Increased distractibility by task-irrelevant sound changes in abstinent alcoholics

Background: Chronic alcoholism is accompanied by "frontal" neuropsychologic al deficits that include an inability to maintain focus of attention. This might be associated with pronounced involuntary attention shifting to task- irrelevant stimulus changes and, thereafter, an impaired reorienting to the relevant task. The neural abnormalities that underlie such deficits in alc oholics were explored with event-related potential (ERP) components that di sclosed different phases of detection and orienting to stimulus changes. Methods: Twenty consecutive abstinent male alcoholics (DSM-TV) and 20 age-m atched male controls (healthy social drinkers) were instructed to discrimin ate equiprobable 100 and 200 msec tones in a reaction-time task (RT) and to ignore occasional, either slight (7%) or wide (70%), frequency changes (hy pothesized to increase RT) during an ERP measurement. Results: In the alcoholics, we found pronounced distractibility, evidenced by a RT lag (p < 0.01) caused by deviants, that correlated (Spearman <rho> = 0.5) with a significantly enhanced (p < 0.01) amplitude of mismatch negat ivity (MMN) to deviants. Significantly increased RT lag for trials subseque nt to deviants (slight p < 0.001, wide p < 0.05) in the alcoholics suggeste d impaired reorienting to the relevant task. The MMN enhancement also predi cted poorer hit rates in the alcoholics (Spearman <rho> = 0.6-0.7). Both th e MMN enhancement and pronounced distractibility correlated (Spearman rho = 0.4) with an early onset of alcoholism. Conclusions: Attentional deficits in the abstinent alcoholics were indicate d by the increased distractibility by irrelevant sound changes. The MMN enh ancement suggested that this reflects impaired neural inhibition of involun tary attention shifting, being most pronounced in early-onset alcoholics.