In one experiment (Porjesz and Begleiter 1979), alcoholics who had been abstinent for an average of 1 month were presented with sequences of random single flashes and single clicks interspersed with more rarely occurring double flashes and double clicks. For each sequence, subjects were instructed to count either the double flashes or double clicks or else to ignore all stimuli in the sequence. ERP’s were recorded only to the frequent single flashes, which were either in the relevant channel (when double flashes were counted) or the irrelevant channel (when double clicks were counted). Alcoholics maintained a low amplitude of N1 regardless of channel relevance, thereby exhibiting small or absent Nd components. These results suggest that alcoholics do not differentiate between relevant and irrelevant sensory channels.
