Further evidence for TF activity’s utility as an endophenotype comes from studies linking P3-related delta and theta activity to specific genes: CHRM2 (Jones et al., 2004; Porjesz & Rangaswamy, 2007), a cholinergic muscarinic receptor gene, and GRM8 (Chen et al., 2009), a metabotropic glutamate receptor gene, both on chromosome 7. Both CHRM2 and GRM8 have been associated with alcohol dependence (Chen et al., 2009; Luo et al., 2005; Wang et al., 2004), while CHRM2 has also been implicated in drug dependence (Luo et al., 2005; Wang et al., 2004), and, most recently, in externalizing disorders (Dick et al., 2008).
