Acute and chronic effects of alcohol on preattentive auditory processing as reflected by mismatch negativity

Chronic alcoholism, a major worldwide health problem, is associated with a variety of neurocognitive changes in the afflicted individuals. The precise neurophysiological basis of these changes is not yet understood. Mismatch negativity (MMN) is a preattentive event-related potential component indexing cortical auditory memory traces and automatic change detection in the brain that can be used to study the neural basis of cognitive impairments in various neurodegenerative diseases. MMN studies have revealed that even a low dose of acute alcohol significantly impairs automatic change detection and involuntary attention shifting. Recent MMN results on chronic alcoholism in turn suggest that auditory sensory traces decay slightly faster and are substantially more vulnerable to the distracting effect of backward masking in alcoholics than in healthy subjects. Furthermore, chronic alcohol abuse might accelerate the age-related impairment of automatic change detection. There is also evidence that the MMN changes might predict impaired performance in behavioral memory and attention tasks in alcoholics. In MMN studies of detoxified alcoholics, however, many confounding factors have to be taken into account. For instance, postwithdrawal brain hyperexcitability might be associated with a slightly enhanced or accelerated MMN/MMNm (the magnetic equivalent of MMN). In sum, MMN and MMNm provide an objective noninvasive tool for exploring the neurophysiological functional deficits related to both acute alcohol intoxication and chronic alcoholism.