonin transporter gene (5-HTTLPR) is associated with altered amygdala reactivity not only towards negative but also towards positive stimuli, which has been neglected in the past. This association may possibly convey an elevated vulnerability for psychopathology like abuse, craving, and relapses. Since appetitive conditioning is a crucial mechanism in the pathogenesis of these psychiatric disorders, the identification of specific factors contributing to interindividual variation is important. METHODS: In the present study (N = 86), an appetitive conditioning paradigm was conducted, in which a neutral stimulus (CS+) was associated with appetitive stimuli, while a second stimulus (CS-) predicted their absence. Subjects were genotyped according to the 5-HTTLPR genotype. RESULTS: As the main result, we report a significant association between the 5-HTTLPR genotype and hemodynamic responses. Individuals with the s-allele displayed elevated conditioned bilateral amygdala activity in contrast to l/l-allele carriers. Further, increased hemodynamic responses in s-allele carriers were also found in the extended emotional network including the orbitofrontal cortex, the thalamus, and the ventral striatum. CONCLUSION: The present findings indicate an association of the 5-HTTLPR and altered conditioned responses in appetitive conditioning. Further, the findings contribute to the ongoing debate on 5-HTTLPR dependent hemodynamic response patterns by emphasizing that s-allele carriers are not exclusively biased towards fearful, but also towards positive stimuli. In conclusion, our results imply that s-allele carriers might be better described as hyper-reactive towards salient stimuli, which may convey vulnerability for the development of psychiatric disorders.

  • Kagerer, S., Klucken, T., Wehrum, S., Zimmermann, M., Schienle, A., Walter, B., Vaitl, D., & Stark, R. (2011). Neural activation toward erotic stimuli in homosexual and heterosexual males. The Journal of Sexual Medicine, 8(11), 3132–3143. https://doi.org/10.1111/j.1743-6109.2011.02449.x

    INTRODUCTION: Studies investigating sexual arousal exist, yet there are diverging findings on the underlying neural mechanisms with regard to sexual orientation. Moreover, sexual arousal effects have often been confounded with general arousal effects. Hence, it is still unclear which structures underlie the sexual arousal response in homosexual and heterosexual men. AIM: Neural activity and subjective responses were investigated in order to disentangle sexual from general arousal. Considering sexual orientation, differential and conjoint neural activations were of interest. METHODS: The functional magnetic resonance imaging (fMRI) study focused on the neural networks involved in the processing of sexual stimuli in 21 male participants (11 homosexual, 10 heterosexual). Both groups viewed pictures with erotic content as well as aversive and neutral stimuli. The erotic pictures were subdivided into three categories (most sexually arousing, least sexually arousing, and rest) based on the individual subjective ratings of each participant. MAIN OUTCOME MEASURES: Blood oxygen level-dependent responses measured by fMRI and subjective ratings. RESULTS: A conjunction analysis revealed conjoint neural activation related to sexual arousal in thalamus, hypothalamus, occipital cortex, and nucleus accumbens. Increased insula, amygdala, and anterior cingulate gyrus activation could be linked to general arousal. Group differences emerged neither when viewing the most sexually arousing pictures compared with highly arousing aversive pictures nor compared with neutral pictures. CONCLUSION: Results suggest that a widespread neural network is activated by highly sexually arousing visual stimuli. A partly distinct network of structures underlies sexual and general arousal effects. The processing of preferred, highly sexually arousing stimuli recruited similar structures in homosexual and heterosexual males.

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