Several studies have already highlighted the genetic predisposition to develop alcoholism in family history positive young offspring (Goodwin, 1979; Cotton, 1979; Begleiter et al., 1984; Schmidt and Neville, 1985; Porjesz and Begleiter, 1990; Kamarajan et al., 2005). The heritability of P3 amplitude has been reported to be high for both visual (Porjesz et al., 1998; Almasy et al., 1999 and auditory P3 O'Connor et al., 1994; Almasy et al., 1999). Many of the electrophysiological indices have served as endophenotypes for alcoholism (Porjesz et al., 2005; Frederick and Iacono, 2006). It is important that these indices demonstrate good heritability. In this regard, a large scale genomewide linkage study using the same semantic priming task showed significant heritabilities for N4 and P3 amplitude in response to primed and unprimed words. As for the P3 component, the N4 component too showed significant genetic correlations, indicating shared genetic influences. Suggestive evidence of linkage for N4 amplitudes has been noted in several chromosomal regions (Almasy et al., 1999; Almasy et al., 2001). Studies have shown decreased P3 amplitude in alcohol dependent individuals (Porjesz and Begleiter,
