• 5-HTTLPR;
  • amygdala;
  • classical conditioning;
  • imaging genetics;
  • fMRI;
  • positive emotion

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. Hum Brain Mapp 34:2549–2560, 2013. © 2012 Wiley Periodicals, Inc.