Another important direction of research for genetic psychophysiology in coming years will be functional characterization of genes implicated in psychological and psychiatric phenotypes. Generally speaking, two alternative approaches to the study of the genotype-phenotype relationships can be distinguished. The first one is the currently dominating top-down, phenotype-centered approach that identifies a phenotype of interest and asks the question: what genes influence this phenotype? In contrast, the bottom-up, gene-centered approach starts with a specific genetic polymorphism and asks the question: what are the phenotypic effects of this genetic variation? Few studies have taken the latter strategy, but it can be anticipated that the ongoing GWAS studies of psychiatric phenotypes will identify important causal variants conferring susceptibility to disorder, but very little may be known about the mechanisms of their action. de Geus has recently proposed that testing the association of the newly identified risk alleles with EEG and ERP endophenotypes can help us understand “where in the brain, in which stage, and during what type of information processing the genetic variant has a role”(de Geus, 2010). Importantly, such testing would require
