Another rapidly developing area of genetic research is concerned with epigenetic modifications of gene expression through DNA methylation and histone modifications that can lead to long-lasting changes of the phenotype. These epigenetic processes can be triggered by exposure to both physical and psychosocial factors (Fraga et al., 2005; Wong et al., 2010). Epigenetic differences have been documented in MZ twins (Kaminsky et al., 2009); these differences are already present in children (Wong et al., 2010) and tend to accumulate with age (Fraga et al., 2005; Poulsen et al., 2007). Investigation of epigenetic characteristics in twin pairs discordant for a phenotype of interest (e.g. EEG or specific ERP response) can shed light on the role of epigenetic factors in brain development and shaping individual differences in neurocognitive functioning.
