In a visual oddball paradigm, evoked delta and theta power while processing the target stimuli is significantly decreased among alcoholics compared with control subjects (see figures 2B and 2C), indicating that the reduced P3 amplitudes reported in alcoholics are caused by deficits in theta and delta oscillations that underlie P3. In a Go/No-Go paradigm, alcoholics also manifested significantly decreased delta and theta power, particularly during No-Go processing (Kamarajan et al. 2004). An increase in theta power is related to an increase in theta in the hippocampus, known to be an inhibitory rhythm associated with GABAergic activity (Klimesch et al. 2000). An increase in theta is associated with inhibition of nonrelevant information while attending to relevant information (e.g., a target stimulus). As most information is irrelevant and must be suppressed, this yields the high amplitude of P3 to relevant stimuli. Hence the deficit in inhibitory theta oscillations underlying P3 in alcoholics suggests deficient inhibitory control during information processing (e.g., attention and memory mechanisms) in alcoholics. This finding provides further support for the hypothesis that CNS disinhibition is involved in alcoholism (Begleiter and Porjesz 1999).
