The pharmacodynamic properties of lorazepam and methylphenidate drugs on event-related potentials and power spectral analysis in normal subjects.

The effect of lorazepam and methylphenidate on the ERPs and power spectral analysis was studied. Lorazepam caused prolonged latency and decreased amplitude of N200 and P300. This result suggests that lorazepam affects the neural processing of cognitive function. The drowsiness induced by lorazepam correlated inversely with alpha frequency power, but had no direct correlation with fast activity. On the contrary, when methylphenidate was given, there was no change in ERPs. There was an increase in percent alpha frequency correlated with the alertness of the subjects. An analysis of variance involving the factors of drug and time of rating showed that subjects showed a significant (p less than 0.0001) decrease in alertness over time while receiving lorazepam, and a significant (p less than 0.05) increase in alertness over time while receiving methylphenidate.