Not only do alcoholics manifest low amplitude P3b components in response to target stimuli, they also manifest low P3a components in response to rare nontargets in both visual and auditory modalities. Recent reports have indicated that alcoholics manifest reduced P3 amplitudes to both Go (target) and No-Go (rare nontarget) stimuli. Furthermore, alcoholics manifest less differentiation between their responses to target and nontarget stimuli. In keeping with various neurophysiological explanations of the P3 component (Desmedt 1980; Verleger 1988; Birbaumer et al. 1990; Rockstroh et al. 1992; Klimesch et al. 2000), the amplitude of P3 is thought to reflect CNS inhibition (the larger the P3, the greater the inhibition). An increase in theta power, an inhibitory rhythm, underlies P3 (see the following section on event-related oscillations). Most information a person is exposed to is irrelevant and must be suppressed while the person selectively responds to the relevant information; this accounts for the large amplitude of the P3 (Klimesch et al. 2000). The low-amplitude P3 components manifested by alcoholics indicate that they have less CNS inhibition than control subjects. Researchers have hypothesized that
