Studies over the past few decades have found the amplitude of P3 to be significantly lower in abstinent alcoholics than in nonalcoholics (for a review, see Porjesz and Begleiter 1996). This deficit occurs most consistently in association with visual tasks and less consistently with auditory tasks. Researchers originally attributed these low P3 voltages to the cumulative toxic effects of alcohol on the brain. However, evidence increasingly indicates that this is not the case: P3’s remain low in alcoholics even after prolonged abstinence, including among members of Alcoholics Anonymous who have been abstinent for as long as 10 years (Porjesz and Begleiter 1985). Furthermore, low P3 amplitude appears to be related to the number of first-degree2 alcoholic relatives in the subject’s family, rather than to the subject’s own drinking history (e.g., quantity and frequency of consumption) (Pfefferbaum et al. 1991). These results suggest that rather than being a consequence of years of heavy drinking, low P3 amplitudes predate the development of alcoholism.
