N4 abnormalities in semantic priming tasks have been observed in alcoholics. For example, Ceballos et al. (2005) found significantly less negative N4 amplitude in alcohol dependents relative to non-dependent controls. Similarly, Nixon et al. (2002) obtained reduced N4 amplitude of the difference waveform between primed and unprimed words in alcoholics compared to community controls. In a very large study, in contrast with controls, alcohol dependent subjects exhibited large N4 amplitudes to both primed and unprimed words alike (Porjesz et al., 2002), showing no attenuation of N4 for primed words; this indicates that alcoholics exhibit a lack of differentiation in their N4 responses between primed and unprimed words, responding similarly to both.
