Background: Although it is widely accepted that serotonin plays a pivotal role in emotional perception and processing, the role of serotonin in cognition is less clear. The present study investigated the implications of introducing emotional faces in a measure of cognitive control functioning. The measure was explored in association with the serotonin transporter polymorphism (5-HTTLPR), linked to serotonin transmission in the brain. An integrative model of emotional processing was used to illustrate cognitive control functioning in emotional processing and potential 5-HTTLPR-dependent diatheses for depressive symptomatology. As previous studies have shown the effect of sex on the relationship between 5-HTTLPR subtypes and cognitive measures, we also included sex as a variable in our analyses.
Methods: Sixty healthy participants were recruited in an experimental design. The participants underwent an extensive screening procedure and gave blood samples for 5-HTTLPR analysis. A new computerized test, labeled the Emo n-back, was constructed to explore the implications of presenting emotional categories of human faces in a paradigm measuring aspects of cognitive control functioning. Emotional categories within the Emo n-back were analyzed to spot 5-HTTLPR-dependent variation in cognitive and emotional perception and processing in males and females.
Results: Exposure to different emotional categories had specific effects on cognitive control functions as measured by the Emo n-back. Participants showed significantly decreased accuracy on the n-back task when presented with successive images from the negative emotional categories, and this effect was most pronounced for sad compared with neutral faces. A three-way interaction effect was found between sex, 5-HTTLPR polymorphism and emotional categories within the Emo n-back. Examination of this interaction revealed a distinct pattern for female short 5-HTTLPR carriers indicating an increased sensitivity to the sad emotional category in this subgroup of participants.
Conclusion: Sex and 5-HTTLPR polymorphism had a significant impact on accuracy in a measure of cognitive control function. The effect is most pronounced when presented with sad human faces, indicating altered sex- 5-HTTLPR-dependent processing linked to specific emotional content. The Emo n-back indicated mechanisms that might represent diatheses for depressive symptomatology by demonstrating the different genotypes to reveal distinct patterns in the way they process adverse environmental stimuli.