AUDITORY P300 IN YOUNG ALCOHOLICS - REGIONAL RESPONSE CHARACTERISTICS

An auditory oddball paradigm was used to record the P300 component of the event-related potential (ERP) in a group of medication-free, chronic male alcoholics (n = 51, mean = 32.2) and a control group (n = 25, mean = 27.2), Each subject received a binaurally presented series of high (1600-Hz)- and low (600-Hz)-frequency tones. The designation of the rare tone (0.125 probability) was alternated across subjects. When the subject detected the rare tone, he made a button press as quickly as possible to record his reaction time. Scalp recordings using the entire 10/20 System, as well as interpolated placements, were made from 31 electrodes. For purposes of statistical analyses, five regional electrode groups were created: F (frontal), C (central), P (parietal), O (occipital), and T (temporal). The results of MANOVA indicated that control P300 amplitudes were significantly greater than those of the alcoholics in all five regions, whereas there were no P300 latency differences between groups in any region. Regional response differences between the groups were also compared with measures of surface energy (SE) (Wang et al., 1994), SE is a recently developed, reference-free global field measure that uses the entire scalp potential field and treats potentials at different positions differently. SE was significantly reduced in the alcoholics compared with the controls in both the C (p < 0.0003) and P (p < 0.0006) regions, although there were no differences in its distribution. Within the alcoholics, we identified a low-density (LD; n = 16) and high-density (HD; n = 22) subgroup based on the number of their alcoholic relatives (LD, no alcoholic relatives; HD mean = 4.4 alcoholic relatives/individual). Statistical analyses revealed that, in the O region, LD individuals had significantly larger P300 amplitudes than did HD individuals, Moreover, although there were no differences between LD and control P300 amplitudes in any region, HD subjects had significantly reduced P300 amplitudes compared with controls in every region. These findings suggest that genetic factors may contribute to the deficits observed. Moreover, these deficits may precede the onset of alcoholism and may function as critical phenotypic markers for its development.