Serotonin transporter gene promoter region polymorphism and selective processing of emotional images

Abstract

Several studies have now documented that the serotonin transporter promoter region (5-HTTLPR) polymorphism predicts neural response to affective images in brain regions involved in the experience of emotion. However, the behavioral consequences of this genetic effect are less well known. The current study used eye-tracking methodology to examine how individuals genotyped for the 5-HTTLPR allocated their attention when simultaneously presented an array of positive and negative emotional scenes. Short 5-HTTLPR allele homozygotes displayed a bias to focus on positive images, particularly in the first half of the 30s trial. In contrast, long 5-HTTLPR allele homozygotes viewed the stimuli in a more evenhanded fashion. Thus, short 5-HTTLPR allele homozygotes may be attempting to regulate greater reactivity to negative stimuli by purposefully turning their attention towards positive stimuli. Although this sensitivity may have benefits under benign conditions, it may also increase vulnerability to affective disorders when cognitive resources needed to turn attention away from negative stimuli are compromised.

Figure 1

An example of stimuli used in a trial with fixations superimposed on the image. Larger diameter of fixations indicates longer fixation duration. Numbers next to each fixation indicates sequence in which fixations occurred. Lines connecting fixations are intended to highlight the fixation sequence, but do not represent the actual scan path.

Figure 2

Percent of total fixation time viewing dysphoric, threat, positive, and neutral stimuli presented by 5-HTTLPR allele group (Panel A), and percent of total fixation time viewing positive stimuli across 5-second segments presented by 5-HTTLPR allele group (Panel B).