Fig. 3.

Effect of ketamine on auditory-evoked potentials (AEPs) split by stimulus-onset asynchrony (SOA). Evoked potentials averaged across 6 frontocentral electrodes are plotted as a function of time from tone onset on the X axis. Colours correspond to different ranges of SOA, and line thickness corresponds to the standard error of the mean across trials. All 5 highlighted components show robust scaling of amplitude with SOA. This effect is less evident for P135 because it peaks on more posterior electrodes not represented in the 6 prefrontal electrodes averaged here. After administration of ketamine, this scaling with SOA is blunted, and in some cases completely abolished. Blunting is particularly pronounced for the N85 component. In addition, ketamine also reduces the duration of the N85 component and, as a result, its peak latency. The peak latencies of earlier components are not affected. Of note, the scaling of the P31 with SOA is largely resilient even to the highest dose (0.4 mg/kg) of ketamine.