The usefulness of P300 amplitude as an endophenotype for AD risk is strengthened by observations that P300 amplitude is heritable (O’Connor et al., 1994; Katsanis et al., 1997; van Beijsterveldt, 2002; Carlson and Iacono, 2006; Perlman et al., 2009). A search for specific genes influencing these oscillations has been of considerable interest and has resulted in reports of positive associations for visual P300 and a dopamine D2 receptor locus on chromosome 11 (Hill et al., 1998), SNPs within the CHRM2 gene on chromosome 7 (Jones et al., 2004; Jones et al., 2006), and GABRA2 variation on chromosome 4 (Porjesz and Rangaswamy, 2007).
