In contrast, not many studies have examined semantic processing substrates in the context of alcohol dependence. A negative peak in the ERP (designated as N400) occurring predominantly over the centroparietal scalp region and approximately 300 to 650 ms after the presentation of a word that is incongruent with its semantic context, has been the cornerstone of semantic processing studies (Bentin, 1989; Bentin et al., 1993; Gunter and Friederici, 1999; Hamberger et al., 1995; Kutas and Hillyard, 1980; Nixon et al., 2002). Classically it was understood to be elicited only to semantic violations (Kutas and Hillyard, 1980; Kutas and Van Petten, 1988; Nixon et al., 2002), but recent studies have shown that the N400 varies systematically with the processing of potentially meaningful stimuli, where the amplitude is reduced by a number of factors (Kutas and Federmeier, 2000); some of these factors are semantic congruity, antonyms, repetitions and stimuli that occur with high frequency (Brown and Hagoort, 1993; Fischler et al., 1983; Kutas and Federmeier, 2000; Nobre and McCarthy, 1995; Penke et al., 1997).
