ERP responses to target and nontarget visual stimuli in alcoholics from VA and community treatment programs

This study had three aims: 1) to cross-validate previously reported findings that sober alcoholics compared to nonalcoholic peers have reduced ERP P300 amplitudes to visual target stimuli at the Pz electrode; 2) to test the hypothesis that alcoholics from VA Hospital treatment programs will manifest more ERP indications of brain dysfunction than peer alcoholics from community treatment programs (paralleling our neuropsychological findings in these samples); and 3) to explore differences among the groups in ERP responses to the little-studied nontarget stimuli. Nineteen VA alcoholics, 32 community alcoholics, and 24 peer community controls were given a visual "oddball" stimulus task. The total group of alcoholics had significantly lower P300 amplitudes than controls for target stimuli at the Pz electrode but VA and community alcoholic subgroups did not differ. There were no latency differences between or among the groups. On the nontarget stimuli, alcoholics had significantly higher P100 and lower N100 amplitudes than the controls at all three scored electrodes (Fz, Cz, and Pz). We conclude that cross-validation of reduced P300 amplitudes at Pz in sober alcoholics was obtained but that differences in severity of brain dysfunction, at least as measured by neuropsychological test performance, cannot account for alcoholics' ERP changes relative to controls. Finally, our data suggest that ERP changes to nontarget visual stimuli should be investigated in addition to the more traditional ERP measures to target stimuli.