br Discussion The present study investigated the relationshi

Discussion The present study investigated the relationship between the 5-HTTLPR polymorphism and neural mechanisms of selective auditory attention in preschool children from lower SES backgrounds. We observed clear differences in a neural index of selective attention as a function of the 5-HTTLPR genotypes. Specifically, short allele carriers exhibited a larger effect of selective attention on ERPs compared to long homozygotes. In contrast, no differences were observed between children carrying one versus two copies of the short allele. As previous research indicates that larger effects of selective attention on ERPs are linked to better performance in nonverbal tasks of cognition in adults and children (Giuliano et al., 2014; Isbell et al., 2016), this hdac inhibitor suggests that the current findings can be interpreted as enhanced neural mechanisms of selective attention in short allele carriers. The enhanced ERP attention effects in short carriers were broadly distributed across the scalp, with no evidence that the group effects were specific to more anterior versus posterior electrode sites. Indeed, although the source of attentional modulation is expected to be an anterior fronto-parietal network, including the PFC, our dependent measure captures the effects of that network on the underlying sensory processing. While previous research on ERP auditory selective attention effects suggests that anterior and central attention effects correlate most strongly with nonverbal IQ (Isbell et al., 2016), no such specificity was observed here. However, the overall distribution of the effect is consistent with previous research using the same dichotic listening paradigm, which showed that the ERP auditory selective attention effects in typically developing preschool aged children are broadly distributed across the scalp (Karns et al., 2015; Sanders et al., 2006). In addition, a supplemental analysis ruled out the possibility that short allele carriers simply showed generalized heightened neural activity, which would have been manifest as group differences regardless of attention condition (i.e., larger overall ERP amplitudes). Thus, our findings suggest an enhancement of the ERP attention effect in short allele carriers, which in preschool children is broadly distributed across the scalp. Our results provide initial evidence for a relation between serotonergic systems, as indexed by the 5-HTTLPR polymorphism, and neural mechanisms of selective attention in young children. Given the critical role of PFC as a source of top-down attentional modulation (Petersen and Posner, 2012; Squire et al., 2013), it is plausible that this relation between serotonergic systems and selective attention is mediated by the structural and functional links between serotonergic systems and PFC (Andrade, 2011; Lesch and Waider, 2012; Puig and Gulledge, 2011). However, the ways in which the allelic variations of 5-HTTLPR contribute to brain functioning is still under investigation (Iurescia et al., 2015). Therefore, the precise neurobiological mechanisms that lead to enhanced selective attention in short allele carriers are to be determined. Most previous research has examined 5-HTTLPR in relation to biased attention toward stimuli with emotional valence (for a review, see Pergamin-Hight et al., 2012). The most robust finding of these studies is that the short allele is associated with attentional bias toward positive valence, such as happy faces (Beevers et al., 2009; Fox et al., 2011), as well as negative emotional expressions, such as anger, fear, or sadness (Beevers et al., 2009; Fox et al., 2011; Lonsdorf et al., 2014; Thomason et al., 2010) or fear-relevant stimuli, such as spiders (Osinsky et al., 2008). The associations between the short allele and greater biased attention to negative valence are also observed in interaction with stressful life events and low social support (Jenness et al., 2015; Pearson et al., 2016). This greater attentional bias toward emotionally or socially salient stimuli in short allele carriers has been mainly discussed as a potential pathway of vulnerability toward affective disorders, such as depression and anxiety.