We have previously suggested that low doses of ethanol may produce effects on multiple brain systems by introducing an increased level of noise or randomness in neuronal processing as indexed by a decrease in nonlinear structure in the cortical EEG (Ehlers, 1992; Ehlers et al., 1998b). In our previous studies, using a different data set, we demonstrated that several of the measures that formally index nonlinear structure provided evidence to suggest that EEG collected during mild alcohol intoxication in young men has less nonlinear structure than EEG data collected after placebo consumption (Ehlers et al., 1998b). Measures of EEG determinism, space-filling properties of the attractor, and redundancy were also found to be predictive of the level of intoxication as reported by the subject (Ehlers et al., 1998b). Linear measures of the EEG (EEG spectra), on the other hand, failed to be predictive of the behavioral measures of intoxication. These findings, together with the present data demonstrating that ethanol reduces phase locking of EROs, are consistent with the hypothesis that low doses of ethanol increase the noise level in neuronal processing at the level of the EEG leading to its behavioral effects.
