Ethanol-induced alterations in EEG alpha activity and apparent source of the auditory P300 evoked response potential

The relationship among topographic brain electrical activity mapping, auditory-evoked response potentials (ERPs), plasma ethanol levels and subjective reports of intoxication was examined in 4 male volunteers. The source of the auditory P300 ERP (a measure of selective attention and memory encoding) was estimated using a recently developed computer program. The effect of ethanol on the P300 wave was studied using a standard oddball paradigm both with and without a concomitant divided attention task. Ethanol (0.7 g/kg) administration produced marked increases in EEG alpha activity during the ascending limb of the blood ethanol curve. Acute ethanol administration caused a delay in the latency and a reduction in the amplitude of the auditory P300 ERP. A similar effect on P300 topography was noted in waves that were affected by the tones while the subjects also listened to a story (divided attention). After ethanol, the source of the P300 wave appeared to have shifted to a position posterior and inferior to its original location. P300 ERP's generated during the divided attention task were also disrupted and shifted to positions inferior to their original. However, the variability of the dipole vector was much greater during the divided attention task than after ethanol administration. These data demonstrate that ethanol's effects on cognitive processing skills may be similar to those produced when individuals experience distractions while concentrating on a task.