Variants of TPH2 interact with fast visual processing as assessed by metacontrast

Abstract

Sensitivity to threatening or otherwise unpleasant visual stimuli has become a widely used measure of potential vulnerability/resilience. Basically, experiments using this strategy present brief stimuli, often followed by a mask, and individuals' sensitivity is measured. However, it has not been asked whether the individual differences in threat detection or adaptive resilience associated with genetic variability-related endophenotypes might be just a function of some basic visual functions involved in processing and reporting brief visual stimuli without any emotional content. Effects attributed to emotional processing may be confounded by variability in simple basic visual skills. However, if simple visual skills are variable depending on common genetic variability, simple perceptual tests of screening for genetic risks can be developed. In a sample of normal human individuals, we studied the effects of a single nucleotide polymorphism (rs4570625) in the gene that encodes the rate-limiting enzyme in serotonin synthesis, TPH2, on metacontrast masking. Visual discrimination of target shapes that were incongruent with mask shapes was poorer in G homozygotes (typically considered more resilient individuals) compared with T-allele carriers and this effect was influenced by participants' sex. Implications for the development of psychophysical testing-based methods of screening for vulnerability/resilience in relation to the pathology of the serotonergic system-related dysfunction are considered.